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).
Proposal for modifying an engine unit to a large bore specification for Wor's Car.
| Identifier | ExFiles\Box 107\1\ scan0307 | |
| Date | 30th May 1935 | |
| To RHC.{R. H. Coverley - Production Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}20/KW.30.5.35. X560 Modification to the Engine Unit in Wor{Arthur Wormald - General Works Manager}'s Car. We are proposing to convert the engine unit in Wor{Arthur Wormald - General Works Manager}'s car to a large bore. Being a 20/25, when we increase the bore it is necessary to alter the cast passage through the block, otherwise the bores will break through into this. We want to retain a hole about 1/4" dia. as it may be useful for a control shaft. Having done this, it means that the carburetter must be transferred to the exhaust side of the engine. We have already running a system which operates satisfactorily under these conditions. With the object of making the changeover in the quickest possible time, we give you the following specification :- (1) Large bore 20/25 cylinder block to be fitted, the hole between the centre cylinders to be decreased the chamfer at the top of the bores to be reduced as previously on large bore units. It is proposed to use the crankcase as at present on Wor{Arthur Wormald - General Works Manager}'s car, and fit the cylinder block to it. This means that the timing gears, crankshaft bearings, etc., will be as before. (2) A liner to be prepared to go under the cylinder block, .150" thick, and a second one .075" thick, the liners to be of aluminium. This is to enable a standard cylinder head to be used for the correct compression ratio to be obtained with the large bore. We presume that the existing cylinder studs will accommodate an increase in the cylinder block height of .150", without requiring to be lengthened. (3) Four-port manifold and exhaust pipe, as fitted to 20-G-IV, but with improved exhaust hot-spotting, a drawing for which will shortly be issued. (4) Aerolite pistons, 3 1/4" bore, as fitted to Bentley I. We are obtaining these. (5) Large bore gasket, suitable for 20/25 head, E.55315. We have ordered these. | ||