gt40p compresion? and power adders?

The stock compression is 9.0:1. The more cc's a cylinder head has, the LOWER the compression is. The fewer cc's it has, the HIGHER the compression is. I believe the stock heads are 60 or 61cc, and I think the GT40P's are like 62.5cc or something crazy. Therefore, your compression will be lowered to like 8.9:1 or something. Nothing you are going to be able to notice, but it does get lowered slightly.

The question is what do you want your car to be? If you want a street car that will never see track duty, I would get the blower. Who really uses nitrous on the street that much? If you take your car to the track quite a bit, then I would get nitrous. Driveability is going to be determined by the tune of the car, not what is done to the car. You can have a daily driver with a blower, as some of these guys do, however you have to get it dyno tuned and a custom burned chip is a perfect way to finely tune the driveability and safety of the motor.

Joe

No, stock has something like 67cc, the 40Ps are ~58cc

Your compression will end up about 9.5:1

FastmanGT said:

No, stock has something like 67cc, the 40Ps are ~58cc

Your compression will end up about 9.5:1

Click to expand...

Whoever told you that is 100% wrong. I don't think there is a SBF head made with 67cc's. There is a variance between combustion chamber sizes on E7's. I've mostly heard of 58-60cc and GT40P's are like 60.5 or 62.5, I could swear they are bigger. Either way, even if the P's are smaller, that slight change in compression will do nothing. We'll say the compression is 9.0 +/- 0.1.

Joe

Joes95GT said:

Whoever told you that is 100% wrong. I don't think there is a SBF head made with 67cc's. There is a variance between combustion chamber sizes on E7's. I've mostly heard of 58-60cc and GT40P's are like 60.5 or 62.5, I could swear they are bigger. Either way, even if the P's are smaller, that slight change in compression will do nothing. We'll say the compression is 9.0 +/- 0.1.

Joe

Click to expand...

http://www.themustang-net.com/tech_articles/gt40p.shtml

Cliffnotes: GT40Ps have a 59cc chamber
E7TEs have ~63.5cc chamber
My Guesstimates were off, sorry

Half the reason the Ps perform better than the regular GT40s is the increase in compression.

I will post up this weekend how my friends 88 GT with P heads, mass air conversion and Novi 2000 runs.

Fast man where your numbers with all the mods in your sig?

The dyno was with heads, intake, full exhuast, homemade cai, and gears. At the time, the converter was shot and the tranny was slipping. I will get a dyno and air/fuel with all the new bolt-ons and some underdrives once the tranny is back in the car and a few other mods are complete.

I have P heads the reason why they have more hp is the valve sizes and chamber size not compression. I have milled mine .020 for some more compression but it only netted me just a touch more. they are stock compression heads off a explorer v-8.