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 to Leyland Motors Ltd. detailing specifications for screwed-in inserts in aluminium cylinder heads.
| Identifier | ExFiles\Box 140\3\ scan0231 | |
| Date | 30th November 1938 | |
| 1175 EXPERIMENTAL DEPARTMENT. Rm{William Robotham - Chief Engineer}/Cwdl.15/JH. 30th. November, 1938. Mr. Pilkington, Leyland Motors Ltd., Leyland. LANCASHIRE. Dear Sirs, In reply to your letter of the 22nd. we give herewith some information regarding screwed in inserts in aluminium cylinder heads. Regarding your first query as to whether any pressure is needed to screw in the insert when the head has been heated up to 300°F, very little pressure is required until the conical face is reached, when it should be given a good snap home. Features which we consider are important in maintaining tight seats are as follows - (a) Both the head and the seat should have full form threads. (b) The interference size of the seat thread on the head is for our valve dimension, .003 on the diameter. (c) There should be ½° interference in the conical seat angle between the head and the valve seat, hence when fitting the insert this should be thoroughly tightened home. (d) That the necessity for having a high expansion seat material such as N/MC or alloy bronze to follow up. the aluminium head expansion is a fallacy. Lower expansion seats of 'Silichrome' (S/SLV) or S65 steels are more suitable in keeping a tight seat. Cont'd.{John DeLooze - Company Secretary} | ||