Rolls-Royce–Bentley L-series V8 engine as the "six and a quarter" litre engine. When new, the Rolls-Royce/Bentley V8 was rumoured to be an American engine design licence-built, but it was developed in-house by Rolls-Royce and Bentley engineers. This can be seen in its design characteristics, with features like an aluminium alloy cylinder block with wet liners, gear-driven camshaft, (initially) outboard spark plugs and porting inspired by the Rolls-Royce Merlin aircraft engine. The bore spacing of 4.75" was unlike any American V8 engine and the firing order was 1-5-4-8-6-3-7-2 something uncommon in any period American OHV V8. The deep skirted crankcase design is also rare with
Rolls-Royce 25/30 Rolls-Royce 25/30 The Rolls-Royce 25/30 built between 1936 and 1938 is an updated version of the 20/25 with larger engine to provide more power, as often, over-large bodies had been fitted to the earlier model leading to complaints about its performance. The in-line 6-cylinder, overhead-valve 25/30 hp engine is similar to that used in the 20/25 but increased in capacity to by increasing the bore from to , with the stroke remaining at . The compression ratio is 6:1. A single proprietary Stromberg downdraught carburettor replaced the Rolls-Royce one, and magneto ignition was no longer fitted, but a standby coil