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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).
Engine component failures and their running hours.

Identifier  ExFiles\Box 134\2\  scan0145
Date  23th June 1937
  
-7-
Against good slow running we have the size of inlet port and valve. If high speed power is to be maintained and full advantage taken of the large port and valve, a large induction system will be necessary with a corresponding drop in gas velocity and slow running properties. A smaller valve has been called for to see what effect this will have on power output.

(7) MECHANICAL FAILURES.

(i) Valve Springs. Three failures of inlet springs, one outer after 18½ hours and two inners, one after 254 hours and one after 193 hours.

(ii) Inlet Valves. No failures and seats usually in good condition. Occasionally a circumferential ridge was seen corresponding to the seating in the head.

(iii) Push Rods. Two failures due to an adverse accumulation of tolerances giving too long a push rod, and causing fouling on the edge of the rocker cup. Running times 212 hours and 30 hours.

Rocker Bush. This was found to be cracked after 255 hours.

Bottom Tappets. These were found to be very badly worn indeed after 500 hours, and were replaced. The exhaust tappet was worse than the inlet.

Valve Seats. The inserted valve seat in No.3. alum head worked loose after 86 hours. Hammering of the exhaust seat with the 1.500" valve was very bad after 575 hours' running, and appeared to have developed very quickly.

Bottom Tappet Spring. One failure after 416 hours.

Pistons & Rings. Two piston failures were experienced, one due to inadequate cooling between exhaust port and block after a 50 hours' endurance, and a second seizure after 141 hours, due probably to a very severe water leak in the gasket. One top gas ring also failed after 90 hours, cause unknown.
  
  


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