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

William wrote:
> 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

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.

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


"William" > wrote in message
...
> 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

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:
> 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
>
>
> "William" > wrote in message
> ...
>
>>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
>
>
>

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