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I just pulled off my valve covers to discover the heads have a marking that says "GT40P".
Anyone got any info?
That's what the later 5.0 Ex's had.
The GT40P is a modified version of the GT40 Cobra heads that came standard on 97-back 5.0 Explorers. Among other things, the P has reangled spark plug holes and slightly smaller exhaust valves.
GT40P's are very good performance heads and so is the stock 5.0 Ex intake manifold. The main thing that is holding that engine back is the hideous set of stock exhaust manifolds.
Last edited by V8 Level II; 04-04-2007 at 09:15 PM.
According to my research, the GT-40P replaced the standard GT-40 on the V8 Explorers and Mountaineers in early 1997. These are the same heads found on the Cobra's!!!!
is there any difference in the exhaust ports on them? if i were to run these on my 302 would the headers from the swap kit still work?
Ordinary "swap headers" for 5.0L Rangers are for 97-back and do not fit the 98+ engine bay. There are 5 kinds of exhaust manifolds/headers that will work on a 1998+ 5.0 Ranger.
Stock Explorer 5.0L cast iron
Stock Explorer 5.0L stainless
FRPP Explorer 5.0L headers
Torque Monster Headers
Custom
GT40 and GT40P have about the same port outlet shape. It would be a good idea to consider spark plug wire vs. header interference since the heads have different plug angles.
* The GT-40P replaced the standard GT-40 on the V8 Explorers and Mountaineers in early 1997. Yes, that's right, the Explorers got Cobra heads (although the Cobra's heads were milled to bring it's larger combustion chamber down to the size of the E7TE to keep compression up).
* Similar runner volumes to the standard GT-40 head (around 145-155cc on the intake side, I think, compared to E7TE's 124cc). Also flows similar intake and exhaust cfm numbers to the standard GT-40 head. All accessory bolt locations and valve train geometry are the same as the standard GT-40.
* 1.85/1.46 valves (compared to 1.85/1.54 for the standard GT-40). The exhaust port was redesigned and is more efficient, thus the ability to use the smaller exhaust valve. This actually works well since to get equal flow numbers the velocity must be higher.....exactly what we want.
There's a little bit of room for larger valves but start going larger on the intake side and you're going to have to grind on that plug boss to clear it. And....don't forget.....a bigger valve isn't necessarily better. The whole reason these heads work so well is the decent flow they provide while still having smaller port dimensions. If you're not careful and hog out the bowls for big valves you could easily hurt flow. Just remember this when planning your mods.
* Smaller 59cc (up to 61cc based on factory tolerances) combustion chambers (65.5cc in unmilled GT-40 w/ FRPP valves). Great for NA cars as this equates to a raised compression ratio when switching from E7TE castings. Should get you close to 9.5:1 (w/ stock pistons). Cut 0.030" off the bottom and you're close to 10:1 (w/ stock pistons).
* Small emissions-type bump in exhaust port similar to E7TE casting but it's nowhere near as pronounced. This bump is dead center on the port roof right at the exit. Easily removed if you feel it's hurting flow. I removed mine, smoothing the transition from the guide boss to the port exit. I raised the roof of the port here to eliminate the offending bump and open the port to a size a bit closer to the Fel-Pro 1415 gasket.
* No thermactor holes in the front/rear face to plug and no hole in the exhaust port to mess up flow.
* Intake ports are already very close to a Felpro 1250 gasket...probably no need to gasket match. Mine were only off on one end.....the other three side being almost perfect. I just matched the last side.....no sweat.
* They can use stock pedestal mount rockers. I upgraded to stud-mount adjustables. Be sure to get a shim kit to ensure you'll get the rockers to torque down correctly if you're using bolt-downs. You may not need 'em if you don't mill the heads but the kit is only $10.
* Spark plug is moved down and rotated out placing the electrode closer to the center of the combustion chamber. This provides a better and more complete burn. Not only does this help performance but it also reduced emissions. Note: The GT-40P's don't use standard 5.0L plugs. You must use plugs for a 98+ Explorer/Mountaineer V8 or for a Cobra/Lightning equipped with iron GT-40 heads!! Forget about the shorty plugs (Accel p/n P526S). I've heard they're close to $10 each for this application! Plug specs are: 14mm thread, 0.708" projection, tapered seat, resistor plug. Thanks to Derek Hyde for the Accel plug specs!!. The 2000 FRPP catalog lists a Motorcraft AWSF-32C. I bought Champion Truck Plugs p/n 4013 (I used the Truck Plugs on a '97 V8 Dakota I had and was happy with them. Thought I'd try 'em again.)
* Standard unequal length shorty headers won't work because of this new plug location. The primary pipes make their downward turn towards the collector too soon. Central Coast Mustang offers a P-specific shorty (made by MAC) for $199 and FRPP is offering a set for about $250. I know the FRPP pieces are stainless.....not sure about the MAC....most likely their HTS coating. I thought I read once that stock tubular exhaust manifolds might work. Why bother using those though if you're upgrading the heads?
