Hey guys, Ive finally saved up enough money to complete my NA build. Right now Im looking into parts to raise the CR. Ive 'heard' that installing OEM AP1 JDM pistons in an AP2 raises you CR significantly. Is this true? If it is not, what would you recommend for me to accomplish this? Im installing TODA specC cams and want some more compression to compensate for the higher duration on the low cam.
Thanks!

 

I think you would be better off getting a set of rods/ pistons from a company like Toda or some equivalent than going the OEM JDM way. The JDM cars have the higher compression ratio due to the higher octane of fuel available over seas.

 

Ever thought of stroking the car out?

 

might as well get a turbo kit and sell all my NA parts for the cost of the stroker. Im not that tied to NA. Im just looking for a lower cost alternative to raising the CR.

 

Spoon headgasket raises the CR by 0.2.

Cheap product, $$$$ labor.

 

get the head milled

 

the problem is that Ive heard that the Toda cams require a good amount of valve relief. If I were to mill the head or put a really thin head gasket I might have valve clearance issues.

 

I have to install valve springs anyways so putting a different headgasket wouldn't change the labor thankfully. But the spoon gasket is way over priced. Ill just get a cometic that is the same thickness. .030 inches IIRC

 

^ Several people running boost have had problems with Cometic head gaskets. These were 2mm and 3mm gasket spacers, but I don't know if their regular head gaskets also have a history of problems, just giving you a heads up. The only way to increase CR aside from getting new pistons unfortunately sacrifices valve clearance. With cams, I'm not too sure that's a good idea.

 

Has toda fixed the problem with their cams snapping in half? I've heard it happened to a few people before and haven't heard if they've changed the material to fix this or not? I'm trying to look into some cams for my engine build pretty soon and I am waiting for results of a few different applications.