JDM 007

I've done a whole lot of searches and could not find anything to do with JE 9:1 pistons and what compression ratio it yields. Is it as simple as it looks, being 9:1 or will it be higher on a B18c5.
The reason I ask is I want to know if I get pistons/rods is it worth getting a thicker head gasket?
Can anybody lend some knowledge on this?

Thanks

ricodemus

I think most of the time the 9:1 is for the pr3 head (b16 and type r). It will yield higher compression with the gsr or ls head. I wouldn't want to lower it any more than 9:1, but what do I know.

JDM 007

I totally agree, that is why I need to know the exact compression ratio a 9:1 piston will yield on a B18C5. If it does lower it to that number, obviously a head gasket would be useless.
Anybody with a Turbo ITR have any info on this?

highbrid

well if you have pistons that are made for a type r and they say they are 9:1 cr pistons they should yield that cr. This is assuming that your head hasnt been milled etc....

true

I think you are asking what b18c 9:1's will yield in a b18c5? It will be about 8.9:1. IF you don't mill the head or deck which you probably will. .1 or .2 won't make a bit of difference to you. I wanted 9:1 in my 84.5mm b18c5. I ordered custom pistons and ended up getting a shelf b20b4 84.5mm 9:1. I was concerned as I knew the b20 stroke is greater...after I did the math it came out to be 8.84:1. This is BEFORE my mill, and deck..which will put it back up basically to 9:1. Noone can tell the difference between a tenth or 2 of a point.

So for future reference....if you want to get ~9:1 84.5mm in a gsr/typer you can use JE shelf pistons. This is cheaper.....and if I hurt one pistons, I don't have to make a custom set again.