Most Boost Gasket Engineers I have talked to over the years assume that the head will lift approximately .007"-.010" and design into their MLS gaskets enough room to seal at .012". Some of this info is for a diesel engine at high boost levels that the average boosted engine would not experience.
Even if you install a Gas ring like a diesel uses, if the ring diameter is too small, say .060" tube diameter, then the ring when ovalized with head torque will only have .007 to .010" to "follow the head". Once the ovalized state is converted to a round shape that .001" more movement = .001" leakage.
Diesel engines have now gone to a .093" tube diameter and have .015" to .020" ovalization of the ring. This allows the head to move over .010" upward and the head will still stay sealed.
Copper gaskets and wire rings have no ovalization of the wire. They use the concept that a Labyrinth created by the wire imbedding into the copper will impede the gas leakage enough to basically seal the head under most conditions in racing for a period of time.
You might have more leakage on a low boost system with a copper gasket/wire vs a higher boost situation because the leakage rate will be the same for both cases but the high boost system will see more sealing effect because the leakage ratio will be much less with the high boost engine.
We have used NO GASKETS and the Diesel Gas Ring technology for years on our Single Cylinder Engine Testing.
Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught
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