Say I do keep the P1 headunit, will I need to raise that 8.3:1 C/R up to get the most out of it. Can I use a head gasket or am I going to be milling the heads a little? I know theres someone out there that knows.

 

8:3 is to way to low if you have a P1. I dont think you can mill those heads that much. What size chambers have you and what pistons?
Throw a F1R head unit on the car and 8:3 is perfeckt and much more fun! P1 sucks.

 

If you already have the P1 why not just send it back to ATI for an upgraded impeller to make it a D1--it's less than the $2500 you speak of.

Also, If you did buy a D1 @ $2500 you coud also re-sell your P1 to offset ~$1500 of the costs which would bring it down to ~$1000 (comparable to the ATI re-build).

For the low 8.3 cr, either mill the heads or install different pistons. The head gaskets won't make that much of a difference unless they're extremely thick which I doubt.

 

Thats what I was thinking. Its like $1200 to have the P1 upgraded but, if I sell my P1 then it is only like an extra $1000 to buy the whole new headunit with that all important warranty. I was just figuring that with all the people converting over to the new line of blowers, there might be a few D1's or F1's laying around that could be had for less than $2500. Thanks for the input but, no one has really answered my question about the C/R. Is it too low for a D1? Im sure this will be more detonation resistant but, im thinking it should be more around 9.1:1. Id like to hear everyone's .02 cents. Thanks.

 

You'd be fine with an F1R on your 346, especially with your low compression. It's a little too low IMO.

I recently switched from a D1SC to an F1R on my forged 346. 9.0:1 compression. An 8 rib setup from A&A or ECS is a MUST though. The 6 rib pulleys just can't get the job done without the belt slipping.