I have a G3L in unrestored 50's army paint. It has a G3 rockerbox, the bike has not run in years so I am checking things out before I get it running. The cylinder head is missing a few fins, however the bike came with 2 good condition cylinder heads, one of which I fancy putting on the bike to solve the broken fin problem. Trouble is these spare cylinder heads (one being NOS ) don't accept the 7 bolts that hold the rocker box down. The cylinder head that was on the bike is marked internally with an X, the two others are marked AMC. Any ideas ?

email (option): ggoodwin68@gmail.com

I certain WOG3 and G3L rocker boxes are interchangeable.

WOG3 has inspection caps same as the one on the oil tank filter.

post up some pics.

of course what you really want is a cast iron rocker box..............

Its definitely got inspection caps.

email (option): ggoodwin68@gmail.com

well it should fit, i suspect the other heads are later ones.

pictures are best

My 1940 G3 had a G3L rocker box on it when I got it and I've now swapped it for the correct G3 one with the inspection caps, so I know for a fact that they are interchangeable .

I reckon its the thread on the cylinder head that's the problem.

email (option): ggoodwin68@gmail.com

"When were these cast iron rocker boxes introduced? together with the cast iron timing cover?"

no idea, but my bet would be 42/3 when alloy was needed for other more urgent purposes.

I have a cast iron timing cover for sale if anyone wants one.

I fail to see how the thread is a problem.

A new set of rocker box bolts seems to have sorted it out.I can now put on the cylinder head I want.

email (option): ggoodwin68@gmail.com