It has been quite a while since I have posted but I am hoping for some information on thinner headgaskets for the LN3 engine. I would like to tighten the quench, piston to head, clearance. Stock gaskets, the same as Victor Reinz, or the Fel-Pro are both in the .060" compressed thickness range. I am looking for something in the .035"-.040 compressed thickness gaskets. I already have zero deck pistons and am looking to tighten things to help knock resistance. I could have the block cut down but the block is nice and square and flat now. There are selections of different gaskets for the older 3.8'* and the newer Series II'* but nothing for the orphan LN3. Any leads appreciated

Did I gather that right? You want to increase compression to reduce knock?

yep, wrong way, increased compression increases knock. you need to look into your tune if you are getting spark knock

You understood correctly. This engine already has L27 pistons to get the zero deck but the .058" squish is in a sort of danger zone for being lightly boosted, hence the knock. In theory, tightening the squish should help with that. Nothing is definite of course, and it will likely get Singh grooves at the same time. It does not knock if operated in N/A mode. I can have the block decked the appropriate amount, but I dislike possibly making a mess of what is now a nice flat and square block. The resulting compression ratio should be in the 9.1-9.2:1 range. It'* a spare engine, so experimenting to prove the theory will be interesting.

I think your mislead. Anytime air is compressed, it creates heat. Anytime you create more compressed air via turbo, supercharger or cylinder dynamics you increase the chances of knock or pre-detonation.

Forced induction - Wikipedia, the free encyclopedia

And because you are increasing your compression ratio from probably 8.5:1 to 9.1:1 you are increasing cylinder air pressure which increases temperature.

So in theory, by "tightening" this squish, you are only increasing compression.

I do understand the ramifications of tightening the squish band clearance. Compression ratio will increase a bit more that I have now. I am trying to increase mixture motion with this change. In stock LN3 configuration, piston to head clearance is in the .100" range, or not much squish at all. The compression ratio will be slightly more than a '93 L27. I must believe that no one knows of a thinner gasket?

Problem is, its a grandma engine. You probably won't find much performance addons besides bolt on stuff, and even then your having problems finding that stuff.

You could try these guys.
Cometic Custom Gaskets

Yes, I know what you mean. Many years ago when I started fooling with it, I found there was little available, and actually had one vendor say "why bother". I'm not looking for a rocket ship, just a little more, plus I enjoy experimenting. I have two completely different turbocharger installations, one very low boost (4 psi) using only the front manifold that requires very little fabrication and even runs on the stock chip. The other is more mainstream and 8-10 psi boost, but that one wasn't intercooled, and had some issues with boost control. I think I have that worked out now but the one area I want to verify is the theory of tight squish helping knock. The thinner gasket would be the easiest solution without a permanent modification to the block. I came here because the Pontiac guys have been more performance oriented over the years, and my Buick forums are more preservation oriented.

Thanks for the tip on Cometic. They are on my list although they don't even list stock gaskets for the LN3. We shall see.

Yea, I'm a tinkerer too. Who cares about looks right? All about functionality!


I'm surprised that company doesn't say send in a brand new set of gaskets and we will match them to your thickness specs.

still think you got it mixed up, knock is pre-detination, from burning fuel before its time which is made worse by compression. on non boosted engines you can give the engine more cr and make more power because it draws in less fuel/air than it can "handle". but boosted engines want as much air space as possible because the mix is pushed in as much as the engine can handle. your fueling and timing have more to do with knock, so thats why i said you have to tune it