Building a 3.4 PR, pistons/compression questions

[JustinParcher]

Hello all, I'm in the process of assembling parts for a 3.4L PR motor I'm putting together. I've got everything waiting except for the pistons, which have been backordered for two months now. I originally decided on getting '96-'97 DOHC pistons, as they raise the compression over stock iron head pistons.

However, I have since learned that apparently the design difference between their earlier ('91-'95) DOHC pistons and the later ('96-'97) pistons is such that the earlier design makes higher compression when compared using the same head design. Is this true? I thought (apparently naively) that since the later design had a larger listed compression distance, it would net me more compression, but in reading this article it states that the opposite is true.

The specs for the pistons I ordered show that they have a 1.464" compression distance, with a .040" dome, and four valve reliefs cut in them. The earlier pistons are shows as having a 1.458" compression distance, and no dome. Am I losing my mind, or would the newer pistons actually have a higher compression ratio?

I'm shooting for roughly 10:1+ compression, using the stock .040 gasket. Since I don't have them yet, I can still change to get the right pistons.

Any help from someone who knows what they're talking about would be GREATLY appreciated.

[bob442]

First off what gen heads are you using?

[JustinParcher]

Stock iron Camaro heads.

[JustinParcher]

Bump. Anybody?

[bszopi]

Try plugging numbers into the site's CR calc here: http://60degreev6.com/content.php/101-CR-Calc

Unfortunately, I don't have the 96-97 piston info in there, but you it will give you everything else you need to figure out what CR you will end up with various components.

Here is a good article describing how to best utilize the calc as well: http://60degreev6.com/content.php/20...-CR-Calculator

[JustinParcher]

Thanks for the reply. I have already done that with the early pistons, which says it should be 9.95:1. However, without the info for the later pistons, I'm not sure. I just don't want to go to all this trouble buying later LQ1 pistons if they're actually gonna be lower compression than the earlier ones, since I'd really like to get 10:1 or better. For comparison, a piston with no dish volume would be 10.73:1 which would be great as far as I'm concerned. Guess I'll just wait out the later pistons and try to take some measurements.

[JustinParcher]

I'm going to explore other options anyway, as the pistons I ordered got pushed back on their delivery date AGAIN.

My question is this: what's the easiest way to get at least 10:1 compression on a 3.4PR with stock heads? I found flat top pistons, but they're for a 3400, which I believe would result in interference, correct?

Still Looking for some help here, I just need advice now.