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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).
Comments and analysis on a B.M.W. cylinder head, comparing its component count to a Bentley engine.

Identifier  ExFiles\Box 134\1\  scan0041
Date  16th November 1937
  
To By.{R.W. Bailey - Chief Engineer} from Rm{William Robotham - Chief Engineer}/Ed.{J. L. Edwards}
c. Da.{Bernard Day - Chassis Design}
c. JNR.{Charles L. Jenner}

Rm{William Robotham - Chief Engineer}/Ed.{J. L. Edwards}7/MH.{M. Huckerby}16.11.37.

B.M.W. CYLINDER HEAD.

Comments on the above head, sketch attached, are as under:-

(1) Breathing - This should be remarkably good judging from the straight through downdraught inlet port employed, there being practiaally no obstruction to the incoming gases. The exhaust port is also fairly free, and quite good scavenging should result.

(2) Valve Size - The valves are set at an angle of 80° to each other enabling some 30% larger valves to be used for the same amount of metal between the seats.

(3) Detonation - The valve arrangement enables a central plug position and hemispherical head to be employed, which gives good volume distribution coupled with a short flame travel. Detonation would be expected to be very good.

(4) Idling, tick over and pick-up - Due to the ease with which the fresh charge gets into the cylinder, and the proximity of the plug to the inlet valve, these qualities would probably be very good indeed, and good economy might also be expected.

(5) Number of pieces.

PIECE. BENTLEY. B.M.W.
Valves, cotters etc. 12 12
Push Rods 12 18
Rockers 12 18
Rocker shafts 1 2
Rocker pedestals 7 14
Rocker covers 1 2
Valve springs 12 24

TOTAL 57 90
  
  


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