Externally I can see that a considerable amount of the original motor remains. Certainly the cylinder head was replaced. As mentioned earlier in in a comment by Bill Hoddinott: “The original cylinder head of the GF was an unpainted Black Lightning/Shadow front head with standard size but polished valves and the inlet port opened to 32mm to match the carburetor.” We should also assume the barrel utilised now is not the original one. And obviously the piston was changed and the engine lost its special Vibrac connecting rod. Internally I’m eager to see what it looks like and keen to look for markings and stampings in order to ascertain how many of the parts therein, if any, might be original to 2751.
Additional stampings: #1 is at present a bit of a mystery but must be with regards a note on the Engine Spec Sheet (see below). #2 is the mating number – not visible on on the crank case halves until the barrel is removed. #3 are, I believe, inspection stamps. Perhaps readers of this blog could further comment?