Hey guys, what size dished pistons will produce an 11.5 to 12:1 compression ratio.I'm thinking somewhere around 5cc but I'm not sure.Any help would be greatly appreciated. This is for a 99 GT 2v.

 

5cc will giva ya right at 11.25:1

 

It depends on what brand piston you go with. For example: A 15cc Diamond piston produces the same compression ratio as about a 17cc Manley piston. Scott from VT engines told me this. Manley claims there flat top piston makes a 10.5 compression ratio, so you would have to go with a pop top piston from them to get that ratio.

 

There are some small variances in tolerances, and one company may be machining their pistons on the small side, and the other on the big side.While a 2cc variant would be alot, it is within the OEM spec'd tolerance. But, the only way to estimate the c/r is to use nominal numbers. If Manley advertises a 17 cc volume, then that's what you have to use in your calculations.

That being said, you'll want to go with something like a 1.8 cc to put you in the range you've defined. An aftermarket flat-top will net you a bit over 12:1.

Don't mess around with head gasket thicknesses. Leave them of stock thickness. I'd recommend you use an OEM gasket anyway. 4C2Z-'s are what you want.

 

call JE and theyll make you some your looking at domed pistons though

 

Hey thanks alot guys.Im still not sure if i want to go N/A or turbo but I'm trying to add everything up to see how much each will cost.

 

Well, you'd better make up your mind before you select a piston, 'cause you won't be able to run 11.5:1 to 12:1 c/r with a turbo.

David_K, why would he want a 'domed' piston? He can achieve 12:1 with a flat or near flat piston.

 

01Steed, why do you think a flat top manley will put him at 12:1? Manley told me that a flat top would put you at 10.5:1 so it would take a dome piston to make 12:1.

 

We're talking about 2V's here, not 4V. Flat tops in a 4V will net approx. 10:1-10.5:1.

 

Your right, 4v has a much bigger combustion chamber.