Britbike forum Forums Thread Like Summary - Cylinder block warpage A65?

Hi all.I am having the devil`s own job getting my A65 cylinder head gasket (copper) from blasting oil out after 10 minutes of riding. I recently had the cylinder head nicely skimmed , annealed the copper gasket and blew a mist of copper spray on it. Retorqued the head after a little warm up in shed. The cylinder block is a used one i purchased so who knows. My question is -do cast iron cylinder blocks warp? I couldn`t see any light under a ruler,but my eyesight is a bit ordinary now.My torque wrench is old as me. Cheers, Max.

Hi Mark. Find a new machinist!

not what you want to hear but the only way to find out is pull barrel , get a good thick piece of glass ( you would be surprised how flat plate glass is) . Use making blue on the gasket face . put a sheet of something like 220 grit paper on the glass and give the cylinder a bit of a swirl around (get someone to hold the paper from moving) .. that should show if you have high/low spots ie warpage ...but if you go to the effort of pulling the cylinder may as well get a MINIMUM clean up skim on it ... not a big job.

they can warp if they have had a big overheat in their life

Are you using good quality thigh temsile head fasteners with nice thick high tensile washers under them ?

Thanks Allan. Always anneal them. And now it`s time for a beer! Cheers Max

Get a 6" deflecting bar tension wrench
I still have the one I bought back in 1968 and it is still accurate
Spring loaded ones must be backs off to 0 every time they are finished with because the spring will shorten if left compressed , just the same as a valve spring will develope a set even in an engine that has not been run for 20 years .
I think just about every BSA club member has borrowed it at one point in time
You should realistically avoid using the top & bottom 10% pf any scale and a 6" or even 8" will have you reading the 20 to 30 ft lbs fairly well mid scale
Also the shorter leverage gives you better feel for the all important method of tensioning a BSA
Tighten till the thread goes loose then back off 1/2 a turn
Warre & brown are still marketing their signalling deflecting bar tension wrenches which is what I have.
One under their brand & the other branded Repco .

Flat ≠true and true ≠ flat
The bore has to be ead square to the bottom of the flange ( mating surface ) and the bottom of the flange has to be parallel to the head
This of course assumes that the crankcase mouth is true to the crankshaft
In practice almost none of these will be spot on but close enough not to cause you grief