Continental XO-1430 Development
Part 14: 1940 and Conclusion
by Kimble D. McCutcheon
Published 15 Nov 2025

5 Jan 1940. The reports previously submitted by Air Corps Inspector Robert P. Triggs were now being submitted by Joseph Haddad, a MatCmd Junior Mechanical Engineer assigned to CMC. Haddad reported that O-1430-1 had been run at 3,000 rpm and rated manifold pressure while the exhaust back pressure was varied. The power output varied from 993.5 hp at 0 inHgG back pressure to 962 hp at 9.3 inHgG back pressure. The engine was run at 3,000 rpm and 800 hp; at 0 inHgG back pressure it developed 802 hp and at 6.5 inHgG back pressure, 788 hp. The engine was also run from 1,800 rpm to 3,200 rpm and from 0 inHgG to full throttle. These runs were made at best-power mixture setting. The O-1430-1 had run 73:18 hrs on Contract W-535-AC-12741, of which 31:18 were on the new crankcase.

No official twin-cylinder runs had been made during this reporting period. Difficulty with the boost pressure controls and broken tubes on the fuel/air ratio indicator had curtailed testing. No provisions had been made to measure maximum pressure as called for in Contract W-535-AC-12741 Item 4. The crankpin bearing failed on 5 January leaving a slight lead-bronze deposit on the forked rod but none on the blade rod. Both rods were blue at the crank end and appeared to have been drawn. However, this condition indicated failure by pounding rather than by burning out. CMC had decided to replace both rods and bearings in order that any future failure could not be blamed on this particular failure. Total twin-cylinder engine time was 53:30 hrs of which 29:15 hrs were firing. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 89 – 90.]

11 Jan 1940. Haddad reported that the O-1430-1 Nos. 3 and 4 crankpin bearings had failed in a similar manner to the twin-cylinder failure reported on 5 January. The O-1430-1 failure occurred after a 4:14-hr run-in on a new piston that had replaced a scored one. Bearing inspection before the run showed no wear, but after the run, the dowel pins in the forked rods that fixed the bearing positions had sheared and the crankshaft was apparently sprung. The connecting rods were in better shape than the twin-cylinder rods. Both crankpins required grinding and the bearings would need replacement. As both engines on Contract W-535-AC-12741 were under repair, no official runs were to be made for the next two weeks. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 91.]

P14 Curve No. 18

15 Jan 1940 Progress Report. After a short run-in during which the power was checked against data submitted in the 15 Jun 1939 Progress Report, O-1430-1 power versus manifold pressure was determined at 3,000, 2,800, 2,600, 2,400, 2,200, 2,000 and 1,800 rpm. The manifold pressure was varied in approximately 4 inHgG increments, the spark advance was set for best power, and in all cases except 3,200 rpm the mixture was set for best power. Results appear in Curve No. 18. It was noteworthy that power was less at 3,200 rpm than at 3,000 rpm; this may have been due to an overly rich mixture, malfunctioning spark plugs, or supercharger efficiency loss, or high friction. This was the first time the engine throttle had been completely open and the 1,145 actual bhp output was very encouraging as the supercharger ratio was only 6:1; engine operation was very satisfactory.

The magneto points were changed once after a mercury manometer broke and spilled mercury on the magneto and rear cylinders. No further damage resulted. An external oil pressure line from the Cuno oil filter was installed on the cam boxes for more oil pressure. Testing was interrupted to inspect several cylinder head coolant leaks and a supercharger housing fuel leak. Inspection revealed the No. 3R piston scored on the thrust side and both oil control rings broken. The No. 5R piston had two deep scratches on the thrust side and all piston rings showed marks of some object passing the piston. The No 3R cylinder barrel was slightly scored. No leaks were found on any cylinder when tested under steam pressure. A small piece of copper-lead had flaked out of the right main thrust bearing. Both bearing halves showed heavy loading near the edges. In order to relieve the fit on the crankcase bearing cap side, the case sides were lapped to give 0.0015" clearance on the thrust bearing flanges. The supercharger housing leaks were caused by several studs pulling from the discharge housing outer rim and preventing a seal at the intake housing flange.

The engine was reassembled with a new No. 3R piston, pin and ring set and new piston rings for the No. 5R piston. The scored cylinders were lapped and stoned, and the supercharger housing studs replaced. Four spark plugs were replaced. After a 4:14 hr run-in on the 600 hp propeller load curve, the test was stopped due to low power at 2,900 rpm. Up to this point, engine operation had been nominal and compared with previous results. The engine did not turn freely by hand and when a cam housing cover was removed minute copper bearing material particles were found. The engine was completely disassembled and it was found that the Nos. 3 and 4 connecting rod bearings had failed. Bearing shell examination revealed that the bearing inner linings had failed; the outer lining was in good condition except for pitting caused by chips carried from the inner lining. The crankshaft was set up in the crankcase and oil flow checked throughout; it appeared an adequate oil supply had been maintained for all main and crankpin bearing journals.

XO-1430-1 Failed Nos. 3 and 4 Crankpin Bearings

P14 Fig. 1	P14 Fig. 2	P14 Fig. 3	P14 Fig. 4	P14 Fig. 5

The cause of this bearing failure was carefully investigated as these bearings were made from the same material that had previously given good service. The remaining bearing fits and clearances were closely examined and there was evidence that the oil film had been broken on more than one of the four remaining bearings. The only difference in this setup and the previous one was the increased connecting rod bearing crush. This materially stiffened the connecting rod and did not allow for as much deflection as with the previous setup. This lack of deflection may have restricted the oil flow. That the No. 3 connecting rod bearing was throwing a minimum of oil was evidenced by a No. 3 piston pin having slightly galled in the piston, and later a No. 3 cylinder had been scored. This bearing failure followed closely a similar bearing failure on the twin-cylinder test engine. Time run on the performance test engine was as follows:

Parts used, along with Government liability for the period, were attached. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 111 – 122.]

23 Jan 1940. In a meeting including Wild and Prescott, Kinnucan said that the twin-cylinder and XO-1430-1 No. 3 and 4 crankpin bearing failures had been studied in great detail. A change in bearing crush had been made prior to the failures. Tests made on the connecting rod with the crush amount formerly employed showed that the crankpin bearing went out of round about 0.0015" under load. This condition caused a considerable oil flow increase since a large clearance opening would be left in the unloaded bearing side, permitting oil to flow in excess of that expected from the previously established 0.003" clearance. No change in bearing clearance had been made when the connecting rod crush was increased, and this crush increase eliminated the connecting rod bearing deflection under load; this was believed responsible for the connecting rod failures. However, an undesirable feature of this increased crush appeared to be a reduction in oil flow through the bearing. On this basis the twin-cylinder bearing clearance was increased to 0.004" while retaining the previous bearing crush level. This bearing was being operated under severe test conditions in an attempt to establish the increased oil clearance as a remedy for the difficulty. Reduced oil flow evidence was also found in the No. 3 piston pin and No. 3 cylinder wall, which had suffered lubrication insufficiency. These failures had also occurred at about one-half engine load after the engine had successfully operated up to 1,200 hp without apparent bearing damage; failure at a light load might have been due to the fact that the bearing deflection was less than it had been at 1,200 hp. Prior to its failure the connecting rod bearings had not been examined for evidence of metal-to-metal operation. However, after the failure, other bearings that had not failed were found with bright areas indicating lack of an adequate oil film.

Kinnucan showed some rod bearings that had a thin copper plate on the outer portion where the forked rod clamped the bearing liner; these bearings showed less galling and metal pick-up than had been previously seen. Kinnucan said that the XO-1430-1 crankshaft had been cut and sprung to such an extent that it would be necessary to grind the Nos. 3 and 4 crankpins approximately 0.080" undersize, an operation that would nearly remove the crank cheek fillet and produce a weak area that would coincide with a torsional vibration node in close proximity. Kinnucan thought the crankshaft unfit for further service and recommended a new shaft when the engine was reassembled; Prescott agreed. Kinnucan had brought the failed crankpin bearings along with some good bearings for comparison. The failed bearings still had bronze on the outside even though the inside bronze was entirely missing. This was another indication of lubrication insufficiency.

