What combo for turbo?

Ive already got the vic jr heads.. 75cc..

Ive got a couple diff options looks like

6.7 rod.. 33.3 dish pistons.. 75cc heads.. .60 head gasket 9.2ish

or 6.8 rods.. 33.3 dish pistons.. work heads to 86cc.. .40 gasket 9.48cr

or 6.8 rods.. 33.3 dish pistons... 86cc heads.... .60 gasket 9.1cr

or .70 gasket 8.9 cr

So looks like I'll prob end up with 6.7 rods and 33.3 pistons cuz I can keep the 6.8 rods and flat top pistons and easily put all back to the 13.7cr setup.. Not so cheap to put the metal back on the heads.. lol.. Also I could just sell the rods and pistons and replace some of the money spent.. Either way.. I think this option is the choice for me.

HamBone said:

So Im looking into building a turbo bbf.. currently i have a 545 bbf.. 4.5 stroke 6.8 rods.. .30 over flat top pistons.. 13.7 compression ratio through a .39 gaskets

Im not sure about my options for lowering the compression though.. could I just switch to a 6.7 rod and get a lower compression.. I know the 6.7 would lower it but how much is the question.

I want the motor to be 9.0-1.. I can deal with anything for 8.5-10.0 though.. Thanks for any help

Click to expand...

If your compression is a true 13.7 to 1, then installing a 6.7 rod will get the compression to 10.8 to 1 using your existing pistons with a 1.25 compression height.

Installing a 1.25 compression height piston with a -33.3 cc dish with your existing rods will give you 10.5 to 1 compression.

Installing a 1.25 compression height piston with a -33.3 cc dish with your existing rods and a .060 thick head gasket will give you 10 to 1 compression.

Installing a 1.25 compression height piston with a -33.3 dish with 6.7 rod will give you 8.7 to 1 compression.


To get exactly 9 to 1:

Install 1.25 compression height piston with a -33.3 dish with your existing rods and a .120 thick head gasket. Others will have to chime in if the head gasket will hold with so much of it exposed. I'm talking about a Cosmetic Gasket.

What shelf pistons where you planning on using, or are you planning on getting custom ones?

IMHO, it would be better for you to start from scratch if you're wanting a turbo motor. 600-700 hp is no problem with your current set-up done right, 10.5 to 1 compression, and be streetable. If you're wanting a turbo on top of that, 1,000 to 1,500 hp is going to be a mild turbo build, but you should be using good parts.

Do all your research, including the size turbos it is going to take, then figure how you're going to get all that under the hood.

Hope that helps,

Dave