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Discussion Starter · #1 ·
Another question about GT40P heads! It seems the vote is 50/50. Half say you can run 40p's without special headers the other half says no! Which is it! Anyway, I plan on running the stock headers with the P heads. Will this work with 90 degree wires and/or shortie plugs? Anyone have some pics they can post?
 

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It will not work with stock headers. Some non GT40P specific headers may work, but will require grinding around the flange area. You will also need to modify a couple sparkplug sockets in order to change your plugs. If you do use non 94/95 headers, you will need to block off the EGR system.
 

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The number of people who are duped into buying gt40p heads is unfortunate. Gt40p heads are almost always a bad idea. Between the header issues, required spring upgrades and marginal performance increase they are a waste of money and time. There are plenty of cheap aluminum heads out there that are way way better.


 

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I have a set of shorty headers I purchased off of Prime months ago... the reviews showed they would fit P heads so for the $84 they cost I threw the dice.. They look good, thick flange, and I did a solid test fit the other day and it looks like they are going to fit nicely..
I will try to take a picture tomorrow and paste it......
 

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I have a set of shorty headers I purchased off of Prime months ago... the reviews showed they would fit P heads so for the $84 they cost I threw the dice.. They look good, thick flange, and I did a solid test fit the other day and it looks like they are going to fit nicely..
I will try to take a picture tomorrow and paste it......
Id like to see that. Please test both headers and take pics.
 

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Discussion Starter · #8 ·
I have a set of shorty headers I purchased off of Prime months ago... the reviews showed they would fit P heads so for the $84 they cost I threw the dice.. They look good, thick flange, and I did a solid test fit the other day and it looks like they are going to fit nicely..
I will try to take a picture tomorrow and paste it......
Looking forward to the post!
 

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90 Degree boots will get it done with stock-style headers, but it depends heavily on the brand as not everyone used the same exact routing and such. Still, i've seen it done, and in my mock-up with GT40P heads and BBK 1515 headers it looked like it would work with 90* ends. If you have the heads handy, just bolt up a header on a bench and do some test fitting.

The best headers i found in terms of fit were the old Ford Racing P headers. There was a 94/95 version as well. They are discontinued now, and used sets are trending around $200-300ish.
 

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Curious why you would be interested?? Your post states these are worthless heads and people should buy aluminum heads??
lets just do some quick math...

average cost for unknown mileage used gt40p heads 300$
Cost of upgraded valve springs and retainers 150-175$
New valve guide seals 25$
Cost for Machinist to check them 50-100$
Headers to clear goofy plug angle. 85-300$

Minimum cost to get into a set of gt40p heads is 500$ assuming the buyer has headers that clear the plugs which they rarely do and no machine work needs to be done and they use all stock rockers. Your average person upgrading heads wants roller rockers too. Machine work to make the heads stud mount compatible and then the cost of studs and guide plates and stud rockers or the cost of pedestal mount rockers adds up quick. Either way its another 450-600. Most people are spending 700-800$ after headers to get them to work with stock rockers. For 1050 you can get a set of brand new aluminum AFR heads that will work with any headers or manifolds with no headaches or better yet, regular gt40 heads that have none of the drawbacks the P heads have. Buying used aluminum entry level heads is even cheaper.. Why waste time or money on P heads when you can just do regular gt40 heads and for anyone wanting roller rockers and a good valvetrain, its an absolute waste over arp renegade heads.

And to answer your question, I want to see pictures of what you consider to be clearing the plug wires.
 

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I recently had a set of GT 40 three bar heads redone with larger valves, good HR springs, etc. Total cost for the labor only was $800. Generally its not worth it, however these heads I ported years ago and are going into a 95 Cobra resto.
 