Wild stated that the difficulties in preparing a contract on Project M-62-40 (the Continental XIV-1430-1) had been overcome in conference with the Contract section, and that a further conference with PPL Chief Maj Edwin R. Page had been arranged for Friday 26 Jan 1940. Wild and Kinnucan stated their desire to expedite work on this project to the fullest extent.

[USNARA RG342 P091053. 26 Jan 1940 Memorandum Report E-57-285-59, Crankpin Bearing Failures on the O-1430 Type Engines.]

26 Jan 1940. Haddad reported that CMC had decided to replace the O-1430-1 crankshaft, the Nos. 3 and 4 connecting rod sets, and a No. 5 cylinder that was leaking coolant from its head jacket. There was no plan to run this engine until twin-cylinder bearing test results became available.

The twin-cylinder engine was run-in for 5 hrs of which 2.5 hrs were under power to break in the new connecting rod bearing. Inspection revealed that the engine oil system had been insufficiently cleaned after the last failure and that lead-bronze flakes had scratched the crankpin and bearings. The oil system was again cleaned and the engine run for another 5 hrs, after which the crankpin and bearing were no worse. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 92.]

29 Jan 1940. Kinnucan and Wild visited Prescott at Wright Field and reported that the twin-cylinder test engine had completed approximately 20 hrs under severe conditions with the connecting rod bearing clearance increased to 0.004". After 25 hrs the bearing, cylinders and piston conditions suggested satisfactory oil flow. This was part of an effort to determine the best crankpin bearing clearance before the XO-1430-1 was reassembled for more performance testing. CMC estimated the XO-1430-1 would again be under test about 2 Feb 1940. The last monthly progress reports for this contract was to be sent on 31 Jan 1940; thereafter the reports would be furnished on a semi-monthly basis.

Kinnucan asked that the cylinder with bottom-seated spark plug gasket inserts be returned to CMC; this had been lent to MatCmd for use in high-output tests. The new-design cylinder head with more spark plug accessibility was being addressed by altering the present cylinder head pattern.

During a right-angle drive drawing review, Kinnucan stated that the ball-bearing manufacturer's recommendations had been followed but the outboard thrust bearing was 5 lb heavier than the present XO-1430-1 thrust bearing, which increased the bearing capacity only from 8,000 to 9,000 lb. The lighter bearing then in use was used almost entirely for engines in the power range covered by the XO-1430-1 design. Since the thrust was not affected by reducing the propeller speed, no reason existed for using the larger thrust bearing. The smaller, lighter thrust bearing would reduce right-angle gearbox weight by about 10 lb. The thrust bearings locating the bevel gears used split retainers, which were not clamped to prevent axial bearing motion. Prescott suggested a more conventional method be employed, such as one that incorporated bolts or studs to locate those bearings for either thrust direction in a manner similar to that almost universally used for propeller thrust bearings. The general right-angle drive design appeared almost ready for release. However, Kinnucan thought more coupling flange weight could be reduced. All these changes were to be incorporated in the final design,

The three men discussed the best way of prosecuting Project M-62-40 (the XIV-1430) in detail. Wild pointed out the necessity of having more than one engine in operation so as to expedite development to the fullest extent. CMC wanted to build four engines so that no delay would be introduced by parts failure during the 50-hr development tests. Representatives from the Chief Engineer's Office came to participate in the discussion and helped decide that only the first two engines would be fabricated; one would be delivered to MatCmd for the 50-hr development test and the second retained by CMC for additional testing at CMC's expense. The third engine would be fabricated with the first two and held as a spare in order the keep the first two in operation. At the 50-hr development test conclusion the third engine would be modified by CMC at CMC's expense to incorporate all changes found necessary during the 50-hr development test; also, at the same time, the fourth engine would be fabricated in accordance with changes dictated by the 50-hr development test as it was when it completed the testing. The Government would pay $50,000.00 to cover replacement parts used on the two engines during the Government- and CMC-conducted tests, and to place both engines in first-class operating condition in agreement with the final 50-hr development test engine, at the 50-hr development test conclusion. No obligation was to rest with MatCmd for modifying the third engine. In addition to these obligations, the Government would assume a $12,230.00 burden as covered by the CMC letter dated 7 Nov 1939, for incorporation of the offset gearing to bring the propeller shaft 9" below the crankshaft centerline. In all other respects, the price scheduled was to conform to the quotation contained on CMC's response to Request for Data R40-A, dated 11 Sep 1939. [USNARA RG342 P091041. 3 Feb 1940 Memorandum Report E-57-285-65, O-1430 and IV-1430 Engines.]

31 Jan 1940 Progress Report. No O-1430-1 running was done during this period. After the connecting rod bearing failure, a deep cut was found in the No. 3 crankpin fillet and the crankshaft itself had been badly overheated. CMC judged the crankshaft unsafe for continued operation and planned to install a new crankshaft from stock during the next assembly. Two cylinder assemblies were leaking at the cylinder jacket; these were from the original lot with chrome-plated lands on the jacket and CMC judged these leaks to be caused by the previously-experienced corrosive action. One cylinder also had a head crack. CMC expected to have the engine reassembled and running by 20 Feb 1940.

Time run under Contract W-535-AC-12594 was 76:50 hrs total, 12:19 hrs motoring, 64:31 hrs under power and 8:39 hrs above 160 bmep. Total engine time was 730:39 total, 188:11 motoring, 542.22 above 160 bmep, and 107:34 endurance under Contract W-535-AC-8131.

Twin-Cylinder Test Engine - Contract W-535-AC-12741: Inspection after the connecting rod bearing failure showed no serious damage except a badly scored crankpin and overheated connecting rod. The crankpin was reground undersize and a new connecting rod assembly was installed with a 0.004" clearance between the connecting rod bearing and crankpin, and a 0.0045" clearance between the connecting rod bearing outer shell and blade connecting rod. CMC thought a lack of oil clearance had contributed to the previous failure. After a 5 hr run-in to 3,000 rpm at 0 inHgG, the engine was disassembled and the connecting rod bearing examined. Very minute copper and bronze particles were in the oil and had slightly scratched the bearing. CMC thought these had been left in the oil system through the cleaning process. The engine was completely disassembled, all parts thoroughly washed, and the bearings accurately weighed in case any further bearing scuffing was suspected.

The engine was reassembled and 13:26 hrs time added before the next inspection. Of this 6:32 hrs was above 160 bmep to test the new connecting rod bearing's endurance. The actual cylinder compression ratios were checked; the right cylinder was 6.08:1 and the left was 6.12:1. The bearing condition was very good, but the steel back and forked connecting rod were slightly galled. The engine was reassembled and a mixture curve at 3,000 rpm and 4 inHgG run to check mixture distribution; the left cylinder tended to run leaner than the right.

The engine was assembled without change, four new spark plugs installed, and a Harrison oil cooler installed in the engine oil inlet line. Minor repairs were made to the tachometer and to the exhaust gas analyzer fittings on exhaust pipes. Engine running time was as follows:

Converting Wood Model – Contract W-535-AC-12298 – PO 39-2952: The wood model had been returned to CMC from Bolling Field. Some slight damage was done in transit, which was to be repaired before it was submitted for inspection on 15 Feb 1940.

XO-1430-3 Right-Angle Drive Engine – Contract W-535-AC-12594: Drawing checks were proceeding with slight design changes where necessary. The pinion and pinion shaft bearing preload method was revised. Torquemeter housing detail was still pending. Right-angle drive tubular mounting had been revised and detailed except for the method of locking the rubber biscuits in the mounts. Sectional assemblies were about 80% complete and a stock list was being typed. Cylinder head Dwg #505243 was released; this head incorporated angular spark plug locations to facilitate maintenance. No additional spare parts were used on the O-1430-1, but the attached sheets showed spare parts used on the twin-cylinder engine, together with Government liability. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 123 – 127.]

