Supercharger on 5.0 "GT" engine

I have the crate GT-40 engine in my '88 notch back coupe along with other goodies (MAC shorties, BBK cats, aluminum driveshaft, Auburn 3.83, 32 spline axles, 4-wheel disk brakes, etc.). I'd like to know if I should O- ring the heads prior to installing a (approx) 14LB boost supercharger.

Mr. Bill

Reply to
William
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I have run up to 16 psi of boost on my '89 LX. The max I would recommend is 12 psi. Mine could blow head gaskets at that boost level with just the slightest bit of detonation. IMO the 7/16" head bolts aren't up to the task of keeping the heads clamped tight enough to the block under high boost levels. Also, you really need to have forged pistons (I believe the crate engines have hypers) for that much cylinder pressure. If your crate motor has an 8.5:1 compression ratio or less then it would be much better able to handle the higher boost.

As for O-ringing the heads I have heard two schools of thought. First is the O-ringing does provide a better seal and can save a blown head gasket. The second is it might force a more destructive failure (i.e bent rods, cracked piston etc.) than a blown head gasket. I guess you need to pick you poison. Personally, I wouldn't O-ring unless I had a race block with a forged, top notch rotating assembly using 1/2" head studs.

After traveling down the supercharged road for several years I learned one valuable lesson... the best way to make horsepower with a blower is by increasing air flow by porting etc. than by raising boost. I ran stock GT-40X heads/Cobra lower intake on my Kenne Bell blown engine and made good power. I then had the heads ported with a three-angle valve job and the lower really hogged out and made more power with 12 psi of boost. The benefit is the intake air charge was much cooler and I could run a more aggressive tune in addition to moving air more efficiently into and out of the engine. Be careful though, because if you plan to use a centrifugal blower too much porting can make the engine a dog in the lower/mid rpm range. Since I have a Kenne Bell blower this was not a problem.

Reply to
Michael Johnson, PE

How well maintained is the vehicle? How many miles? Have the heads been P&P? Have they been milled at all? Do you know what your compression ratio is? If you are sitting at 9:1 with under 50k miles I wouldn't O-Ring it. If you have 10:1 and a lot miles I would.

Don Manning

Reply to
2.3Sleeper

If he has a 10:1 CR and runs 14 psi of boost he had better weld the heads to the block. :)

2.3Sleeper wrote:
Reply to
Michael Johnson, PE

Thanks for all the advice. It will not go unheeded. William

Reply to
Mr.Bill

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