AJS & Matchless Owners Club

Hi there,

I've picked up a 1953 m20 engine, generally good condition but the heads need a lot of work, many fins broken off, carb mount needs work etc. I've got a second pair which are much better condition but from a later year.
I think I already know the answer, but could the later heads be used? The differances are stud holes, on the '53 5/16 diameter, 7/16 on later heads, the stud spacing slightly different also, but later heads still seem to seat on the studs and barrels. Another differance is the barrel spigot recess, 73mm on the '53's and 76mm on the later. The combustion chamber height is the same on both, as are the valves.

This is my first amc twin so have little knowledge of the model changes. Could these be made to work successfully?
Many thanks
Stuart

Think you maybe getting a little confused over sizing. The early barrel/head stud spacing was the same up to 1955 and suds were 5/16" From 56 to 63 the stud spacings were wider but the stud size remained at 5/16". From 64 on the studs went to 3/8" but the centres remained as was. The spigot on the early barrels was 73mm and from 60 on it increased to 76mm.
Basically you require heads up to 1955, anything later won't fit.