7 Feb 1940. Haddad reported a twin-cylinder run conforming to Contract W-535-AC-12741 Item 4 developed 185 bhp at 2,700 rpm and 24 inHgG, 194 bhp at 3,000 rpm and 24 inHgG, and 200 bhp at 3,300 rpm and 24 inHgG. Oil-in and coolant-out temperatures were as much as 5°F below the contract limit and the coolant flow was as much as 4 gpm above the contract limit. No effort was made to obtain the maximum pressure called for in the Item.

The twin-cylinder was run from 3,300 to 3,600 rpm in 100 rpm increments at 0 inHgG. Airflow increased up to 3,500 rpm and dropped at 3,600 rpm; the power also dropped off. This seemed to indicate a volumetric efficiency loss at the higher speed. On tear-down it was found that the valve spring tips were broken. A third spring intended for the original engine, was added to overcome this difficulty. The 6.0:1 compression ratio pistons were measured; actual compression ratios were 6.08:1 on the right and 6.12:1 on the left. The 7.5:1 pistons were found to have 7.18:1 on the right and 7.17:1 on the left.

The 7.5:1 compression ratio pistons were installed and run-in for 2.5 hrs motoring and 5 hrs under power. Total time on the twin was about 99 hrs or which about 67 were under power. The forked rod that was in the engine during the 5 January failure was being used and the forked rod it replaced was to be reground to take a copper-plated bearing in place of the original bearing.

[USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 93 – 94.]

15 Feb 1940 Progress Report. No XO-1430-1 running under Contract W-535-AC-12741 occurred during this period. Replacement part machining was nearing completion. Total engine run time on the contract and total time overall was unchanged from the 31 Jan 1940 Progress Report.

Twin-Cylinder Test Engine – Contract W-535-AC-12741: power versus boost pressure runs were made at 3,000 and 2,700 rpm with readings from 0 to 24 inHgG in 4 inHgG increments. Friction readings were taken for each corresponding boost interval. The mixture distribution was not satisfactory during these runs, with the left cylinder running considerably leaner than the right. Attempts were made to run at 3,600 rpm, but it was evident that the power output was low. An airflow versus rpm curve at 0 inHgG indicated that the valve gear was not functioning normally above 3,550 rpm. The engine was disassembled for inspection, to install additional valve springs, and to install the higher-compression piston called for in Contract Item 5.

Both exhaust valves showed slight ridges on their faces and two reconditioned valves were installed. The right intake valve spring lower retainer had its flange cut off by a ragged edge on the valve spring, which had been broken off at the tip end. The forked connecting rod was slightly galled on both the cap and rod end; this rod bearing was not the type with the copper plating on the back. Coolant flow manometers were recalibrated and the engine reassembled for running. After a 7-hr run-in up to 4 inHgG at 3,000 rpm an examination showed the new pistons in very good condition. A clearance volume check disclosed that the compression ratio was 7.22:1

P14 Curve 112

The twin-cylinder running results had not been satisfactory; a careful investigation was made to find the cause for low power output. A Stromberg type NA-U8G double-barrel carburetor was installed with one barrel plugged off. Mixture ratio curves were run and a very decided power output improvement observed. Based on imep readings, the engine produced 25% more power at 12 inHgG and 3,000 rpm.

A Moto-Vita analyzer was set up in conjunction with the Breeze exhaust analyzer unit in order to correlate mixture distribution indications, as it was felt that the Breeze instrument readings were not accurate. A manometer was installed to give differential pressure at the right and left cylinder head intake elbows. Compression and differential pressures were recorded at 0, 4, and I inHgG and at 2,700, 3,000 and 3,300 rpm as shown on Curve 112, which exhibits 18% higher pressure in the left cylinder. The intake pipes were removed and differential pressures determined at both cylinder elbows; the maximum differential pressure was 1 inH₂O for the left cylinder, which indicated that the cylinders were giving equal performance, but the manifold was causing the surge and poor mixture distribution. The test setup was altered so that the carburetor used both barrels. A new intake pipe was made with each branch connected to a carburetor throat. Compression and differential pressure tests showed very uniform mixture distribution. Mixture ratio curves at 0, 4, 8 and 12 inHgG at 3,000 rpm were run. The fuel/air ratio was in close agreement for both cylinders and the power output at 12 inHgG was 256 imep at 3,000 rpm with the 7.2:1 compression ratio pistons.

Running time was as follows:

Converting Wood Model – Contract W-535-AC-12298 – PO 39-3952: The wood model was unpacked at Detroit after its return after its return from the Air Corps Demonstration at Bolling Field; slight damage had occurred in transit. CMC was repairing the damage and expected this to be completed by 21 February, at which time the model would be submitted to the Air Corps Inspector for acceptance.

XO-1430-3 Right-Angle Drive Engine – Contract W-535-AC-12594: Right-angle drive unit pinion shaft damper details were pending final damper data before proceeding with checking. Right-angle drive housings were being checked and would be ready for corrections in a few days. Reduction gear shaft, pinion shaft, pinion gear shaft and bearings were being checked in conjunction with housings. Bevel gears had been released. The right-angle drive engine front end details, consisting mainly of the new nose housing, drive shaft and bearings, were expected to be ready for release by 23 February. Sectional assemblies were complete except for minor additions pending remaining detail releases. A cylinder jacket layout with a separate coolant flange, hydrogen-brazed to the jacket instead of the present method of machining completely from a single stock piece, had been made.

XIV-1430-1 Inverted V-12: Engine front end layouts incorporating reduction gears, starter, generator drives, propeller governor drive and scavenge systems had been started. Proposed installation drawings had also been made; these were in addition to preliminary layouts already submitted.

Inverted V-2 Cylinder Test Engine: Preliminary arrangement layouts had been made and were ready for discussion before proceeding to final layouts. No additional spare parts were used on the XO-1430 engines during this period. However, the attached sheets showed spare parts used on the V-2 engine, together with total Government liability. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 128 – 134.]

15 Feb 1940. Prescott originated a hand-written Authority for Purchase to reimburse CMC for parts used in testing from 15 May 1939 to 15 Feb 1940. Interestingly, the last page has Project M-62-40 (XIV-1430) engine specifications. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 218 – 222.]

23 Feb 1940. Haddad reported that since the 15 Feb 1940 Progress Report that the twin-cylinder test engine had developed a coolant leak around the cylinder head core plug. This had to be repaired and the engine had only been run for about 8:30 hrs, 6 of which were under power. These runs did not develop the same power for a given boost that previous runs had. CMC was trying to find the reason. CMC thought that the Contract Item 4 runs described by Haddad in his 7 Feb 1940 report could be improved with a new carburetor and manifold setup; they were to be repeated. However, if CMC decided to submit the original runs it would have to apply for a deviation to the Item 4 requirements. CMC had requested an official deviation on measuring maximum pressure by the balanced valve method called for by Item 4.

The XO-1430-1 was awaiting three cylinder assemblies to replace ones with coolant leaks. Some subassemblies had been completed, and the connecting rods and bearings were being checked. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 135.]

26-27 Feb 1940. Prescott visited CMC to review the inverted V-twin test engine, part of the XIV-1430 development, whose layout was nearly complete and whose detail drawings covering the engine balancing would be in preparation in the next 10 days. This engine crankcase, like the XIV-1430-1 engine it represented, was a welded-composite construction and would incorporate the same crankshaft as used in the opposed twin-cylinder test engine. The IV-twin balancing had been solved in a very simple manner by rotating weights as used in the opposed twin-cylinder engine.

