Raising Compression Ratio

Change pistons.

Manny

Shaving the head would also do raise the c/r.

but what piston ?
i dont know how to calclulate it
even stock add 1.2mm metal gasket i no idea what is the new compression

Call JWT, they will tell you what pistons to buy.

he's in malaysia, might be a pricey phone call I'm sure you can search for it somewhere.

I thought adding a thicker metal headgasket would result in LOWERING the compression.

cmng said:

but what piston ?
i dont know how to calclulate it
even stock add 1.2mm metal gasket i no idea what is the new compression

Click to expand...

300ZX normally aspirated.
You will need to trim a bit from the bottom of he piston skirt (like 1mm) but it will get you 11:1 compression.

If they arew available there post here for more info on what is needed.

Chris

300zx NA piston
cut down 1 mm.

11.1 .
is that good compression for NA based GTiR block ?

It will not be 11:1 in a GTIR. The GTIR has a different cylinder head CC, therefor it will be less than 11:1. I dont know what Z32's will make it. somewhere between 10.5 and 10.8:1 id guess.

Remember that the GTi-R combustion chamber holds more volume than the other DE's, DET's. Because of this regular caluclations will be about 0.2 points off. For instance the 300zx pistons will only give a 10.8:1 CR (from my calculations)

With the 1.2mm head gasket your compression ratio should be 8.4:1 CR. If you get a Tomei 1mm head gasket and the 300zx pistons that should net you an 11.1:1 CR. You could always get some

Wiseco makes some 11:1 CR pistons for the DE. This would yeild a 10.9:1 CR in the GTi-R motor. With the Tomei 1mm head gasket you would get 11.2:1

Not worth it for that extra 0.1 points but the option is out there to use forged DE pistons, they will need to be machined to clear the oil squirters.