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).
The condition of Engine Unit No. C.10 after 7,000 miles, detailing issues with valve seats, ignition, and pistons.
| Identifier | ExFiles\Box 5a\3\ 03-page055 | |
| Date | 30th September 1931 guessed | |
| ENGINE UNIT NO. C.10. The engine has remained very smooth during the last 7,000 miles. There have been no marked detonations on acceleration from slow speeds. The torque reaction effect is very small and has remained consistent. The power of the engine has remained a good standard. There have been times when erratic slow running of the engine has taken place due chiefly to the exhaust valves remaining open due to the distortion of the valve seats and loss of tappet clearance. We have also had misfires which we believe has been due to the ignition coil becoming faulty. This will have to be verified by a bench test, as we have not been able to get consistent results. We have examined the front suspension of the engine and we have not been able to detect any weakness or faults. We have not had any reoccurrence of the pivotbracket support from the gearbox causing the rattle or knock, since we lubricated as reported previously. The engine has been free from thuds or any marked crankshaft period during the latter part of the mileage. PISTONS to LOP.1.55804. We have not during the mileage heard any piston knocks either hot or cold. Examination of the piston tops show them to be covered with a fair amount of carbon. We have not had any case of over-oiling. A test of 10 mins. slow running, after each run, has been made, and the exhaust has remained free from any smoke. VALVES & FITTINGS to LOP.1.55577. The exhaust valves have given trouble by distortion of their seats and losing the tappet clearance. The cylinder head has been dismantled twice to ascertain the cause. We have found that this is due to the valve seatings becoming more recessed in the cylinder head, thus allowing the valves to project further through. This fault is only peculiar to the exhaust valves, the seatings of the inlet valves remain the same. The cause is not therefore due to stronger valve springs being fitted. No.5 exhaust valve seating was so distorted that it was not possible to regrind the valve in. The exhaust valve guides have also worn considerably, the wear taking place chiefly at the valve seat end of the guides. The inlet valves and guides have remained in good condition throughout the mileage. CYLINDERS & CYLINDER HEAD. Examination of the cylinder bores show them to have been well lubricated and fairly evenly. There are no signs of any score marks on the walls. The cylinder head, with the exception of the exhaust valve seats, has given no trouble. We have had no sign of any water leaks. | ||