XIV-1430 Installation Drawings		XIV-1430-1 and -3 Accessory Section

A fairly complete quarter-size XIV-1430-1 installation drawing was reviewed and one-tenth scale Photostat installation drawings were furnished to MatCmd. The engine front-end layout included a pair of spur gears to offset the propeller centerline 9" below the crankshaft centerline in the approximate center of a circumscribed circle. The spur gear pair rotated the propeller shaft in the opposite direction to the crankshaft, causing the reduction gear housing to be subjected to the sum of the propeller and engine torques. This would require a very complete stress and deflection analysis before deciding how to resolve this torque to the airplane structure, ideally without it being transmitted through the crankcase. However, it was not yet known what problems the nacelle design would have to address to provide for torque reaction at the engine forward end. This matter was to be thoroughly investigated before any XIV-1430-1 crankcase drawings were released.

CMC and Prescott studied supercharging the XIV-1430-1 and controlling its superchargers in considerable detail. CMC had requested from General Electric Company (GE) a turbosupercharging analysis, and GE had supplied a 1935 report with a statement that the report's data had not been revised to include later information and was believed by GD to be sufficient for turbosupercharger application to this engine. The first XIV-1430-1 engine design would obviously be around this turbosupercharging application. However, alternative supercharging methods using two-stage geared superchargers with intercooling were also discussed. CMC was to prepare an analysis and submit a proposal to MatCmd as early as practicable, but the analysis was not to interfere with prosecution of the turbosupercharged XIV-1430-1.

Kinnucan requested information on how to handle classified data associated with Project M-62-40. It was his understanding that all such data was kept locked in a safe at MatCmd but no specific instructions had been issued to CMC covering the required methods of handling such data in the CMC plant. MatCmd requested that a safe be provided to safeguard all such M-62-40 information, and suggested that full information as to Army Regulations No. 380-5, covering the handling of restricted projects, be obtained by CMC from the Government Printing Office so as to protect CMC against liability under penalties imposed by the Government for mishandling restricted project information. MatCmd's Contract Section Chief would be able to provide additional information during CMC's next visit to Wright Field. [USNARA RG342 P09998. 1 Mar 1940 Memorandum Report E-57-285-83, XIV-1430-1 Engine.]

26 – 27 Feb 1940. During Prescott's CMC visit he witnessed the twin-cylinder test engine in operation using a two-barrel pressure carburetor that appeared essential to smooth operation of the twin-cylinder opposed engine with 180° and 540° crankshaft firing events. Considerable difficulty had been encountered because of this when using a single-barrel carburetor in common with both manifold ducts. Now the twin-cylinder engine operation was exceptionally smooth but the performance was slightly inferior to what was expected. CMC was continuing to study this and stated that if the two-barrel carburetor improved engine operation sufficiently the first test series, in which the coolant flow and outlet temperature were slightly outside the contract requirements, would be discounted and the performance determined under better operating conditions. The Farnborough indicator was being installed to take indicator cards in the manifold duct in an effort to discover a reason for the engine's inferior performance. The 7.0:1 pistons had been installed but it appeared that detonation would prevent meeting contract requirements for boost pressures up to 26 inHgA. Prescott suggested that CMC request MatCmd to permit the use of Power Plant Fuel No. 628 for all runs above the detonation point on 100 PN fuel. It was obvious that when 8.5:1 piston were installed it would be impossible to carry the engine output much above 4 – 6 inHgG. Prescott suggested that the mixture control setting be kept as lean as permitted by detonation or other considerations, except where the output was sufficiently high to substantiate mixture enrichment to suppress detonation. Kinnucan asked if it would be permissible to carry the engine output above that corresponding to 26 inHgG and secure indicator cards under these conditions. Prescott thought such tests should be deferred until the specific requirement covered by the contract were completed, at which time a request addressed to the Chief, Experimental Engineering Section, for permission to continue the testing to higher outputs. It was obvious that both CMC and the Government would both profit by any additional data that might be obtained in this manner.

CMC had made a few minor changes to the XO-1430-3 front end that would improve the final design; a further change was discussed in which a spur and bevel gear setup was connected for driving the propeller governor and pump. This change would make the driving gear backlash independent of the end-wise propeller shaft motion. The right-angle and reduction gear drive layout was found to be in nearly final form for release. A few minor changes were being made, including lightening the coupling shaft between the engine and gearbox and the gearbox and propeller. The gearbox couplings at both engine coupling shaft ends and at the propeller coupling shaft rear were slightly reduced in size to correspond with the gearbox coupling loading that had been used during all tests to date on the engine quill shaft rear end. Final modification to the large thrust bearing retainers taking the right-angle drive bevel gear thrust was discussed. The same change in the governor drive mechanism to incorporate a spur gear contact with the propeller shaft was to be incorporated in this unit.

The latest rear accessory section layout to be used with future O-1430 type engines was examined. The gear train was considerably simplified and the new coolant pump location on the engine left side and oil pump on the right side was far superior to the previous layout. An auxiliary pressure system was installed so that oil was bled off the main oil gallery through an orifice, permitting a limited oil flow to the rear section; this oil pressure was regulated via a low-pressure relief valve.

When Kinnucan was asked when the XO-1430-3 drawings and specifications would be submitted for release, he thought these would be ready around 8 Mar 1940, at which time he would submit both drawings and specifications with a request for official release. [USNARA RG342 P090995. 1 Mar 1940 Memorandum Report E-57-285-84, XO-1430-3 Engine and Twin Cylinder Test Engine.]

29 Feb 1940 Progress Report. No XO-1430-1 running was accomplished during this period. Thus, cumulative times remain the same as those reported in the 15 Jan 1940 Progress Report. Three new Dwg #503632 cylinder assemblies were being fabricated. Meanwhile the reduction gear, rear accessory housing, other cylinders, and valve gear had been inspected and assembled. The new crankshaft was assembled with new journal plugs and sleeves. Crankpin and main journal diameters, along with blade rod diameters and forked connecting rod bearing diameters were measured and recorded. The engine was expected to be assembled and ready to run on 11 Mar 1940.

Twin-Cylinder Test Engine – Contract W-535-AC-12741: The cylinders and valve gear had been disassembled for inspection and found in good condition. Trouble had been experienced with coolant leaks from the cylinder head core plugs. The pipe plugs were drilled out and the cylinder head threads examined and found in good condition. CMC thought the coolant leak might be coming from the vee thread apexes, following a spiral path and emerging at the top. CMC decided to eliminate the pipe plug and use a shouldered plug with a gasket to ensure a sealed coolant system. Mixture curves were run, but the power was lower than expected. The Dynamometer was recalibrated to eliminate a possible error source.

A power versus air intake temperature run was made at 2,700 rpm and 4 inHgG while warming up. Then the power curve at 2,700 rpm and 4, 8, 12, 14, 16, 18 and 20 inHgG using 200°F to 210°F air intake temperature was completed; power peaked at 20 inHgG and detonation was too severe to continue. Friction values at the corresponding boost values were also determined. Trouble was again experienced with the Breeze exhaust gas temperature analyzer. In order to check its operation the right and left intake tubes were interchanged and a power curve at 3,000 rpm and 0 to 24 inHgG was run. The Farnborough indicator was set up and several cards were taken, but they were not satisfactory due to trouble with the indicator valve. New indicator valves were to be installed and the cards taken again. Both Champion RJ-11 and Bendix 300 P.D. spark plugs continued to give serious trouble.

A power curve at 3,000 rpm and 0 to 24 inHgG was taken under Contract Item 5 conditions using spark advance and mixture settings previously determined from mixture ratio curves. The fuel settings were on the rich side of best power. A friction run at 3,000 rpm and 0 to 24 inHgG was also run. The power curve at 3,000 rpm was repeated to obtain better specific fuel consumption at 0, 4, and 8 inHgG; the test was twice interrupted to repair a broken left cylinder exhaust pipe. Curve No. 120 shows power output versus carburetor air pressure at 3,000 rpm. Another power output versus carburetor air pressure curve was completed up to 18 inHgG; no friction runs were taken. Twin cylinder running time as of this date was as follows:

Converting Wood Model – Contract W-535-AC-12594 – PO 39-3952: The XO-1430-3 wood model was completed, accepted by the Air Corps Inspector and shipped to Wright Field on 20 Feb 1940.

