Ok I did a search but couldnt find anything on this .....

Back when I had my IS300, people where running ticker headgaskets to reduce compression on the motor so they could boost more.

Now my question is are people doing this on the Z just to reduce compression and protect their motors from poping ?????

If this has already been discussed can someone direct me to where I can find the info. Thanks.

 

No one has this out for the Z yet...

However it's not the best way of lowering the compression ratio. Because it upsets the "squish volume" around the rim of the chamber. This will increase the likelyhood of getting knock even if you lower the compression ratio.

I know it has been done before it's just the wrong way to do it.
Gary

 

That makes sense ... but a lot of IS300 guys where success full with it. Is theat do to its a 2JZ-GE ... stonger block and such?

 

To add to this...the time and money spent...would be better off saved and waited till you had enough to do piston , rods , any anything else needed to up the boost and make it safer

 

It works at helping stopping knock but you have to reduce the compression more that way to achive the same results as say using dished pistons.

The excessive loss of low end power and response is what makes it less attractive than doing it the right way. Because you could do it with pistions and only lower it a point or so. But to get the same results with the thicker gasket you's have to lower it by say two points.

Also Booger is right since you can get to the strength limit of this motor without lowering compression it's not worth it any way you look at it.
Gary

 

This works great on inline motors but not an easy thing to do on a V engine. If you run thicker headgaskets, you physicall move the heads up and therefore farther away from each other as they move up the imaginary V. This causes problems because the lower half of the intake is shaped to fit the factory spread of the two heads. Start messing with that and the intake won't line up and seal to the heads. The bolt holes will also not line up that mount the lower intake to the heads.

 

Yes Cometics is coming out with thicker headgaskets than stock, not by choice but their thinnest gasket is still quite a bit thicker than stock. 7-eleven is right this is not the correct way of lowering compression. You can also get into problems with valve timing when putting increased distance between the heads and block.

 

ojokokokokok


what is knock, for the last time.

please someone enlighten me

 

"knock" is the sound made by in cylinder "detonation". Do a search on detonation , you'll find lots.

 

Good info guys thanks makes sense now.

 

Quick question guys if I had a guy pull my heads couldnt he lower my compression through porting them and at the same time get the heads to flow better so that I would still be gaining more hp and lowering the compression so that I could run a little bit higher boost levels? Just curious .

 

porting generally doesn't lower the static CR, it just inproves the flow characteristics in the intake and'or exhaust runners (pre-valve). Altering the OEM combustion chamber (post valve) to lower CR is not recommended and could totally F-up the anti-detonation effects provided by the carefully designed chambers. The only reliable way to lower CR on this engine is with dished pistons.

 

A couple of more questions for you since you seem to know.
If I put better pistons in and leave the heads alone and lowered the compression down would I then be able to run around 14 psi pretty safely or would I have to change the rods as well.Because ROds seem to be 1,000 and this just keeps getting more and more expensive.

 

The rods seem to be the weakest link.....yes you will need rods

 

As booger said , to date the rods appear to be the weakest link.
If you rebuild the short block ,forged rods are worth their weght in gold. The price of rods will come down over the next year or so as more "value oriented" manufacturers such as Eagle get into the market.