From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Modifications to prevent big end seizures in 4¼ litre Bentley engines.
| Identifier | ExFiles\Box 115\3\ scan0197 | |
| Date | 8th March 1938 | |
| H.S. c to BY.{R.W. Bailey - Chief Engineer} c to Rm.{William Robotham - Chief Engineer} c to EHC. SWDL.{Len H. Swindell} Peiles Hd{Mr Hayward/Mr Huddy}/SB{Mr Bull/Mr Bannister}23/HR.8.3.38. 1020. re 4¼ LITRE BENTLEY BIG END SEIZURES. ---------------- We have been considering the possibilities of applying modifications to 4¼ litre Bentley engines to avoid big end seizures without incurring a great deal of expense, and we would like to make the following suggestions. Our experience indicates that the greatest assets are:- 1. LARGE TYPE OIL PUMP. We have never seen or heard of a big end failure in service where a large oil pump has been fitted. 2. EXTRA HOLE IN CRANKPINS. Devereux's engine showed distinct signs of heating up on the crankpins on the opposite side to the existing hole, and an extra hole would probably have saved it. There have been 9 cases of wrecked engines on 4¼ litre cars, involving an expense of just over £1,000. As all these were either No. 2 or 5 big ends it seems to us unnecessary to drill the crankshaft on all journals as at present, provided Nos. 2 and 5 crankpins were drilled. As the big end failures experienced so far are not confined to any particular series, it would appear that the other modifications introduced from time to time (such as increasing the groove in the intermediate bearings from 240º to the full circumference, and the holes in the main journals) are not in themselves of great value in preventing big end failures. Therefore, we suggest that in dealing with the 800 cars in service which are susceptible to big end failure, we fit the large capacity oil pump and drill extra holes in Nos. 2 and 5 big ends in position in the engine. -continued- | ||