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Unread 05-28-2004   #1 (permalink)
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Question GT40 vs GT40P cylinder Heads?

I am rebuilding a 302 and i have most of the lower end complete however I am having a dilema deciding what heads to use. I have a set of stock heads which i really dont want to put on considering i have been beefing up the lower end to handle some extra horses. I really am not on a budget to buy a new set of aluminum heads either. Ive heard that the gt40 heads are a good improvement from the stock heads. However i've also heard that many of the early and late model explorers and mountainers that have the 5.0 come stock with GT40P heads. I would love to just go over the the junk yard and rip the heads off an explorer it would save me alot of time and frankly mustangs are pretty ripped up the second they hit the junk yard making it pretty hard to find what you need (especialy the cobras).

I really would like to know if there is any difference between the two and if anyone has tried bolting on the gt40P's on their mustang how they perform. Thanks alot! :thumbsup
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Unread 05-29-2004   #2 (permalink)
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Quote:
Originally Posted by hfmetal13
I am rebuilding a 302 and i have most of the lower end complete however I am having a dilema deciding what heads to use. I have a set of stock heads which i really dont want to put on considering i have been beefing up the lower end to handle some extra horses. I really am not on a budget to buy a new set of aluminum heads either. Ive heard that the gt40 heads are a good improvement from the stock heads. However i've also heard that many of the early and late model explorers and mountainers that have the 5.0 come stock with GT40P heads. I would love to just go over the the junk yard and rip the heads off an explorer it would save me alot of time and frankly mustangs are pretty ripped up the second they hit the junk yard making it pretty hard to find what you need (especialy the cobras).

I really would like to know if there is any difference between the two and if anyone has tried bolting on the gt40P's on their mustang how they perform. Thanks alot! :thumbsup
The GT40 and GT40P are both good heads. In stock form, the P heads are a little better. The 95-early97 Explorers had GT40 heads and the later97 up Explorers had GT40P heads. You can indentify them easily two ways - the GT40 heads have three virtical bars on the front of the head with a "GT" cast into the head just below the #1 exhaust and the P heads have four vertical bars and "GTP" cast into them in the same place. If you need to keep emissions stuff, the P heads do not come with the thermactor air holes drilled into the back of the head. I am VERY happy SOTP with my P heads and will be dyno tuning soon.
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Unread 05-29-2004   #3 (permalink)
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What the Head Master said !!
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Unread 09-05-2009   #4 (permalink)
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Ok. I know this is a really old thread, but does the GT-40p heads have the EGR hole in them, like the GT-40's?
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Unread 09-05-2009   #5 (permalink)
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Originally Posted by YardSpecial View Post
What the Head Master said !!

at least the "stock head master"....:hihi: sorry moss
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Unread 09-05-2009   #6 (permalink)
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Originally Posted by 50fanatic View Post
Ok. I know this is a really old thread, but does the GT-40p heads have the EGR hole in them, like the GT-40's?
The egr runs from behind throttle body to the header it ain't got nothin to do with heads. You probably meant to ask about the thermactor plumbing in the heads that has the crossover pipe in the back of the engine. It recieves air from the smog pump and injects it into the exhaust ports of the heads for emission reducing purposes. The gt40ps don't have that I don't even know if they could be machined so they would. If they could it would probably be a very expensive procedure that wouldn't be worht it:nogrinner
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Unread 09-05-2009   #7 (permalink)
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Quote:
Originally Posted by ryan7662 View Post
The egr runs from behind throttle body to the header it ain't got nothin to do with heads. You probably meant to ask about the thermactor plumbing in the heads that has the crossover pipe in the back of the engine. It recieves air from the smog pump and injects it into the exhaust ports of the heads for emission reducing purposes. The gt40ps don't have that I don't even know if they could be machined so they would. If they could it would probably be a very expensive procedure that wouldn't be worht it:nogrinner
I don't notice any EGR stuff on my headers. It's a 93'. You know that egr hole that is located in the middle of the lower intake which has a small path through the upper intake into the EGR spacer?
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Unread 09-07-2009   #8 (permalink)
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Quote:
Originally Posted by 50fanatic View Post
Ok. I know this is a really old thread, but does the GT-40p heads have the EGR hole in them, like the GT-40's?
Yes, they do. My P heads have been drilles to accept the thermactor air too. I think you could skip the thermactor air as the air only gets directed there during intitial startup and then the diverter valve sends the air to the cats.
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Unread 09-07-2009   #9 (permalink)
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I thought there wasn't much of a difference between the 91 5.0HO and the sn95 5.0HO other than the throttle body. I have a 95 gt and the egr goes from the passenger side header tube and entered the intake behind the throttle body. Theres a pipe I have to unscrew every time I want to remove my headers. Maybe the pre sn95 5.0Ls egr was totally different and that may be true and if so my bad dude. My 84 lx had no emission equipment when I got it......or even a engine for that matter

Did you have your gt40p heads machined to have the thermactor plumbing tmoss. My set of p's don't have any thermactor plumbing from what I can see. What did the shop do drill a hole stright through head right above the exhaust ports. This may be a easy common procedure I just haven't heard of anyone doin it.
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Unread 09-07-2009   #10 (permalink)
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Quote:
Originally Posted by 50fanatic View Post
I don't notice any EGR stuff on my headers. It's a 93'. You know that egr hole that is located in the middle of the lower intake which has a small path through the upper intake into the EGR spacer?
Yeah it may be different I just didn't think the other HO 5.0s were that completely different but my memory may be failing me. But egr is exhaust gas recirculation where exhaust gas is shot back into your intake charge. It wouldn't make sense if it was located in the lower intake manifold and routed air to the egr spacer. Wouldn't that just be regular intake air being injected into the egr spacer and not exhaust gas? I'm sorry but that just dosen't sound right at all.
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Unread 08-24-2010   #11 (permalink)
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quick Q would the gt 40 heads still work with the bbk long tube headers im already running with my stock H.O. heads ?
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Unread 08-24-2010   #12 (permalink)
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Quote:
Originally Posted by KrOME STANG View Post
quick Q would the gt 40 heads still work with the bbk long tube headers im already running with my stock H.O. heads ?
GT40 heads-any small block ford header will fit..they have the same plug angle/bolt pattern as stock heads

GT40P heads- only certain headers will work,due to the spark plug angle change. the plug sticks out almost 90* instead of on a swept angle
headers known to work with GT40P heads are

mac 1-5/8 longtube
Mac shorty
BBK longtube
BBK shorty
FRPP shorty

most require the use of spark plug wires with 90* ends
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Unread 08-24-2010   #13 (permalink)
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Know (to me) differences:

1: As stated P heads' spark plugs go in at a different angle. This puts the spark at a better place of the combustion chamber, but P heads don't work with any header. Non-P heads do.
2: P heads are known to have a slightly smaller combustion chamber, 58-61cc vs. 60-63cc. This will make for a slightly higher compression ratio.
3: P heads have a slightly smaller exhaust valve, 1.46" vs. 1.54". Both heads have 1.84" intake valves.

Need4spd90 uses P heads and I use F3ZE-AA non-P heads. I believe our cars produce very similar dyno numbers, so take your pick. Both are notably better than stock E7TE-PA heads.
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Unread 11-03-2010   #14 (permalink)
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i was wondering what the hp form stock heads to gt40 and gt40p head wold be
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Unread 11-03-2010   #15 (permalink)
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about 20hp on avg but depends on setup. IMO not enough unless you can get them really cheap and they are bolt on ready. The difference in gt40 and gt40p is not really worth the price of buying special headers. Then when you upgrade you will have to swap again
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