Solid Copper head gaskets work best. There’s a company SCE that will make copper gaskets for anything, if you don’t see them listed for the Cad.
Second Rand Man..I always O-ringed my blocks, but that was just personal preference. Many motors have not been O-ringed and worked jus fine on the street.
I've put a lot of miles on blown big block chevys with that level of boost, and stock gaskets. Lots of miles. I wouldn't get worried about it until you have problems....but if you're having problems, then yeah, copper gaskets and O rings is the usual solution, but coolant sealing can be an issue with those
I'll second the stock gasket at 6-7# of boost. I ran a 8.8:1 engine at 8# for 115K mi on factory gaskets. I like FelPro & Victor aftermarket gaskets. In my application, FelPro's were .060" and Victor's were .045". You could play with compression and clearance a little. We ran a Victor on a 10:1 engine and 13# on the dyno. Head gasket was not an issue. Mike
Use stock FelPro head gaskets on my 392 Hemi.....Makes about 10LBS of boost and have over 7000 miles on it and no issues....Used headstuds torqued to 100 FT LBS...
Yep, one more vote for stock head gaskets with that kind of boost. Working on an 871 blown bbc now that only makes that kind of boost and stock head gaskets have worked fine for 20 years.
Stock, Fel-Pro, or Best. If you can get head studs, use them. If not use fresh, high-quality (ARP) head bolts.
Thanks all. It sounds like stock head gaskets are fine, at least up to 10 lbs. Built lots of engines but this is the first blown one so going through the learning curve. So another question, cast pistons OK at that boost or are forged the only way to go?
Never took the chance with cast pistons to find out. That seemed like an expensive mistake to avoid. I have two turbocharged engines, and a supercharged engine. All have forged pistons, and an all steel bottom end One turbo engine runs 30psi.
I'd look at it like this.......... How many types of head gaskets are available for a 365 Cadillac? Not Many What is the surest way to make it work with no problem? O-ring If I do have a head gasket problem at absolutely the worst time........will getting my car back home and fixing it cost me more than O-ringing would have cost ? As for the pistons, hypereutectic at the minimum. Forged is best. New factory supercharged engines run hypereutectic, but they have knock sensors which immediately retard timing if there is a knock. You won't have that protection. Usually it comes down to money.......and the question is: Why is there always enough money to redo something but not enough to do it right the first time? I know thats how it is with me anyway.
Stock Felpro on a blown 354 Hemi here only 3000 miles so far this year no problems. Ran the same on a small block Chevy for years again no issues. Way back ran a Ford 3 litre Es*** V6 with a Wade blower making 15 lbs on stock Ford gaskets .
Head gasket sealing is all about clamp load, especially in boosted applications where the cylinder combustion pressure is working hard to lift the head off the block. So make sure you use either new bolts, or preferably high quality head studs and make sure things are torqued properly.
It all depends on the application . Many years ago a guy here had a 6/71 on a big block Mopar,,,,,,it had a stock bottom end and never gave any trouble,,,,,,so I know it can be done . He had a Streetcharger unit from Dyers,,,,,I’m ***uming about 8 psi or so. BDS used to list about 5 pounds safe for cast pistons,,,,,so I guess how lucky do you feel . Also,,,,,,all cast pistons are not created equal,,,,,some are better than others . I would think in a moderate application,,,,,mostly street cruising,,,,,it would be perfectly safe . The Achilles heel of most cast pistons is bore clearance,,,,,,the more the pistons rock,,,,,the skirts smack the walls pretty hard,,,,,,,that will break a cast piston . If you are heavy with the pedal ,,,,or gonna be on the heavy boost a lot,,,,,I think forged are best . Tommy
Ganahl's book Street supercharging covers this stuff. Cast pistons, it depends on how you drive the thing and avoiding detonation. I ran a smogger 454 at 6 lbs up over 6,000 rpm regularly for a couple summers with no issues, but I always used adequate fuel. If you just cruise around and nail it once in awhile, cast can live. You gotta have a solid flow of fuel under load.
No matter how you rationalize it, building any motor will consume a sizable chunk of change if you do it properly. The old saying "a chain is only as strong as its weakest link" applies here. I'd use the stonger links...........
Cost difference of cast to forged pistons divided by the number of years of expected use = cost per year for the insurance of forged pistons. There's your justification. Edit: I haven't seen anyone mention this. When a cast piston goes bad they have a tendency to shatter, leaving the pin and rod free to inflict fatal damage. With a forged piston, the piston won't shatter. Maybe a hole or broken ring land. Likely can get away with just replacing the bad piston instead of possibly the entire engine.
If you are gonna run a supercharger, I'd look at what rings you need to use and how big or little the gap needs to be.
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