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Copper Hemi head gaskets

Fran Blacker

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Trying to reduce compression on my Hemi. It has 12.5 to 1 TRW pistons, went assembling engine put a steel embossed gasket on first then a .040 dead soft copper gasket. Used high tack gasket sealer on all 4 sides and assembled it. Compression is now about 11 to 1 with a cranking pressure of 215 psi to high for iron heads I believe??? Been thinking of buying a set of MP aluminum heads and running the same head gasket setup with maybe .010 thicker steel or copper heads gasket combo. Don't really want to change pistons because might end up boring block to .60 over. The TRW's have .011 piston to wall clearance now, max p/w is .013 on these early 70's pistons. Maybe able to go .040 over but then a rebalance of engine is in order? Doubt I could get pistons the same weight, custom wrist pins to bring weight up to old piston weight?:eek::screwy: Little leery of using Cometic head gaskets because of block surface finish.
Haven't had any sealing issues with the copper steel head gasket combo. Just wondering/ want opinions whether the switch to aluminum heads will work ok.
 
Use Cometic head gaskets. You can get any size between 0.027" to 0.140" and different bore sizes too. 800-752-9850

I see your last part now. Was the block surfaced before, and if so, how was it surfaced (what machine or method). The old Storm Vulcan 85B with 20 or so carbide cutters can leave too rough of a surface. If a superabrasive (CBN) like I use, the surface should be smooth enough.
 
Use Cometic head gaskets. You can get any size between 0.027" to 0.140" and different bore sizes too. 800-752-9850

I see your last part now. Was the block surfaced before, and if so, how was it surfaced (what machine or method). The old Storm Vulcan 85B with 20 or so carbide cutters can leave too rough of a surface. If a superabrasive (CBN) like I use, the surface should be smooth enough.
The was decked in 1971 so surface is pretty rough if I remember when I reassembled it. Talked to Cometic water sealing is the concern, recommended a spray sealer. The steel copper sandwich thought would seal better. The embossed ribs would crush the copper more with the steel under it. Really don't want to use O-rings. Milodon says you don't need them with their copper gaskets.
 
The was decked in 1971 so surface is pretty rough if I remember when I reassembled it. Talked to Cometic water sealing is the concern, recommended a spray sealer. The steel copper sandwich thought would seal better. The embossed ribs would crush the copper more with the steel under it. Really don't want to use O-rings. Milodon says you don't need them with their copper gaskets.
Yea, no superabrasives back then. The only other thing that would leave a smooth enough surface would be a grinder. When you take the heads off, run your fingernail across the deck. If it is really rough, MLS won't work, if it is pretty smooth, it was probably done on a grinder. Only other option is the have the block decked again. You don't need to hog it out, just get a smoother surface finish.
 
Fran have you thought about some epoxy to level the rough? I’ve repaired a deck with JB weld that had some minor nicks which had caused a head gasket failure. That was 3 years ago, 12.8 CR and used cometic gaskets when going back together. Ive made a repair like this on a Detroit block the same way, a few decades ago.
DVW has also made similar repairs the same way.
 
I will have to look into this style head gasket maybe. Mine is approx 11.5 -1
and would like to get in back down in the mid 10 - 10.5 range if I could.

Previous owner told me it has OEM steel shim head gaskets on it now
 
What does it actually CC out at? I would start there if you haven't already, otherwise I wouldn't bet on it being 12.5-1.

What are you running for camshaft?
 
I measured it to 11 to 1. Cam 246* @.050 536 lift. The 215 lbs cranking psi with iron heads is bothering me.
 
Out of curiousity, what did it cc out at? Do you know what centerline the cam is installed at?
 
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