Modded Mustang Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
171 Posts
Discussion Starter #1
Im building a 97 npi block and have trick flow heads with cms 2.5 blower cams going on it. my block will be done soon at the shop and im having it bored 30 over. so im wondering if any of you guys could recomend cc's for the piston, this is going to be a boosted motor on about 12psi. and capabilities to go up in psi if i need to. so im thinking 23cc dished pistons will put me around 8.7 cr? any insight?
 

·
Registered
Joined
·
4,531 Posts
^agreed, which heads do you have teh 38cc or the 44cc. that alone will make your static compression jump a whole point. IMO i would shhot for close to stock compression.
 

·
a.k.a. Racecougar
Joined
·
4,775 Posts
If I've done my math right, a 23cc dish piston with the following:

38cc combustion chamber volume
0.030" overbore
stock stroke
3.62" headgasket bore dia.
0.036" headgasket compressed thickness
Pistons 0.008" below deck

Would work out to a 9.55:1 CR.

22cc pistons would be 9.68:1 CR.
21cc pistons would be 9.81:1 CR.
18cc pistons would be 10.22:1.
16cc pistons would be 10.52:1.

Deck height, headgasket choice, and compression height are going to effect the actual CR. I'd shoot for 9.5:1 - 10:1 for a pump gas street engine, provided you're using some form of charge air cooling at 12 PSI.
 

·
Lexus FTW
Joined
·
4,411 Posts
^agreed, which heads do you have teh 38cc or the 44cc. that alone will make your static compression jump a whole point. IMO i would shhot for close to stock compression.
Agreed. With a supercharger I would stay closest to stock you can. 8.7 is pretty low from my understanding unless your running some serious psi out of a turbo
 

·
Registered
Joined
·
171 Posts
Discussion Starter #8
thanks for the input im going with the 23cc dished, how many psi could push with intercooler? also what if i added meth injection?
 

·
Registered
Joined
·
2,720 Posts
I am running about 8.5.1 compression on my motor with my paxton. Only running about 11psi right now but plan to run about 18-20psi once my trans is built and I upgrade the fuel.
 

·
a.k.a. Racecougar
Joined
·
4,775 Posts
you think i could make 15psi intercooled with 9.5 cr?
You could, but your ignition advance will be limited on 93 octane. At that boost level, methanol injection or a higher octane fuel would be very beneficial.
 

·
Registered
Joined
·
2,720 Posts
You could, but your ignition advance will be limited on 93 octane. At that boost level, methanol injection or a higher octane fuel would be very beneficial.
Like he said you could but to do it safely I would recommend running methanol with 93 octane.
 

·
US Air Force (retired)
Joined
·
13,542 Posts
you think i could make 15psi intercooled with 9.5 cr?
Probably. JKolbfleisch is running 10.5:1 compression ratio with a turbo at 13 psi making 645 rwhp/652 rwtq. He sent me an article from the March 2012 Ford Mustangs | Mustang GT, Cobra, Saleen & More - Muscle Mustangs & Fast Fords Magazine. The test motor was bored .020 over, had Trick Flow .38 cc heads, had a compression ratio of 10.5:1, was running 16-17 psi through a ProCharger P1SC-2 with 18 degrees of timing on 93 octane pump gas.

According to the article Mike Dezontell of Dez Racing said, "The efficient combustion chamber lets us get away with more compression, more ignition timing, and more boost than the ported stock heads."

The test motor made 540 rwhp with stock PI cams. It made 602 rwhp with Trick Flow stage 1 cams. Trick Flow stage 2 cams resulted in 616 rwhp.

I really think that with those heads you will be fine with 9.5 compression ratio. You might even want to bump it up to 10:1.
 
1 - 16 of 16 Posts
Top