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lets just do some quick math...

average cost for unknown mileage used gt40p heads 300$
Cost of upgraded valve springs and retainers 150-175$
New valve guide seals 25$
Cost for Machinist to check them 50-100$
Headers to clear goofy plug angle. 85-300$

Minimum cost to get into a set of gt40p heads is 500$ assuming the buyer has headers that clear the plugs which they rarely do and no machine work needs to be done and they use all stock rockers. Your average person upgrading heads wants roller rockers too. Machine work to make the heads stud mount compatible and then the cost of studs and guide plates and stud rockers or the cost of pedestal mount rockers adds up quick. Either way its another 450-600. Most people are spending 700-800$ after headers to get them to work with stock rockers. For 1050 you can get a set of brand new aluminum AFR heads that will work with any headers or manifolds with no headaches or better yet, regular gt40 heads that have none of the drawbacks the P heads have. Buying used aluminum entry level heads is even cheaper.. Why waste time or money on P heads when you can just do regular gt40 heads and for anyone wanting roller rockers and a good valvetrain, its an absolute waste over arp renegade heads.

And to answer your question, I want to see pictures of what you consider to be clearing the plug wires.
Are you going to give him an additional $1050?
Ill wait for your answer lol
 

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As someone who started with a set of GT40P's and then ditched them for AL heads, I can tell you that just going with AL heads does add significantly more cost to the project than just the price of the heads. I was discouraged by the expected price to refresh my GT40P's and decided to just take the plunge and bought a set of TFS170's. After that it snowballed because I then needed different rockers, different pushrods, and even had to upgrade the springs on my heads because they didn't really go with the cam I selected after deciding to go with better heads. I went from a simple GT40P/TFS1/Explorer intake combo, to AL heads, custom cam and spring, ported intake, etc etc. Costs snowballed quickly. A9L runs it so-so, (although it manages it better than i thought it would) so i'm in the process of converting to aftermarket ECU.

I do agree with the thought of seeking out regular GT40 heads vs the GT40P's if the OP doesn't have heads yet. At least with the GT40/40P heads you can still run your OEM rockers and pushrods if they are in good shape. That saves you $400-500ish over the cost of going AL depending on your choice of rockers and hardware/pushrods.

Buddy of mine put together a 306 with GT40P heads, B303 and Cobra intake. Had 3.08's, full exhaust and a shifter and that was it. A9L ran it beautifully. It was a simple, common setup and to this day one of the most fun combo's I've ever driven in a street car. Sometimes i wish i kept to my "simple" plan.

BTW, i ended up selling my GT40P's for $40. I originally listed them for $200 and struggled to get anyone to come get them as i dropped the price. Wish i kept them, but doubt I would use them now.
 

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Discussion Starter · #15 ·
As someone who started with a set of GT40P's and then ditched them for AL heads, I can tell you that just going with AL heads does add significantly more cost to the project than just the price of the heads. I was discouraged by the expected price to refresh my GT40P's and decided to just take the plunge and bought a set of TFS170's. After that it snowballed because I then needed different rockers, different pushrods, and even had to upgrade the springs on my heads because they didn't really go with the cam I selected after deciding to go with better heads. I went from a simple GT40P/TFS1/Explorer intake combo, to AL heads, custom cam and spring, ported intake, etc etc. Costs snowballed quickly. A9L runs it so-so, (although it manages it better than i thought it would) so i'm in the process of converting to aftermarket ECU.

I do agree with the thought of seeking out regular GT40 heads vs the GT40P's if the OP doesn't have heads yet. At least with the GT40 heads you can still run your OEM rockers and pushrods if they are in good shape. That saves you $400-500ish depending on your choice of rockers and hardware/pushrods.

Buddy of mine put together a 306 with GT40P heads, B303 and Cobra intake. Had 3.08's, full exhaust and a shifter and that was it. A9L ran it beautifully. It was a simple, common setup and to this day one of the most fun combo's I've ever driven in a street car. Sometimes i wish i kept to my "simple" plan.