XO-1430-3 Right-Angle Drive Engine – Contract W-535-AC-12594: All new engine nose housing, accessory case and drive, coolant pump and coolant manifold detail drawings had been released. Drive shaft and associated parts were checked and ready for release. Right-angle drive housing drawings were being corrected and will be released when the final check was complete. The reduction gear shaft was partially checked with release pending a decision on propeller governor drive from this shaft. Pinion, pinion gear shaft and associated parts were to be released as soon as checking was complete. Damper parts on the pinion shaft, the torque meter housing and related parts were held up pending further calculation checks.

Project M-62-40 (XIV-1430-1): Covered under a separate report.

XO-1430-1 Spare Parts: Injection carburetor installation layouts were made based on Bendix Model PD-12-B6 with the injection nozzle integral with the supercharger attaching elbow. No additional spare parts were used on the XO-1430-1 during his period, nor were any twin-cylinder spares used. A Government liability statement was attached. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 187 – 192.]

2 Mar 1940. Haddad reported that after running for a short time the twin-cylinder engine was disassembled and the left piston and cylinder were found burnt near the exhaust port. The left and right piston/cylinder assemblies were interchanged to see if detonation would follow the cylinder or if the setup was faulty. Mixture runs were made at 4, 8, and 12 inHgG, followed by Contract Item 5 runs a 2,700 and 3,000 rpm and from 0 to 24 inHgG boost. When runs were attempted at 3,300 rpm a decided power drop was noticed at 4 inHgG. On inspection, the forked rod was found fractured starting at the connecting rod bolt head countersink head fillet. The connecting rod bearing had started to fail and was severely scored. The crankpin was also scratched. This same forked rod was the one that failed on 5 Jan 1940. It was returned to the engine on 5 Feb 1940, and it was likely that the current failure was traceable to the 5 January failure when the rod overheated. The XO-1430-1 was still awaiting three cylinder assemblies. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 136.]

11 Mar 1940. Wild visited Prescott at Wright Field and requested information about how MatCmd provided an indicator opening in a standard O-1430 cylinder. This method of tapping the cylinder was described in a sketch that described installing a maximum pressure indicator of the balanced-pressure type, as specified by the Contract. Work was in progress on the twin-cylinder engine but the cause of unequal cylinder performance had not been determined. Prescott suggested that by operating on one cylinder by cutting out the opposite cylinder might help determine the correct mixture control setting without referring to exhaust gas temperature indicator.

All material for assembling the XO-1430-1 was to be on hand by 12 March, at which time the engine would be assembled and tests resumed. Provisions had been made at both CMC Detroit locations (where the CMC Engineering Department still worked) to lock up all documents dealing with restricted projects and that all due precautions would be exercised to ensure that such documents were handled in accordance with Government regulations. Wild stated that all XO-1430-3 part layouts were practically complete and that work on projects other than for MatCmd were being closed out as rapidly as possible in order to permit the Engineering Department to give undivided attention to Air Corps projects. [USNARA RG342 P090996. 14 Mar 1940 Memorandum Report E-57-285-97, O-1430 Type Engines.]

15 Mar 1940 Progress Report. (Note: This report's first page is missing, so we begin by discussing the twin-cylinder last run.) The engine was run up 3,300 rpm and 4 inHgG boost to check power, which was satisfactory. It was then disassembled for connecting rod and bearing inspections, which were found in good condition. The engine was reassembled in preparation for continued official running. Engine time to date was as follows:

XO-1430-3 Right-Angle Drive Engine – Contract W-535-AC-12594: All new engine detail drawings and parts identical with the XO-1430-1 had been released to the shop. The right-angle drive and reduction gear unit was completely detailed and partially released. The remaining drawings were to be checked shortly. The long-lead-time parts had been released so that the remaining parts would not prolong the final completion date.

XO-1430-1 Spare Parts: Layout on an injection carburetor with injection nozzle in the supercharger elbow had been completed. Tubular engine mounts with rubber biscuits were detailed and checked, and were to be released at once. No additional spares were used on the XO-1430-1 during this period. However, the attached sheets showed spare parts used on the twin-cylinder engine, together with Government liability. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 183 – 186.]

22 Mar 1940. Haddad reported that the twin-cylinder engine was run at 3,300 rpm from o to 24 inHgG in accordance with Contract W-535-AC-12741 Item 5, but the maximum combustion chamber pressure was not taken. The XO-1430-1 No. 5L cylinder, which had a crack in the head coolant jacket, was repair and an insert placed in the head to take the valve for measuring maximum pressure. After this cylinder was run-in, runs were made at 2,700, 3,000 and 3,300 rpm and 0, 8, 16 and 24 inHgG and the maximum pressure recorded for each point. A 3,600 rpm run was then made from 0 to 24 inHgG in accordance with Contract Item 5 and the maximum pressure recorded. The Item 5 maximum pressure had not yet been taken at 4, 12, 15, 18, 20 and 22 inHgG boost at 2,700, 3,000 and 3,300 rpm. The XO-1430-1 was still awaiting three cylinder assemblies and a new forked rod. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 193.]

22 – 23 Mar 1940. Kinnucan met with Prescott and announced that the XO-1430-3 drawings would be ready within the next few days and would be forwarded to MatCmd with the request for official release. These drawings had been studied in detail by various MatCmd personnel; some that could be released by CMC were already being fabricated and the others would enter fabrication as soon as the drawings were released.

Four new cylinder assemblies had been built in Muskegon, but due to a misunderstanding by Inspection personnel were thought to have been incorrectly ground. He stated that it was impossible to check these after removal from the grinding machine since the barrels were straight and round only when elevated to operating temperature. The grinding machine was equipped with a hot oil circulating system so that the cylinders were heated to 265°F during the grinding process; when the cylinders were removed and cooled they were distorted. This grinding method evolved during early unsatisfactory development experience where piston ring life was drastically shortened when running in cylinders that were ground straight and true when cold. Prescott suggested that CMC request that these four cylinders be accepted on the basis of CMC's guarantee that they would be up to the required performance standards.

Kinnucan said that CMC had encountered considerable difficulty with the maximum pressure measurement called for in Contract W-535-AC-12741. The indicator valve had not worked reliably when used with the Farnborough-type indicator. Prescott suggested using the NACA maximum pressure indicator that used a small diaphragm and made electrical contact on only one side. No leakage could occur with this diaphragm and measurements were claimed to be reliable. [USNARA RG342 P121274. 26 Mar 1940 Memorandum Report E-57-285-105, Conference with Representative of Continental Motors Corp. on the XO-1430-3 Engine, and XO-1430-1 Engine Test.]

28 Mar 1940. XO-1430-1 development, including all single-cylinder development, building and testing the 12-cylinder engine, and replacement parts used during this engine's testing through the 50-hr development test, amounted to $259,224.64. In addition, twin- and 12-cylinder tests were in progress with a view to improving the military utility of these engines by increasing their ratings. These tests were to include an unknown quantity of replacement parts. The amount obligated for the tests alone was $35,646.00. This made a $294,870.64 total plus the necessary replacement parts used during the tests. The XO-1430-3 engine and development test called for a $71,507.00 expenditure. This development included a new right-angle drive and extension shaft arrangement to enable the engine to be installed within the wing root and the propeller installed at a thinner outboard wing section. This development also called for an unknown replacement part quantity. Total funds obligated to cover these two developments was $366,377.64 with the possibility that replacement parts might raise the figure to around $400,000.00. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 28 Mar 1940 Memorandum Report EXP-M-57-503-106, O-1430 Type Engines – Development Costs. 196]

29 Mar 1940. The twin-cylinder 7.2:1 compression ratio pistons were replaced by 6.1:1 pistons. Contract Item 4 runs were made at 2,700, 3,000 and 3,300 rpm from 0 to 24 inHgG boost. Maximum pressure at 3,300 rpm appeared to be too high and were to be rechecked. When 3,600 rpm runs were attempted the beam load suddenly dropped; teardown revealed the crankpin bearing and crankshaft rear bearing had failed. XO-1430-1 reassembly had started using two new cylinders and the one removed from the twin-cylinder engine when the XO-1430-1 No. 5L cylinder was installed. The new forked rod being to be used on the No. 3 crankpin was rejected by the Air Corps Inspector because the crankpin bearing lip dimension was not within limits. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 197.]

