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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).
Letter from Lycoming Manufacturing Company discussing their methods for engine valve cooling.

Identifier  ExFiles\Box 174\2\  img296
Date  6th December 1938
  
1360.
LYCOMING MANUFACTURING COMPANY
WILLIAMSPORT, PA.{Mr Paterson}
POWERED by LYCOMING

December 6, 1938

Mr. W. A.{Mr Adams} Robotham,
Rolls-Royce Ltd.,
Derby, England.

Dear Mr. Robotham:

Your letter of November 18 has been received and we thank you sincerely for the tribute you pay to our product.

Referring to the second paragraph of your letter, would advise that we have not found it necessary to use sodium or copper-cooled exhaust valves to get our high output. We use the standard austenitic valve steel which is generally used in this country in engines for both passenger car and truck service.

In regard to valve cooling we find that one of the most important things we do is to cool the jig, in which the valve seat is machined, cool - which we accomplish by directing the water pump flow into a tube which is inserted between the valve ports and the cylinder barrels. This tube is elliptical in shape, merely to be able to take advantage of the greatest cross section between the cylinder and intake ports, and small holes - about 5/32 to 3/16" - are drilled immediately under the exhaust port so that the water due to the pressure from the water pump is directed immediately against the hottest surface. This has materially reduced our temperatures at this point.

Another thing which has aided materially, we believe, in keeping our exhaust valves cool is complete burning of the mixture within the cylinder, which is accomplished by the shape of the combustion chamber and proper location of spark plugs.

While some people claim that you do not need much clearance around the intake valve head on the side away from the cylinder, we find that the space around the perifery of the valve head is more important than the space over the valve head, and in our design we merely allow sufficient clearance between the valve head and the lift postion and the cylinder head to permit a slight over-run of the valve - a matter of about 1/32 to 3/16 of an inch.

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