BTW, i ended up selling my GT40P's for $40. I originally listed them for $200 and struggled to get anyone to come get them as i dropped the price. Wish i kept them, but doubt I would use them now.
You nailed it! I’m setting up a very similar combo. I wanted to stay with iron heads with smaller valves and more velocity to build torque at the low end. Peak HP isn’t the goal! Low end max torque is way more fun on the street. Will pull really nicely from 1500-4500 RPM! A tire shredder with good street manners! Can’t decide if I should stay with the stock cam. Not much bigger if not. Question….don’t the GT40 and GT40P use the same rockers and pushrods? BTW, paid $50 for the heads!
 

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You nailed it! I’m setting up a very similar combo. I wanted to stay with iron heads with smaller valves and more velocity to build torque at the low end. Peak HP isn’t the goal! Low end max torque is way more fun on the street. Will pull really nicely from 1500-4500 RPM! A tire shredder with good street manners! Can’t decide if I should stay with the stock cam. Not much bigger if not. Question….don’t the GT40 and GT40P use the same rockers and pushrods? BTW, paid $50 for the heads!
Small ports do not make more torque. If that were the case, just buy a set of 221 SBF heads and have at it.....
 

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Question….don’t the GT40 and GT40P use the same rockers and pushrods? BTW, paid $50 for the heads!
Yes. I meant to include the GT40 and GT40P together in that statement. The rockers on the 40P's are identical to the ones on the Mustang. If you wanted to really do this on a budget, you could swap the HO springs over to the 40P's and run the stock HO cam along with the stock pushrods. Slap a $100 explorer intake on it and call it a day. Maybe for an extra bump you add some 1.7 RR's on top of that. I had a set of the F3ZE-6529-AB cobra rockers to go with mine.

Will it put down earth-shattering numbers? Of course not. But it's simple, will idle well and drive nicely.

I mean, if you want to splurge, FTI does sell a GT40-specific cam grind, but by the time you get that and the necessary springs, you're once again going down the rabbithole of scope-creep. I can show you a stack of receipts from my build that will show you how that ends up
 

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Are you going to give him an additional $1050?
Ill wait for your answer lol
That wasnt the only option, guess you stopped reading "or better yet, regular gt40 heads that have none of the drawbacks the P heads have "
 

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Yes. I meant to include the GT40 and GT40P together in that statement. The rockers on the 40P's are identical to the ones on the Mustang. If you wanted to really do this on a budget, you could swap the HO springs over to the 40P's and run the stock HO cam along with the stock pushrods. Slap a $100 explorer intake on it and call it a day. Maybe for an extra bump you add some 1.7 RR's on top of that. I had a set of the F3ZE-6529-AB cobra rockers to go with mine.

Will it put down earth-shattering numbers? Of course not. But it's simple, will idle well and drive nicely.

I mean, if you want to splurge, FTI does sell a GT40-specific cam grind, but by the time you get that and the necessary springs, you're once again going down the rabbithole of scope-creep. I can show you a stack of receipts from my build that will show you how that ends up
You can probably get away with the springs but I dont believe e7 springs in gt40 or P heads will give the correct seat pressure, im not an expert though. The place I get springs lists different springs for those applications. A dropped valve ruined my day once, so I try not to skimp with springs

If OP is going to spend money on rockers, thats when it starts to not make sense to me, that is unless they can be found for 50$ like the heads. Then yeah why not. Ive seen so many P cars with burnt up plug wires or dented up headers that I just dont like them. Without the illusive P specific headers, its not worth it to me.
 
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You can probably get away with the springs but I dont believe e7 springs in gt40 or P heads will give the correct seat pressure, im not an expert though. The place I get springs lists different springs for those applications. A dropped valve ruined my day once, so I try not to skimp with springs

If OP is going to spend money on rockers, thats when it starts to not make sense to me, that is unless they can be found for 50$ like the heads. Then yeah why not. Ive seen so many P cars with burnt up plug wires or dented up headers that I just dont like them. Without the illusive P specific headers, its not worth it to me.

Your prob right. I never looked into it. The spring kits from Alex parts are made for the application and what i would have run had I stuck to that plan. Inwould recommend the OP do the same


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