Still a little new to these forums but i tried doing a search...

Back when i had my supra...it was a non turbo model so i used a 3.0 mm gasket to lower the compression ratio...my question is has anyone done this to a Z??? i read a few articles from turbo magazine a while back and a few other FAQs about this and it sounds like it hasn't been done...at least not announced...

 

It is not that simple to change the head gasket on this platform, the engine basically has to come out, not as easy as change the head gasket on a supra or evo.

It's a big job, when you could just run less timing/boost and achieve the same result.

-George
GT Motorsports

 

yah i guess you got a point there...i guess also since the engine is out...mid as well just tear it down and build the bottom end or something

 

because of the design of the engine you need to use the stock spec HG's. or else your timing chain cover bolts will not align. and there will be leaks.

 

I know what your trying to say with the relation to cylinder pressure but by no means is it the same. I mean no disrespect by this but running less timing dose not lower static compression, running less boost would have an affect on dynamic compression but also would mean less power. Theres no denying that as far as pump gas is concerned, low compression(static) mixed with big duration( affecting dynamic) would rein supreme as far as knock threshold is concerned.


That being said, I agree that I would never do it to a stock motor. Not only is it not worth the effort but you'll exceed the TQ limitations of the rods before you exceed the knock threshold of the combustion chamber.

 

even if u lower the CR, how much power can the stock internals handle ??
the rods are the weakest point right ? correct me if i'm wrong...

 

Exactly. A thicker head gasket will work on an NA supra because the stock internals can handle some power and you just need to get the CR down. On a 350Z, the compression ratio is not the problem on a stock motor - the rods are. And if you are going to put rods in, do it proper and use lower compression pistons and then you have no need for 'thicker headgasket'.

 

the only way to properly use a thicker head gasket on these motors is for adding back some height that was taken away from head/block decking.

 

I was being general, you can lower the compression to raise the knock threshold, or you could run a less aggressive tune, both would result in roughly the same power output - in which case the latter would be the easiest (and less expensive) option.

No disrespect taken from your post