1 Apr 1940. In a telephone call including Kinnucan, Air Corps Inspector Walter A. Ryan, MatCmd civilian engineer N.W. Lake and Prescott, Kinnucan asked whether an available forked connecting rod should be used in assembling the O-1430-1 for continuing the tests under Contract W-535-AC-12741. This connecting rod was under-dimensioned on the distance between the counterbores at either crankpin bearing end and the rod would not fit tightly into the corresponding crankpin bearing grooves by 0.005" to 0.006". He stated that this connecting rod was placed in a testing machine on an arbor and loaded by a testing mechanism and that no forked-end spreading could be observed. MatCmd asked what delay would be caused by installing a new rod instead; Kinnucan stated that a new rod could be obtained by 10 April. Lake opined that the present rod should not be used since this rod's loss would undoubtedly wreck the O-1430-1 and end testing for a considerable period. It was decided that the present rod would be set aside and that a new rod would be expedited. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 4 Apr 1940 Memorandum Report EXP-M-57-503-115, O-1430-1 Engine. 198 – 199.]

6 Apr 1940. Haddad reported that the twin-cylinder engine blade rod was cracked from the bolt hole to the outer edge at the parting line after the 28 Mar 1940 failure. The engine was reassembled using the blade rod from the engine that had failed on 5 Jan 1940 and new SKF main ball bearings instead of the roller bearings formerly used. A new rod bearing was also installed. The engine was run-in for 5:15 hrs from 500 to 2,700 rpm when the front main bearing suddenly failed on 5 Apr 1940. The forked rod installed on the XO-1430-1 No. 3 crankpin was not accepted by the Air Corps Inspector and was removed from the engine. No further work had been done on this engine as it was awaiting a new forked rod. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 200.]

12 Apr 1940. Haddad reported that the twin-cylinder crankcase and crankshaft had been checked for alignment; while the crankcase checked OK the crankshaft was bowed about 0.006". After straightening the crankshaft, the engine was reassembled with two new ball main bearings. On 11 April, the engine was run-in for 2:11 hrs from 500 to 1,700 rpm; on 12 April the engine was run for 23 minutes up to 2,400 rpm when it suddenly seized. The front main ball bearing had failed after 2:24 hrs total time. CMC thought the last two failures were set-up problems and not problems with the parts themselves. The XO-1430-1 was still awaiting the forked rod. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 201.]

17 Apr 1940. Haddad reported that the twin-cylinder engine bearing retainers were machined to give 0.0005" clearance as the previous failures were thought due to pinch on the balls caused by the bearings being press-fitted into the retainers. The engine was assembled using new main ball bearings. After a 1:40-hr run-in a run was made at 3,300 rpm and 0 inHgG to check a previous run's maximum pressure values. The boost was raised to 8 inHgG and while spark advance and mixture adjustments were being made the torque beam began to drop. Friction at 3,000 rpm was high, so the engine was torn down to reveal a failed rod bearing. The XO-1430-1 had been reassembled and was being run-in. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 202.]

A second oil hole was drilled in the twin-cylinder crankpin 180° from the first and piston oil squirt orifices were also installed. A new rod bearing with its parting edge beveled was installed in the forked rod. The bearing was run-in for 4:33 hrs to 3,000 rpm and 0 inHgG. The bearing appeared to be in good condition upon inspection. A second run of 5:13 hrs had low power and high friction. The left intake rocker roller and cam were found to be severely scored as in the failure of 26 Dec 1939; the cam oil hole had become plugged. A further run of 35 minutes after replacing the cam and roller showed friction still high. A complete tear-down revealed the rod bearing had failed.

The XO-1430-1 was run for 5:03 hrs up to 3,000 rpm and 600 hp; teardown revealed hard wear on the connecting rod bearings. Engine reassembly was awaiting results from the twin-cylinder rod bearing tests. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 203.]

6 May 1940. Prescott visited CMC where Kinnucan stated that the XO-1430-3 specifications were ready to be mailed to MatCmd for release. The right-angle gearbox, connecting shafts, and propeller thrust bearing and support total weight was 436 lb; the reduction gear and case that had been removed from the engine was 220 lb. This left an estimated 216 lb weight increase on account of the right-angle drive and extension shafts, bringing the total estimated XO-1430-3 weight to 1,486 lb. This value, however, was subject to revision if changes identified during the testing program were made.

Kinnucan said that the next item to be completed on the twin-cylinder testing program was Contract W-535-AC-12741 Item 4. This was to be done with 6.5:1 compression ratio pistons instead of the 6.0:1 pistons specified by the Contract. Prescott suggested the CMC submit a letter to MatCmd requesting this and other changes that appeared desirable.

The twin-cylinder test engine was examined to explain the connecting rod failures that had occurred with this engine. Prescott observed that oil was fed into the crankshaft from one end only and that an oil bleed was installed at the other end to provide for lubricating the main ball bearings. MatCmd had observed that it was necessary to feed oil to the crankpin from both crankshaft ends in high-speed engines. Kinnucan suggested an intermediate step in which the oil passage to the crankshaft would be enlarged and the crankshaft oil bleed plugged. Main ball bearing lubrication would be accomplished by an auxiliary oil jet connected independently to the engine pressure system.

Kinnucan observed that the twin-cylinder crankshaft was softer than was desirable for use with copper-lead bearings. CMC had considered the use of Tocco-hardened crankpins so as to increase the crankpin journal life. The Tocco hardening process used alternating current magnetic fields to heat the surface of parts, followed by rapid quenching. However, CMC had discovered that Tocco-hardened crankshafts after being ground, did not remain straight. Consequently, CMC was seeking other means to overcome the bearing trouble before resorting to hardened crankshafts. These alternative approaches included impregnating the bearing material with oil followed by lead plating, thereby producing a softer surface in contact with the crankshaft. CMC also had discovered that high-speed racing automobile engines had not successfully used copper-lead bearings, but were using very thin Babbitt metal in the connecting rod lower ends without bearing shells. While the bearing shell could not be eliminated for the forked-and-blade connecting rods, other bearing materials, such as cadmium silver, might be available for testing.

Kinnucan asked for data in the water brake and scales that MatCmd had available for use in connection with an accelerated twin-cylinder testing program. Prescott stated these would be forwarded to CMC. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 11 May 1940 Memorandum Report EXP-M-57-503-127, Visit of Mr. F.L. Prescott to Continental Motors Corporation Regarding the XO-1430-3 Engine and Twin Cylinder Tests. 205 – 206.]

11 May 1940. Haddad reported that the twin-cylinder engine was run at 3,300 rpm on 8 May and at 3,600 rpm from 0 to 14 inHgG on 9 May. A run at 3,600 rpm at 16 inHgG on 10 May was followed by one at 18 inHgG boost, but the engine failed. Teardown inspection revealed the right piston was smashed to bits, the right piston pin broken, the left piston broken, both cylinder barrels torn at their bottoms, both connecting rods broken and the crankpin bearing wound around itself. The crankshaft and primary balance shafts were also severely damaged.

The XO-1430-1 crankshaft had been reground and lapped to produce and extremely smooth crankpin finish. New bearings were to be installed. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 204.]

