Jcurley5

I was wondering what size head gasket I needed to bring the compression ratio on a 97 gt (with PI heads) back to its original 9:1?

I am going to do a PI swap on my 97 gt with 148,000 miles. I have had this car since I was 15 and I plan on keeping it for as long as I can ( I take very good care of her). My dream is to have a sick turbo setup when I am all done with everything, but I don't plan on spending much cash until I finish my Engineering Degree and get a real job. I want to plan for the future and keep a lower compression ratio for a turbo setup, but I am wondering if I am looking to far into the future. If I were to use thicker gaskets to low the CR, I would probably do the work right the first time and get a set of Cometic gaskets that I hear are great on turbo setups. This could be a few hundred dollars more and it might be a waste if I am going to wait a couple years for any forced induction. I am also concerned about the amount of miles on the rotating assembly and block. Should I use the stock size head gaskets that would make it cheaper but would give me a 10:1 compression ratio? My thought behind this was I could wait till the bottom end busts and then build a bullet proof setup for a turbo.

I use this car for allot of highway miles, dose a higher compression dramatically affect my gas millage? What do you Think?

Chris98Gt

Put it together with factory stuff for now get more power with the added c/r atm. then Youll want to rebuild the motor with forged rods and dished low compression pistons at least for a turbo setup later. no since in turboing a stock shortblock if you want power.

MikeInCape

As said above - Running high compression is not good for power adders. Eventually you will just start blowing head gaskets.

IMO - Build your motor when you're ready, and set it up for the turbo.

Drive the hell outta what you have now. If you want to blow it up, it either never will, or will explode very quickly. That's my experience.

Sxynerd

To go a little further: It's not that high compression and power adders are bad its that pump gas can't support it.

Also stock compression is 9.3:1, a PI swap will increase compression to about 10.5:1. Low boost will be fine (6-8lbs) if you keep the power under 400. I would also extremely suggest an I/C of some sort to cool the charge.

A SuperChargers job is to raise the compression by adding pressure.

If you are planing on doing all of this, it would only be smart of you to build the bottom end first. I know it's not instant gratification but it'll ensure that you wont be broke on the side of the road at the worst possible time.

mia96gts

I am getting the swap done next weekend. I will use stock head gaskets for the set of heads I got from a 2000 GT. I preffer using the gain of compression for now since I wont be using a s/c or Turbo for now. I probably will use a bottle which will help much more since nitrous likes high compression more. BUt if I were you I would just put the stock gaskets for now till your ready and besides when you decide to do the turbo setups you can just put the new gaskets in.

Jcurley5

Thank you guys for such quick responses. I am going to take your advise and do the PI swap while keeping the stock gasket size. I had a couple more questions that I have been searching around for but have not gotten a good answer.

1. Will I see a drop in gas millage after the swap? how much?

2. What type of gas should I use after the swap? I wont, but, Could I run ethanol safely with the higher CR?

Chris98Gt

If you get the car tuned you shouldnt lose any mpg, you may even gain some if you drive normally. I'd run 93 and have it tuned for 93. As for the ethonol, are you asking if its ok to run the gas with up to 10%? Most of the pumps I fill up at use this type of fuel and my car still runs ok.

jeff37110

Hey, Chris did you have to do anything to your pistons to clear stage 2 cams with the PI swap?

Chris98Gt

No they were stage 2 npi cams, only 500 lift, 232/230 duration.

jeff37110

ok so stage 2 pi cams are out of the question?