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Eric, The expansion rate of copper is immaterial. Headbolt/cylinder stud 'stretch' is the holding power. Oil will wick past copper no matter the sealer,...retorqing is only necessary with fiber type materials that compress beyond a certain point. That is the main reason for multiple shim type steel gaskets. Some sealer is commonly used with fiber type gaskets,....but of questionable value,...can't hurt. A chemical can never do what a mechanical seal does ( I'm not talking thread sealant) Probably 99% of head sealing problems not of an initial mechanical nature, are caused by detonation,......period. Take this to the bank. Turbo motors not detonating can produce unbelievable power with stock components,...and reliably. You MUST have close fuel mixture and ignition timing controls to keep combustion normal. You can calculate proper timing exactly from ideal normal and boosted induction pressure. Do you ever wonder how 11:1 compression 28 psi boost motors live ? Electonics. cya Jeff Churchill J.C. Performance 617-06 Bicycle Path Port Jefferson Station NY 11776 USA tech: 516-928-6679 or 516-928-9863 website: http://www.jcperformance.com/ On Sat, 22 May 1999 02:02:36 -0400 (EDT) MCycleTech@webtv.net (Eric S.) writes: >Two cents from the peanut gallery. I agree with all the input, and >admit >that I know jack about T/Supercharged systems first hand. Another >thought included is copper has a quicker expansion rate than say your >cyl. "barrel's". And temp. ranges from parked warm up, to operating >conditions, dynamic cooling, etc., call for retorquing. Not to >mention >extreme conditions. Ideally no sealer is required for apps. like head >gskts. >, if condit. & materials are on the money. But I would imagine >something >"tackier" for sealing like SUZUKIBOND 1207B (or equiv.) would be >more >durable than Y.B. 4 or 5, the latter being forms of semi-curing >sealants >that cannot hold comp. press. as adequate. Multi-layer treated steel >gskts (like newer GSX-R's) are ideal (tuneable C.R. a plus) but as >somebody said, are prob. not available. BUT LIKE I SAID, IT'S ALL >THEORY!!! I'll try to do a little research on it. GOOD LUCK! > >