13 May 1940. Continental Aviation & Engineering Corporation (CAE) took over work on the XO-1430 and XIV-1430.

6 Jun 1940. CAE engineers Aland, Carl Bachle and Kalb visited MatCmd to examine a Rolls-Royce Merlin engine. They seemed most interested in the pistons, connecting rods, main bearings and crankshaft. It was not possible to examine the crankshaft main bearing lubrication but the main bearings were examined and MatCmd personnel explained that all connecting rod bearings were fed from main bearings Nos. 3 and 5 aided by main bearing Nos. 2 and 6. Main bearing Nos. 1, 4 and 7 had no features for lubricating crankpins. Supercharger drive details were examined and the reduction gear components were measured. The examination was not with a view toward manufacturing the Rolls-Royce engine, but with a view to improve the CAE engines being fabricated for the Air Corps. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 11 Jun 1940 Memorandum Report EXP-M-57-503-151, Examination of Rolls-Royce Engine. 207.]

20 Jun 1940. Haddad reported that the XO-1430-1 had been run in for 5:34 hrs on the 600 hp propeller load curve to 3,000 rpm. Tear-down inspection revealed the lead coating on the bearings was scratched and slightly worn but in good enough condition to continue. The worn supercharger oil slinger was replaced, along with a roller bearing and a ball bearing. A mixture curve at 8 inHgG and 3,000 rpm was run with the old Dwg #503797 manifold and then repeated with the new flat Dwg #500919. The new manifold showed a very slight power increase in this condition. A mixture curve at 8 inHgG and 3,000 rpm with a pressure carburetor showed very little difference, but at full throttle the fuel consumption was higher and the engine did not run as well as with the old carburetor.

At 2,200 rpm the power fluctuated so much at full throttle that no readings were taken. Runs at 3,000 were attempted and at 4 inHgG as the mixture was being leaned, the engine backfired and was stopped. Inspection showed that the key in the spur gear driving the right camshaft was missing and the nut and washer had dropped off. Retainers on the two ball bearings on the reduction gear spider gears were broken.

The twin-cylinder engine had been reassembled with a new crankshaft, new connecting rods, rod bearings, pistons, pins and rings. One new cylinder was installed and the XO-1430-1 6L cylinder removed on 29 May due to a crack in the head jacket; this cylinder had an insert placed in the head for a maximum pressure indicator. The engine was run-in for 6:55 hrs, torn down, and the lead coating found scratched and slightly worn as in the XO-1430-1 bearings. The engine was reassembled and run at 3,000 rpm from 0 to 16 inHgG. Power was slightly lower than on pervious runs. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 208 – 209.]

21 Jun 1940. Haddad reported that the XO-1430-1 right camshaft driving spur gear key had not yet been found. Since the keyway was undamaged, the key was thought to have come out with breaking. The cotter pin locking the gear was broken. There was no apparent damage except this and the ball bearing retainers previously mentioned. The twin-cylinder engine was run at 3,600 rpm for a Contract Item 4 attempt at 0 and 4 inHgG. When the boost was raised to 8 inHgG the torque beam began to drop, as did the oil pressure; oil-out temperature went up. A tear-down inspection sowed the lead-coated connecting rod bearing that had been in good shape during the previous inspection had failed; the crankshaft was slightly scored, but other parts seemed unaffected. These new parts had a 14:34-hr total time of which 9:21 hrs was under power. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 210.]

10 Jul 1940. CAE's Mr. Dreyer met with MatCmd's Newman and Prescott to discuss CAE XO-1430-3 Specification No. 1002-A, dated 10 Jun 1940, in great detail. Newman informed Dreyer that an engine installation drawing was a necessary specification component. The parties agreed that the specification would be corrected or revised to reflect the decisions arising from their meeting and that the revised specification would be submitted to MatCmd expeditiously in order to avoid further delay in a formal release. [USNARA RG342 P120973. 9 Jul 1940 Memorandum Report E-57-285-161, Telephone conversation & conference with representative of Continental Aviation & Engr. Corp., on XO-1430-3 Specification.]

11 Jul 1940. Haddad reported that the XO-1430-1 had not been reassembled since its 19 June failure. The reduction gear pinion bearings were found tapered and were replaced. The pinion thrust ball bearings were also replaced. Five of the seven main bearings were cadmium plated on their backs to increase bearing crush. The No. 3 forked rod was stoned to remove gall marks, and since this was now oversize, a new rod and bearing were to be used.

The twin-cylinder crankshaft, which was bowed after the 20 June failure, was straightened. The forked rod piston pin bearing was found not parallel with the crankpin bearing and was replaced. A rod bearing taken from the XO-1430-1 on 18 April was machined and Bermax (a high-lead Babbitt) coated. The blade rod bearing coating peeled but was considered good enough to be used. The carburetor venturis were changed from 2-1/2" to 1-3/8" to increase mixture control range and improve mixture distribution, but after running the 2-1/2" venturis were reinstalled. The engine was reassembled with 8.5:1 compression ratio pistons and run-in 6:01 hrs motoring and 4:53 hrs under power. On tear-down inspection the rod bearing was in like-new condition. A run was made at 2,700 rpm from 0 to 16 inHgG. A check run was later made at 0, 4 and 8 inHgG, but when 12 inHgG was tried the rod bearing failed because its Bermax coating had peeled off; interestingly, the blade bearing had not peeled any more than before it was assembled. Apparently the bond between the copper-lead and Bermax was not very good. Total time on this bearing was 5:34 hrs motoring and 8:35 hrs under power. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 211.]

28 Jul 1940. Haddad reported that the XO-1430-1 had been reassembled with a new forked rod and bearing on the No. 3 crankpin. A Moto-Vita was connected to each cylinder exhaust and on a 6-hr run-in to 3,000 rpm and 4 inHgG boost, the distribution was found to be fairly even. The Moto-Vita was an indicator that when connected to the exhaust pipe registered how much gas the engine generated; it was originally intended to help tune engines for maximum efficiency and minimum carbon monoxide. The reduction gear was mistakenly assembled to a 1.82:1 instead of 2.218:1 ratio. Tear-down inspection showed a one of the new reduction gear retainers was broken. Reassembly was started.

An oil feed to the twin-cylinder crankshaft front end was installed; this engine also run with the Moto-Vita to check distribution. After a 5:17 hr run-in the engine was inspected. The forked rod that had been taken from the XO-1430-1and new lead-coated bearing appeared to be in good shape although the bearing showed a few marks caused by hard wear. The engine was reassembled and runs made on Contract W-535-AC-12741 Item 6 at 2,700 rpm to check previous runs; then a friction run was taken. An Item 6 run at 3,000 rpm and 0 to 14 inHgG was also made and a friction reading taken at this speed. Total time on this bearing was now 15:44 hrs of which 9:35 were under power. Runs were to be made with Shell "Hot Acid Iso-Octane" gasoline to see what can be expected at 8.5:1 compression ratio with this fuel. Funs at 3,300 rpm were awaiting a new, heavier forked rod. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 212.]

1 Aug 1940. Haddad reported that the XO-1430-1 had been reassembled with two new reduction pinion thrust bearings and a Bendix PD-12B5 pressure carburetor. Runs were made at 2,000, 2,500 and 3,000 rpm to obtain coolant flow data. As both the XO-1430-1 and Continental XR-1740 sleeve-valve engine were using the same carburetor air measuring bottle, no official runs had been made recently as the XR-1740 was being given preference.

A sort run on the twin-cylinder test engine using Shell "Hot Acid Iso-Octane" gasoline at 14 inHgG showed a power increase. No other runs were made with this fuel. A new, heavier fork-and-blade connecting rod with a cadmium-silver bearing was installed, as well as new rings on the right piston. After a 5:30-hr run-in of which 2:40 hrs were under power, tear-down inspection revealed the blade bearing had flaked slightly. The engine was reassembled and Contract W-535-AC-12741 Item 6 runs were made at 3,300 rpm from 0 to 12 inHgG. When 14 inHgG boost was tried, the left cylinder head suddenly failed. The inner head jacket was cracked from the spark plug hole to the exhaust valve insert hole down to the undercut at the cylinder barrel top around to the intake valve insert hole. The jacket outside was also cracked about the same distance on the circumference. This was a new cylinder on which a deviation had been granted by Engineering Order X-312 Change 2, as its bore was about 0.002" undersize. Total time on this cylinder was 58:41 hrs of which 35:52 hrs was under power. The blade bearing had continued flaking, indicating a poor bond with the steel back. Total time on this bearing was 8:25 hrs of which 5:20 hrs were under power. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 213.]

