Fox What to do with heads

Jimmer009

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Jan 4, 2022
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So my current set up is heads xcam and cobra intake. I also have megasquirt and a msd 6al. Long tube headers and a x pipe.

My heads are speed master 190cc, 2.02 intake 1.65 exsaust valves, with a 64cc combustion chamber.

So my question is; if I plan to stay n/a should I go with set of gt40 heads??? I feel like I'm giving up a lot of power as I'm losing compression with the aluminum heads.

Thanks for all the help.
 
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Jimmer009

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Jan 4, 2022
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I currently have them on my car. I thought h/c/I would give me more power.

I'm not sure I guess I'd ave to measure piston to valve clearance. But are you saying mill/deck the heads or the block?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Tell us more, trans, throttle body, rear gears, timing.
The name of your first pet :rolleyes:
what year mustang do you have
The Gt40 heads are around that same combustion chamber size but the valves are smaller, the P heads are about 61 cc (IIRC) so there is a slight compression bump, but there's more to it than getting the compression higher.
 

Jimmer009

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Jan 4, 2022
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So 5 speed trans, 75mm throttle body, 4.10 gears, I think my tune calls for 34 degrees max timing. It's white and red

I'm thinking I just got a turbo build going on. I just can't afford the turbo kit yet
 

bird_dog0347

still married haven't seen testicles in years
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I'd like to do no prep racing. Other than that it's a street warrior.

My goal is to get close to 500hp.
If you want close to 500 HP you'll need boost or nitrous, if you do boost you'll want the lower compression... if you do N2O you'll want the higher compression. If you can't afford the turbo kit yet, then making big changes to the engine won't help you afford the turbo and will only slow you down.
 
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AeroCoupe

Founding Member
Oct 28, 2001
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So 500 fwhp or rwhp because you are not going to get either one with a NA 302 without dropping some major coin on it. There are plenty of motors out there making good hp with 9:1 to 11:1 compression ratios. I will say that the cam is the brains of the motor and you typically select the cam based on what you are trying to do with a specific cubic inch motor. From there you select heads and intake and build the motor around that.

So can we assume this is on a stock short block minus the X cam? Assume the headers are 1-1/2" primary into a 2-1/2" fire cone? Is the exhaust system 2-1/2"? What is your shift point in rpm? Can we assume you have a bigger than stock fuel pump? More questions are what size injectors, what MAF, and do you have a CAI? Another question that will directly affect compression ratio is what head gasket did you use? They have different thicknesses so it will affect it and may not be a huge amount but when looking for a little more power NA it counts.

What I am trying to drive home here is you are asking if the heads are the issue when we do not know :poo: about your car, setup, tune, etc. The more info you provide the more feedback we can give.

With a stock bottom end those heads are going to get you about a 9:1 compression ratio which is stock. If you can mill them (I do not know the deck thickness but maybe you can call them and see if they can be milled and if so how much) that will provide the most gain. Realize that when you mill them you may end up needing to mill your lower intake to get things to line up. I had to do this with my Cobra lower to match the heads on that motor.

There are plenty of motors out there making good hp with 9:1 to 11:1 compression ratios. I will say that the cam is the brains of the motor and you typically select the cam based on what you are trying to do with a specific cubic inch motor. From there you select heads and intake and build the motor around that.

A quick piece of advice is to get ahold of TMoss over on the Corral ([email protected]) and have him port that Cobra intake as that is a lot of your restriction. Tom ported my old Cobra intake about 15 years ago and it made a huge difference. His son Matt is now doing the porting and from what I have heard he has taken it to the next level. I believe they can port heads as well so you may want to talk to him about that if you want to keep those heads. I will say that he needs to know just about everything we have asked you to provide information wise on the car so he knows how far to take the porting on the intake. The intake needs to match the heads flow wise so things work together and to not create choke points or lazy flow.
 

limp

wrap a little cheese around it and its a done
Oct 4, 2020
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I'm running the Gt40P heads. If you look into it they are actually better than the 40's. Just make sure you upgrade the springs. That's the weak point of them.
DSCF0824.JPG
 

AeroCoupe

Founding Member
Oct 28, 2001
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The GT40P’s have a smaller header selection and have the spark plug angle/boots issue. Both minor BS stuff IMO and a great head for the $$$ especially if you can score a set off an Explorer.
 

Hot Stang

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Aug 19, 2022
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The GT40P’s have a smaller header selection and have the spark plug angle/boots issue. Both minor BS stuff IMO and a great head for the $$$ especially if you can score a set off an Explorer.
I had no problem with mine. I'm running shorty headers.
 

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Jimmer009

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Jan 4, 2022
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So thanks everyone for helping and working with me. I will do my best to answer all your questions. I'm at work (local highway dept) so I have time but only here and there.

The rest of the mods are 42# injections, stock fuel pump and lines, no maf(speed density) bbk king tube headers 1 1/2 to 2 1/2 collector, the 3" out to the back. .040 head gasket. Cai cheap cone.

My restriction is my intake. I can feel the car run out of steam around 5-5500rpms. I have been in touch with tmoss. I might let him port it this winter. But I'm also looking at the Holley EFI 4150 intake manifold.

I will address the intake this winter. I was looking at stroker kit (different story) but it says 58cc combustion chamber I would 10.5:1 compression. And a 64cc I would have 9:1. This is what got me going on the heads.

Sorry if I forgot something, I'll keep updating if there is more infor needed.
 

Jimmer009

Member
Jan 4, 2022
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I have searched YouTube and the internet. I have not gotten a satisfactory answer on what the Holley EFI single plane intake would be like on a foxbody.

I love the idea of being able to remove my valve covers with out taking off my intake.

As far as performance I see it (I'm guessing) losing some power down low and putting up higher in the rpms. I think because the shorter runners and overall less internal volume of the intake.

if I send my cobra intake to tmoss I might be a couple steps ahead. I won't have to sacrifice any power down low and motor will breath up high.

Here's a link to the Holley intake. 500$ it comes with the fuel rails also
 
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