Performance Valve?

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In most builds you don't want to raise the compression ratio so you'll want one that's 1.37mm + whatever they cut from the block + whatever they cut from the head. You don't want them to take any more material off the block than necessary

Note that while metal head gaskets are VERY finicky about the deck surface and smoothness the HKS' Stopper HG (the one I suspect you're looking at) is the pain in the ass. I think it requires an RA finer than 18 or 15.... a lot of older shops can't produce this and if it's rougher than that it WILL blow.

Unless you're reusing a given MHG you want to read the MSDS of ANY chemical before you apply it to your block, head or HG.... Most gasket dressings contain chemicals which will cause the sealant coating which most MHGs already come with to crack, ripple, bluster, peel, or just turn to an easy to blow out liquid goop..... B A D. I'm a Hylomar fan myself; I know some of their products are safe for Viton and similar coatings but a lot of their products aren't be careful if you choose to add a sealer, it's a stupid reason to have to rebuild. I advise against it unless you have a really good reason for it... As I said, most MHGs already have a sealant on them anyway.