10 Aug 1940. Haddad reported that a new cruise metering needle was installed on the XO-1430-1 PD-12B5 pressure carburetor to increase the mixture control range. Check runs were made at 1,800 rpm and 0 inHgG, 2,000 rpm and 4 inHgG, and 2,200 rpm at 0, 4, and 8 inHgG. Full throttle at 2,200 rpm was then tried for the first time. A new magneto was installed when the old unit's bearing and shaft failed. A different fuel pump was also required as the old one could not supply the pressure required by the carburetor. Runs were made at 3,000 rpm with 8 and 12 inHgG boost, but when 16 inHgG was attempted the required fuel flow could not be maintained. CAE was installing larger fuel lines in an attempt to overcome this. Previously-reported runs were made with the old float-type carburetor. The 3,200 rpm runs were being made with the new, heavier connecting rod as in the twin-cylinder engine.

The twin-cylinder engine was reassembled with a new oversize left cylinder, new compression and oil rings, and a new cadmium-silver rod bearing with 16 additional holes and four oil grooves in the blade bearing. The right-cylinder exhaust valve seat was re-cut to align it with the valve guide. A new exhaust rocker was installed on the left side as the other had two flat spots on the roller. Tear-down after a 5:50-hr run-in showed the blade rod bearing had started to fail; it was reassembled with a copper-lead bearing, lead coated on the inside, which had the same additional oil holes as the cadmium-silver bearing. After a run-in to 3,000 rpm and 8 inHgG there was hard wear on the blade bearing. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 214.]

20 Aug 1940. All XO-1430-1 spark plugs were changed and the engine was run at 3,000 rpm with 0, 4 and 12 inHgG boost. The coolant flow was erratic so the engine was disassembled for inspection. Three cylinders had slight coolant leaks between the coolant jackets and barrels but no leaks could be found on the cylinder interiors. The cam drive gear on the reduction drive gear shaft showed excessive tooth wear and was stoned. The sharp edges on the spur gears driving the camshaft bevel gear drives were also stoned. The engine was assembled with no parts changed and run at 16 inHgG boost. Air appeared to be leaking into the coolant but no further leaks could be found. The supercharger ratio was being changed from 6.0:1 to 6.45:1.

The twin-cylinder engine was reassembled with the rods and bearing removed on 26 July as the new, heavier rod was being machined 0.005" oversize and fitted with a new bearing. A run was made up to 3,300 rpm and 8 inHgG. This added 3:09 hrs to the 19:37 hrs already on the bearing. Inspection showed hard wear near the blade bearing parting line and piston ring wear. The engine was being reassembled with the same rods and bearing. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 215.]

A run at 2,800 rpm and 0 inHgG was attempted, but the engine was running rough; it was shut down to change spark plugs.

The twin-cylinder rods and bearings used in the runs reported on 20 August were not reused as the bearing crush was not acceptable. The new heavier forked rod was machined 0.005" oversize and the heavier blade rod was ground on the parting edge to remove the 0.015" chamfer; it was then rebored. A new copper-lead bearing, lead coated on the inside was installed. The engine was being run-in. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 216.]

28 Aug 1940. The XO-1430-1 was rim at 2,800 rpm and 0, 4, 8, 12, and 16 inHgG boost. This run was smoother than the last one before the spark plugs were changed. There were slight oil leaks at the cylinder bases and two cylinders looked coolant at the core plugs in the head tops. On teardown, the rod bearings showed hard-bearing spots. The reduction gear drive shaft was replaced by another from stock as the cam driving gear on it showed the same working as before. One compression and two oil rings were broken. They, along with six other worn oil rings, were replaced. The engine was being reassembled for a 3,000 rpm run.

The twin-cylinder engine was run at 3,300 rpm on Contract W-535-AC-12741 Item 6 to 16 inHgG boost and the friction measured. As the speed was brought up to 3,500 rpm the beam and oil pressure started to drop slowly. Inspection revealed the rod bearing had washed out on the crankpin side and the blade side was scratched. Bearing material was embedded in the crankpin and the rings on the left piston were feathered. A new copper-lead bearing was being machined in the forked rod at Muskegon. [USNARA RG342 RD1676 503-106 O-1430 390621-400828 Vol. 4. 217.]

10 Oct 1940. Bachle met with Neill and Prescott at MatCmd and stated that the V-twin intake valve springs were not sufficiently strong to prevent the intake valves from opening due to boost pressure. Design work was in progress on valve springs having a lower pressure increase rate and the same compressed spring loads as those in use. He also mentioned that the exhaust valve springs were operating at higher temperatures than those of the horizontal-twin; this excessive temperature resulted in the springs loosing tension. CAE proposed substituting stainless steel spring washers in order to reduce heat flow from the valve stems to the springs. This V-twin heating was apparently happening because its exhaust valves were at the top while they had been at the bottom on the horizontal twin. CAE was also considering a valve stem redesign that would limit molten sodium travel up the stem.

Bachle said that the horizontal-twin test using the original light connecting rod design made it doubtful that rod would work even with the improved bearing shells. Excess flexing appeared responsible for the bearing metal failure seen in the older rods; bearings using the heavy connecting rod design in the V-twin did not exhibit that failure. The idea of installing thermocouples in main bearing shells was discussed and MatCmd showed Bachle how such thermocouples were installed.

The V-twin fuel injection apparatus appeared to give better distribution than the carburetor used on the horizontal-twin; under similar conditions the horizontal-twin specific fuel consumption was about 0.47 lb/ihp/hr compared to 0.42 lb/ihp/hr for the V-twin. A effort was under way to install a similar injector on the horizontal-twin. Bachle stated that CAE had obtained ceramic spark plugs for experimental installation on the test engine as recommended by MatCmd. Operating the V-twin at the required output for the XO-1430-1 design made it difficult to secure a plug set that would perform satisfactorily; a better spark plug was required.

[USNARA RG342 P121634. 19 Oct 1940 Memorandum Report E-57-285-236, Conference Oct. 10, 1940, on XO-1430-1 and Twin Cylinder Engine Test.]

Conclusion

And thus the XO-1430 saga comes to an inglorious end. The engine spent eight years in development, yet it never flew, never passed a type test, and was still a long way from either when it was abandoned. It had been chronically under-funded by both the Air Corps and Continental. This led to a development process so protracted that by the time an end was in sight its requirement had disappeared. The XO-1430-1 was probably disassembled and its parts used in the XIV-1430. The wooden model was reported to be in the hands of a private collector.

If anything good can be said about the XO-1430, it is that it demonstrated that there was no wisdom in flat engines just so they could be buried in aircraft wings, and that high-temperature cooling was a fundamentally flawed idea. Even today, cylinder wall temperatures in excess of 250°F cause trouble. Unfortunately, the XO-1430 did not kill the separate-cylinder concept, which was carried on into its successor, and which caused the same bearing distress and crankcase-cracking. The XIV-1430 also suffered a protracted and troublesome development, and although it flew, it never entered production. Neither engine contributed to the WWII effort.

By contrast, during the XO-1430's development, the Allison V-1710, which the Air Corps funded at about twice the XO-1430's level, turned into a durable, useful, highly-produced engine that worked very well for low-level work (Bell P-39, Curtiss P-40), and high-level work also when used in conjunction with a turbosupercharger (Lockheed P-38).

For those interested in such details I have included the Purchase Orders and Suborders associated with the XO-1430 project. [USNARA RG342 RD1676 503-106 O-1430 Work Orders and Purchase Orders.]

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