What is the stock head gasket thickness? I would like to lower my compression for a SC (in the future obviously) and want to know how low I can get my compression if all I change are the head gaskets. Is it possible to get the compression below 10:1 just by changing the gaskets?

ShibbyZ

 

Stock aluminum head gaskets are .049 already pretty damn thick and doing nothing good for quench.
The stock iron heads are good for 10:1 with their stock roughly 64cc chambers and .029 gasket.
IMO I see three ways to reasonably achieve 10:1 one iron heads with .029 gasket I am sure not something you want to hear but they flow more stock than your 94 aluminums so don't dismiss them just yet.
TrickFlows are a 64cc chamber and then maybe use the .026 Mr. Gasket head gaskets will get you slightly more than 10:1 but will seal etter with the aluminum than the ones meant for iron heads.
Third swap the pistons.

 

Iron heads? I thought they were aluminum?

Wayne

 

What is the stock alluminum cumbustion chamber size? I read somewhere it was 55cc. I also plan on porting the heads once they come off to get new gaskets. So I might lose a few cc there, but yeah nothing huge. The reason I want 10 or lower is for the supercharger. I do not have the money to rebuild the bottom end or buy new pistons to lower the compression, so head gasket thickness is my only resort. Here is basically my plan if anyone really cares.

-Stock or CC305 cam (haven't decided)
-987 springs or LT4 springs (depending on the cam)
-1.7 scorpion roller rockers

So that will set me at about .506 and .520 lift on a stock cam. Then I plan on 6psi boost on the supercharger. Since I was going to port the heads to help the SC, I thought I might as well change to a thicker head gasket to lower the compression to help prevent detonation atleast somewhat. Does any of that sound good?

 

The stock chamber size is 54 CCs. You can run 6 lbs non-intercooled boost without issuse on a stock set-up (with a good PCM tune). Do not go with a thincker gasket, as that will raise your quench and potential for detonation.

Get a blower specific custom ground cam, it'll pay more dividends in the HP areana and only costs around $50ish more. I got mine through MOre performance, but there are a few folks on this board (Bret Bauer) who come highly recommended as cam profilers.

The aluminum heads are more forgiving in the detonation area (your most critical factor with boost). If you dont' have the funds, keep the boost low, pay for a GOOD PCM tune and start saving for a forged bottom end.

 

Look at his screen name... he was refering to the stock "Impala/Caprice" cast iron heads.

 

I don't think a stock LT1 and boost is great idea. I have seen too many broken pistons. To make it last, you need to limit the boost to 6psi and a stock headed LT1 doesn't gain that much from 6psi. For whatever reason, stock LS1 motors seem to last longer. And they make large amounts of hp with just 6psi, so it is worth it.

Rich

 

So 6psi is where I should be at. How long would it last roughly if I just threw the SC on there with nothing else done? I know a lot of people don't like this question because it is a hit or miss thing, but there should be atleast an average right?

Injuneer, using the equation you helped me with in advanced tech, 6 psi would set me just above 400fwhp. Just wondering, but what is concidered "responding well" to a SC? I would think 6psi from 280fwhp to 415fwhp is responding pretty well. Atleast well enough for me.

 

I would find 415 bone stock + sc hard to believe... With mods yes. Not stock and 6psi. * Edit, oh FW.... maybe 400 fwhp.

Do it right. For what the blower is going to cost you you can build a very nice na motor to make the same power. Drop some dish pistons in and add a sc if you can afford it.

 

Just playing with numbers, (14.7 + 6.0) / 14.7 = 1.408

1.408 X 280 = 394 flywheelHP.

But some of the HP is eaten up powering th S/C, and air mass flow is not what you would expect because of the heat of compression, at least without an intercooler. You'd be lucky to see 375-380 flywheel.

 

Back when I first installed by 6# Vortech on the stock engine with JBA 1 5/8" shorties, I dynoed 370 rwhp with a M6.

 

The headers make ~20-40rwhp on a blower car. Stock LT1's with 6psi are in the 350-360rwhp range. IOW, they gain ~85rwhp. They can last if you run them rich and retard the timing a bit to avoid detonation. With water injection, mine lasted for 2 years and ~12,000m, until I decided to up the boost to 10psi, at that level it lasted ~75 miles.

Rich

 

I think that if your gonna do it at all. Do it right. Dont take any short cuts or else it might end up costing you in the end.

 

I took a lot of shortcuts and it is catching up to me. I would not cheap out on a blower setup though...

 

Solid advice; however, very few people have the funds to go full boogie. There is always soemthing else that "needs replaced" or needs upgraded". Just set your budget (and end up doubling it) and keep your expectations conservative.