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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).
Valve timing tests and clearances for F.XI and F.XII engines.

Identifier  ExFiles\Box 33\4\  Scan100
Date  26th November 1927
  
To RG.{Mr Rowledge} from Hs{Lord Ernest Hives - Chair}/VH.
c. to BY.{R.W. Bailey - Chief Engineer}
c. to EP.{G. Eric Platford - Chief Quality Engineer}
c. to E.{Mr Elliott - Chief Engineer}

X/1770

Hs{Lord Ernest Hives - Chair}/VH1/LG26.11.27.

RR. F.XI and XII - VALVE TIMING.

Further to our report Hs{Lord Ernest Hives - Chair}/VH1/LG6.10.27. we have carried out tests :-

(a) To investigate the possibility of timing these engines by setting the camshafts A.{Mr Adams} side and B. side in a position corresponding to T.D.C. on A1. and B6. respectively.

(b) To obtain an average timing I.O., I.C., E.O., E.C., suitable to quote for comparison purposes.

These tests have been made on the F.XI and F.XII production engines (Aug.-Oct.1927) to meet requirements (1) and (2) in the report referred to above.

(a) The camshafts were first timed in the ordinary way (Expl: Dept:) setting I.C. 38° A.B.D.C. rising a .030" clearance. By this method we have found we can set the valve timing accurately to get the best power out of these engines.

With the piston exactly at top dead centre (end of exhaust stroke) the exhaust and inlet tappets were set so that there was just .010" clearance.

A careful record of all clearances were taken when the engine was turned so that the rockers were resting on the 'back' (base circle) of the cams, before re-setting the tappets to the standard .020" clearance.

The results obtained varied between the following limits :-

Exhaust base circle clearance .057" to .073"
Inlet " " " .023" to .028"

shewing a considerable variation in the case of the exhaust tappets but quite consistent readings for the inlet tappets. The average clearance was between .025" and .026" in the case of the inlet tappets.

Following this, tests were carried out timing the engine by the new method. With the engine un-timed to commence with, the inlet tappets on A1. and B6. were set with a clearance of .025". The engine was turned until contd :-
  
  


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