MotorHead

My deck height on newly machined 406 ci block is 9.025in ( standard ) and O deck is 9.0 in ( I think that is correct ). I want a head gasket that will put in the 0.040 - 0.050 in quench area so I need a gasket that is about 0.020 compressed.

Oringinally I was going to use a steel shim head gasket but I am worried about all the different metals I will have ( iron block, steel gasket and aluminum heads ) and the different expansion rates.

Anyone know anything about this or for that matter if I use the regular Flepro composite gasket then that is 0.039 and puts my quench area about 0.065 in. Is that a problem ?

Pistons ( SpeedPro flat tops ) I have are 10.8 :1 at the standard deck hieght with standard gasket ( 0.039 in for SBC ) this is my understanding of how most piston manufactures advertise their compression ratios.

turtlevette

chev high performance used a rubber coated steel shim gasket on their project to keep compression up. The aluminum heads can't be used with steel shim but the coated ones are supposedly ok.

Desertvette

Had the same problem with my 327 with aluminum heads. Needed a .020 gasket to maintain proper quinch.
I used SCE copper gaskets with Permatex copper spray both sides. You should also use bonding straps between the heads and block 2 places each head and a sacrificial anode in your radiator neck to prevent electrolysis corrosion along with Zerex G05 anti freeze. I wont use Dexcool since having a bad experiece with it in a 98 Blazer. but thats up to you
The SCE copper gaskets are available from Summit and are a little pricey but I've had no leaks and they are reuseable if you have to disassemble for some reason. The sacrificial anodes can be found a JC whitney or even Ebay where I found the one I bought. LOL
Bob

VETDRMS

I would get ahold of Cometic Gaskets. They can make you a custom gasket to your specified requirements. Make sure you get steamholes. They run ~$150, but I would shy away from running .065" quench. Keep it from .038-.048". "Factory" compression ratios are usually determined with a zero deck, .039" gasket (or so) and 64cc chambers. I would use a simple compression ratio calculator to get an ~exact number. With that longer stroke your going to build a fair amount of extra pressure. All things being equal (head gasket thickness, deck, compustion chamber), a 406 will have a higher compression ration than a 350. That 427 will be putting the squeeze on... :cheers:

cardo0

The target spacing for good quench is less than .045" between piston and head. If your running zero deck and flat-top pistons that measure even with deck hieght this should give you excellent quench with the 0.038" compressed hieght of a composite. But measure your piston to deck hieght first. David Vizard (the wizard) writes the danger zone is about 0.022" quench hieght were the piston my slap the head. He also says good quench is worth about 8-10 hp. But other benifits are the better fuel mix reduces detonation and allows higher compression for pump fuel. Also better mpg.
I recall you posted installing studs and this makes sense for using copper gaskets. Copper head gaskets allow for very fast head R&R if installed dry (no sealer). I just have never heard of the sacrificial anode idea on head gaskets though seems to make sense and kinda like it.
I called Felpro (years ago) and they said okay for aluminum heads using thier rubber coated steel shim but I still have my doubts. And with higher horsepower you can expect more stress on the gaskets. But this would put your pistons where they might hit the heads.
My vote is for either copper or composite but leave the steel shim alone (just for your set-up thought as I am using them on a stock hieght block and iron heads).
Ditto for the steam holes.
Good luck. :D


[Modified by cardo0, 2:02 PM 1/31/2004]