In starting my research for the header-fit table I've been told that standard FRPP unequal length shorties will work for not only the Fox application but the SN95 shorties will work for the 94-95 cars as well. These are not a perfect fit like the MAC-for-CCM shorties and will most likely require 90° boots and/or heat booties, but they are supposed to fit without any primary dimpling.
* Equal length shorties won't work at all. Well....sort of. Again....in researching the header-fit table it looks, via some good installed shots - don't have provider's info handy....credit will be given) that BBK equal length headers may fit. Still studying the pics for a more solid opinion on this.
* Some longtubes and 3/4 length headers will work. Their ability to allow the primaries a longer exit straight from the exhaust port b4 turning down towards the collector provides adequate access to the plug. I know of MAC longtubes (1 5/8"), Flowtech longtubes (1 5/8"), and Heddman longtubes (1 1/2") being used.
The Heddmans alledgedly require a small clearance dimple on the #4 primary. The MAC's are snug on the #7 primary but clear fine. CCM offers these as a longtube alternative to their P-specific shorties. I had unknown-brand 3/4 length headers (1 1/2") on my '84 (look like DynoMax) that will clear no sweat. MAC longtubes for the SN95's are a good fit. CCM finallyhas a SN95 P-fit shorty. CCM is also offering a set of Tri-Y headers for GT-40P use in classic Mustangs. This is a huge plus as I've had many questions regarding header fit for P's in classic 'Stangs.
The Flowtechs were originally thought to work and they can be used. The dimple that was said to be required in the #4 primary is more like a crater. You need to crush the primary half closed to clear everything. And you'll need wires with 90° to clear a few of the other primaries as well. Check out the Progress Page for more info on this. There's some great shots of the Flowtechs installed (and "dimpled") as well as the CCM MAC built P-specific shorties.
* P heads take a 7/16" headbolt just like other 289/302 heads. No funky stepped bolts or bushings needed. Big plus IMO here. Bad for 351W installs but great for us 302 based users.
Does anyone (Bob?) know if a set of long tube headers works with the coils-sprung (2wd) Ranger engine bay? I HAVE to get rid of those nasty lookin cast headers.
Does anyone (Bob?) know if a set of long tube headers works with the coils-sprung (2wd) Ranger engine bay? I HAVE to get rid of those nasty lookin cast headers.
Regular long tube headers from other apps won't fit. The closest thing is the Torque Monsters ($689!) that are custom made to squeeze into the cramped 5.0 Explorer bay (virtually the same as the 98+ torsion bar Ranger bay). You should contact BrianB31 to see if he has any more insight about headers in the coil spring truck.
Regular long tube headers from other apps won't fit. The closest thing is the Torque Monsters ($689!) that are custom made to squeeze into the cramped 5.0 Explorer bay (virtually the same as the 98+ torsion bar Ranger bay). You should contact BrianB31 to see if he has any more insight about headers in the coil spring truck.
Holy crap those torque monsters are so pretty!!! However, when you flip over that price tag and take a look, it makes me want to puke!! Plus...if those are considered "long tube", that's a pretty short tube!
I'll probably go with a set of FRPP or I'll get mine ceramic coated. Can you ceramic coat a set of cast headers?
as far as the GT40ps, well p= piece...they are pretty garbage, i tried em on my truck and it rlly had no more than stock, i put a set of ported and fully rebuilt GT40's from the 93 cobra and made a very noticable difference..
also bout the headers, my truck is one of the early years, 84, but i put on a set of james duff longtubes, and only had to replace motor mount bushing and they just slipped in...drivers side throught the bottom went very easy..as far as the passenger side, like i said through the bottom, different motor mount bushing, and a very slight notch in frame rail, and went in, and even w/ motor shaking, doesnt hit rails...
also bout the headers, my truck is one of the early years, 84, but i put on a set of james duff longtubes, and only had to replace motor mount bushing and they just slipped in...drivers side throught the bottom went very easy..as far as the passenger side, like i said through the bottom, different motor mount bushing, and a very slight notch in frame rail, and went in, and even w/ motor shaking, doesnt hit rails...
Unfortunately, the situation is very different for 98+ Rangers which have a different frame, suspension, and engine bay layout. There are no commercial long tube headers that will fit. The Torque Monster headers are the best available for 98+.
Has any used the Ford Performance Natural Shorty Headers for GT-40P Heads (79-93 5.0L) on a second (1993) 2wd Ranger swap? I really haven't found anything. Have a 331 with GT40P heads and a new set of these headers for a different swap I had planned. Thank you
Ford Performance Natural Shorty Headers for GT-40P Heads (79-93 5.0L)
04-04-2007
