What are the different effects of raising compression by piston and raising compression by thinner headgasket?

I'm thinking of running 12:1, and by going through the calc at c-speed, it seems that CTR pistons and a Toda 0.6 headgasket should put me at about 12.1. Through searching I also found a snippet about the Endyn 12:1 rollerwave pistons.

And also, how would ITR cams respond to this jump in CR after tuning?

 

I have a question to add...
if you don't mind.
If ya put a thinner head gasket in a "stock" R would it do anything worthy?

While on the topic of headgaskets
Thanks!

 

yes, it would bump up the compression.

 

thinner headgasket raises comp

 

i have a moogen headgasket (well its actually made by rota)

 

The C-speed cr calculation says that a B18c5 (block/head) would have a cr of 11.5 with Jdm Itr pistons. Is that accurate? I thought the Jdm R is at 11.1 difference being only the cc of the piston?

I also want to raise my cr to hopefully compliment the skunk cams, but I havent heard any good news about using a 1/2 layer head gasket reliability wise. If I had the money I would just swap pistons and use a stock head gasket.

 

what reliability issues are you talking about?

i beleive the JDM R was 11:6 and the USDM R was 11.1 in the earlier years(before 2000/01). I might be wrong on this.

 

USDM R has always been 10.6:1.

JDM R pistons will yield 11:1 CR with 87.2mm stroke and 42.7cc combustion chambers (like what you'd find in a B18C5).

The question is how much do you want to raise your compression. A thinner headgasket can only give a few tenths of a point, and it does reduce valve/piston clearance (by a fraction of a millimeter). On the other hand, it is a hell of a lot cheaper to replace a headgasket than it is to change pistons.

Another way to look at it though is that you should replace the headgasket any time you remove the head, which you would do when replacing pistons, so you could use stock JDM-R pistons and an aftermarket headgasket to get around 11.3~11.5:1 CR.

 

My Gsr motor had Us itr pistons with a .040 mill. I'm thinking the cr of that motor was around 11.2-3. It was pinging a lot. I had to retard timing to 12 for some reason, while most here are running 12.1 on 91 octane and stock timing. The reason I didnt like shaving the head was because you cant go back on that, plus my timing belt covers wouldnt fit anymore (just in case I had to ref the car).

I'd go with Jdm R pistons, or an aftermarket forged that would give you 11.5 cr and an oem gasket for reliability issues.