Just Wondering...

I was just wondering what kind of effect forced induction would have on that plastic intake manifold gasket. I remember when I replaced it that the torque specs for the mouting bolts seemed really low, and it seems like forced induction might cause a blow-out. any input??


Thanks,
Paul V.

[BlackJack]

since you have a 3400, I'd recommend you check with germ on that one. I believe he has identified a composite gasket material that works well under reasonable amounts of boost, as well as strengthened stud sets. As for higher boost levels, my recommendation is forged pistons and "O-ring" the deck.

head gaskets are the weak point on the engine as far as forced induction goes.

the lower intake gaskets are fine for boost and i have had ZERO issues with the lowers and i have actually re used the lower intake gaskets when i had a head gasket failure.

as for the head gaskets, you will want to use a graphite based gasket at a minimum. do NOT use Felpro

this is my recomendations for manufactures for head gaskets that seem to last under boost for the 3400....


1. stock GM replacements and make sure you get the NEWEST part number and NOT old stock.

2. Corteco gaskets have a special coating (not graphite, but some sort of silcone base) and seal very well.

3. Victor Rentz gaskets (can be found at Napa). Victor Rentz gaskets make GM replacement gaskets FYI

4. Rol gaskets are graphite based, but i have never used them.


now for the lower intake gaskets, pretty much all the new ones are stronger than the old stock gaskets, but here are my recomendations for lower intake gaskets...

1. Stock GM replacements, they have the disc's on the side of the bolt holes on the end to avoid over torque

2. Victor Rentz gaskets. same as the stock GM gaskets.

3. Felpro, no metal disc's, but i have used them on my boosted 3400 from the beginning and i have actually reused them a couple times. i am puting on the victor rentz gaskets tomorrow FYI

4. Corteco, never used them, but heard good things about them.


hope that helps

now for the reason why the lower intakes last longer than a head gasket....

lower intake will ONLY see you max PSI your turbo/supercharger pushes, so if you run 12psi, thats the max it see's.


the head gaskets on the other hand have a MUCH, MUCH higer psi level in the combustion chamber when the fuel is ignited, no add that 12 psi on top of that, and your talking a VERY VERY high amount of pressure applied to the rings of the head gasket.

no add in the constant explosion of fuel plus the effects of oil and coolant on the head gasket and you can see why the head gasket fails more easily than the lower intake.

Cool, thanks for the input. Now, are the head gaskets on these cars a common problem without forced induction? As I was browsing through the forums I notice head gaskets coming up quite a bit. Is it something I should be concerned about? And, if so, how does it compare to the 2.2l OHV motors that were notorious for head gasket leaks?

for the most part, the head gaskets are ok. of course there are failures with them, there always will be. no one has a 100% non failure rate. a LOT of times, the head gaskets is mis diagnosed and is usally the lower intake gasket.

HOWEVER, if you have a LOT of miles or the car is very old, then i would consider replacing them.

age and mileage will play a toll on any part.