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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).
Page two of a document detailing engine valve timing tests and specifications.

Identifier  ExFiles\Box 33\4\  Scan101
Date  26th November 1927 guessed
  
contd :- -2-

Al. piston was exactly on T.D.C., and A.{Mr Adams} side camshaft drive engaged so that Al. inlet valves were just about to open with a .010" feeler between the rocker and the valve stem.

This was repeated on B.6. cyl. at the succeeding T.D.C. position. Repeated tests proved this to be a very satisfactory method - when checked with .030" clearance the average valve timing was between 38° A.B.D.C. and 39° A.B.D.C. for the I.C. position. The limits for the I.C. position for these tests were 35° A.B.D.C. to 40° A.B.D.C.

(b) Average timing.

.020" clearance and .010" feeler (.010" clc. actual).
++
Inlet opening 6° B.T.D.C. Variation 1/9° B.T.D.C.
closing 53.5°A.B.D.C. " 48/60°A.B.D.C.
Exhaust opening 46° B.B.D.C. " 39/54°B.B.D.C.
Exhaust closing 19° A.T.D.C. " 12/25°A.T.D.C.

Hitherto the D.O. have called for a timing with .010" clearance.

In the case of the RR.F.Xl. and F.Xll engines, this has the merit of simplicity - a .010" feeler has merely to be inserted in the standard working clearance and involves no alteration in the tappet setting.

It is understood that the timing given is for checking purposes only, and is not intended for use when setting the camshafts.


++ Much smaller variations are obtained when using .030" clearance - an average for these can also be quoted, but no check is obtained on the toe of the cam.


Hs{Lord Ernest Hives - Chair}/V.Halliwell.
  
  


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