Pocketing block for 12g940 head
Turbo Mini Forums

Out of interest does anybody know what shape to grind the block out around the exhaust valve. I believe 220thou down is the top ring but should the 998 head gasket shape be used as a template, or should you grind just enough for the valve to drop into?

Also does this post make any sense...............LOL!

You need to use the 1275 gasket as a template, as you are using the 1275 cyl head.

Also you shouldn't grind the pockets, they need to be properly machined on a milling machine really.

Depth that is required depends on what cam you plan to use.

Aha. Thankyou very much. So if i was to lay the 1275 head gasket over a few studs and scribe around the inside that would be the amount that needs to be machined?

Not really no.

Generally the pocket is machined just big enough to clear the valve, not the gasket overhang.

If your running std cam and rockers,you can do away with pocketing and sink the exhaust valves .040" into the head with a bit of reshaping to the combustion chamber.

pockets would be better though

Metro turbo weekend driver,Mini turbo in the making again!

That all makes sense thanks. The basic story is i had a block machined for 12G940 head when i was building it but ran it with a std small bore head, MD266 cam, HIF 44 carb, LCB exhaust and it was putting out 46BHP. All i did was change to the other head when one became available and it then put out a staggering.................. 28BHP. Tried 2 heads and both done the same

Doesn't really matter now as im going the turbo route, it would jus be nice to have some theories on what went wrong.

Thanks again.