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).
And comparing engine valve sizes for various models.
| Identifier | ExFiles\Box 17\6\ Scan027 | |
| Date | 6th March 1928 | |
| R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} c. to BJ. Hs.{Lord Ernest Hives - Chair} BY.{R.W. Bailey - Chief Engineer} X7060 E3/M6.3.28. EAC.10 & INDIA 3. VALVE SIZES X17060 X.5060 In checking over the dimensions of LeC.2509 I find that the exhaust valve dia. should be 1.700". This makes it that we have a 10% different in inlet and exhaust valve dia. on EAC.10, the inlet being 1.9" - see fig. 1. LeC.2523 attached. EAC.14 has both valves 1.750". F.10 has a 5% difference in dia. between inlet and exhaust, as also RR.H. 10% is the difference recommended by some authorities, but I am not sure that we have been wise in shewing the full amount for EAC.10. However we propose to leave it so unless we hear from you to the contrary. The alternative would be to make the valves 1.85 and 1.75 inlet and exhaust respectively, as in fig.3. Regarding India3. it is hardly worth while having a smaller difference than .1" between the valve dias., and this gives us 1.35" and 1.25, or an 8% difference shewn in fig.3. These are the valves we are providing in the design of India 3. cyl. head. The present 20 HP. valves are 1.2 dia. The tested larger valves are 1.4 dia., but these will not go into the existing cyl. centres. E.{Mr Elliott - Chief Engineer} | ||