If you are going to o ring the engine, at least do it correctly.

You o ring both the block and the heads. The wire goes in the heads and the groove in the block is a receiver groove.

Over the years I've seen this done wrong so many times is just plain stupid. You o ring both.

If a machine shop tells you that you don't need both GET A NEW SHOP.


Also, if you were my customer I'd tell you that you don't need much gasket to seal what you are doing. If you need compression, mill the heads and block.

You don't need o rings, especially o rings done wrong.