Pistons come right to top of bore BK450 gasket overhangs bore a little Middle cylinders 73mm bore not offset.
Do I run with it till it fails if it does or go with a cometic gasket that doesnt use fire rings.
Finish on head and block is very smooth but not measured.
So close and this issue raises its head

Keith Calver knows this issue. Has a good article on it about using a head gasket as a guide for boring.
Not many do here it seems

Bore of a BK450 gasket is 73.5mm I just measured a couple.
So even if not offset bored, there's probably not much in it. My 1360 motor is also 73mm bore, not offset and never had a BK450 gasket failure. Has been to 8000 a few times. It does have .010" deck height though.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Cometic C4148 gaskets are 74mm and are available from .030" thick . Not cheap but do the job

Thanks guys Will go cometic .Its bloody hard to machine the pistons to get deck clearance once they are pressed on the rods lol.

nahhhh mate, just put them at TDC and run a rasp over the lot

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Thanks guys All redone today with a 74mm cometic .027 that I didnt know existed Will be all fine now as my local machinist insisted on decking the block and head to a mirror finish.

Isn't a belt sander a better option?

fwoar, that's a sh*t hot idea - I can hold the sander in one hand and my beer in the other

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did I tell you that I won a trophy?