B33 Cylinder Barrel Shim

[SimonJH]

Hi I'm a real novice so sorry if a dumb question.

I'm rebuilding a 1955 B33 I bought completely stripped down. I have a shim with the parts which is clearly designed to fit between the barrel and crankcase. It's quite thick - 1/16th of an inch. In the parts manual it doesn't refer to a shim, just a gasket, although the Haynes manual does refer to a shim in the diagram, but no gasket.

The cylinder has been rebored and never used since rebore.

I'm assuming I should just fit this shim under the barrel? if so should I use a gasket on both sides of the shim ?

Thanks
Simon

[Bigsingle]

My B33 Has a spacer , I think it's best to check for squish at the cylinder head it's nice to have .040 clearance , and can be checked with solder , but with it will lower your compression ratio , which can be calculated. Mine has the grey-max type silicon on both sides , or you could use a gasket on both  sides . Cheers .

[Rog1]

My M33 (same engine) has a shim of about that thickness. After my rebore I installed it with a gasket on each side.

[JulianS]

The piston was changed and the shim/compression plate introduced on a service bulletin from 1955 below.

The early design piston 65 1692 was 6.5:1 compression. The later design piston 65 1660 was 7.5:1 compression and when used with the plate brought compression back to 6.5:1.

This is for engines with short conrod.

[TTJOHN]

Nice to see you have found the modification, I was going to suggest that maybe someone wanted to reduce the compression, as they sometimes do.

[SimonJH]

OK thanks everyone for great information.

I'll fit as advised.
Thx
Simon