Rolls-Royce Archives
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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).
New 75 m/m cylinder head design, its compression ratio, and a potential valve clearance issue.

Identifier  ExFiles\Box 132\4\  scan0259
Date  7th July 1941
  
WYMAN (crossed out) Rather high? Rm{William Robotham - Chief Engineer} (circled) 1124
To Rm.{William Robotham - Chief Engineer} from Jnr.{Charles L. Jenner}
c. to Rm{William Robotham - Chief Engineer}/HH.
RM{William Robotham - Chief Engineer} TOO HIGH Jnr.{Charles L. Jenner}2/SW.7.7.41.
6.4:1 is now on the limit with present day fuel
Rm{William Robotham - Chief Engineer}/Wyman.
75 m/m.{Mr Moon / Mr Moore} Cylinder Head.
We have made a design of the original type Cylinder Head to supercede the intermediate type. A compression ratio of 6.75 : 1 has been chosen as suitable for this size of engine.
The form of the head is exactly the same as for the 3 1/4 bore, but shallower, it will be noticed that the inlet valve will foul the piston if it remains stuck open at full lift. We have to accept this with a rationalized cylinder block.
Jnr.{Charles L. Jenner} (initials)
Original of PL.753 to Rm{William Robotham - Chief Engineer}/HH.
Prints to Ashby and Jnr.{Charles L. Jenner}
  
  


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