gt40 vs gt40p

[BLOCKER]

sorry, I know this question has probably been asked about a million times which one is the better head?

Stock, Iron GT40 or
Stock, Iron GT40p ?

Before answering the poll, consider:

You have a choice between a set of heads of a '96 explorer (GT40) or a set of heads off a '98 explorer (GT40p). The headers will not be a problem , because you want to upgrade your existing stock headers and you have not already bought a set that fits the orginal ET7E's. and you aregoing to have them rebuilt anyways so miles is not a concern. Both sets are iron so aluminum is not a factor.

[QuantumMotorsports]

You should definately go for the GT40 P heads. They actually flow better than the GT40 iron heads. I know, it sounds weird, but there have been many flowbench tests done on these heads. The revised spark plug location makes the fuel burn much better and also creates a bit of a swirl in the chamber for fuel mixing. And besides, you can buy a set of GT40P's from me for $200 plus shipping. The GT40 iron heads are much more expensive. If you're interested in a set of the P heads, email me at mblack@ou.edu

[BLOCKER]

How well would they work on a 351?

what size rockers are those?

Yes I am interested, but I was considering "beefing" up an BRONCO, and was wondering how well the heads would work...

Thanks

[TMASTER]

I think the GT40 Iron heads are better for me. There flow data is almost exactly the same as the GT40P's
look:
http://www.jason.fletcher.net/tech/f...a/castiron.htm
My set i have burns the fuel perfect!... gold strap with slighty blue half way.... the dyno A/F was right on 12:1

1. GT40 heads can use normal headers, the P's have to have special headers...$$$
2. GT40 heads work with the factory smog lines, and the P's do not accept factory emissions.
3. GT40 heads have larger Exhaust valves from factory.

just my opinion And i got a pair for $425, that had $600 worth of work done to them brand spanking right outta the machine shop.

[Coupe50h]

im sure the p's are nice, but i got my (non p's) off a 97 exploder, the heads went into a machine shop for refreshing, and .010 mill, i then bought them for 450$ i put them right back in the shop for some porting and 3 angle, then i put new springs on, if i would have had to pay for that port work, i could have already bought some gt-40x and been happier...but oh well
with the better springs i got 4-5 mph with the e-cam, explorer intake, and gt-40 heads, i think ported e7's can match these heads though.

I will say, if your going to just leave them stock, dont bother, but with porting they'll be good, i would rathe rhave ported e7's with some good springs, then some unported gt-40 irons...my .02

[goodyear1984]

gt40 heads are like a e7 with a band-aid.yea they flow a little better,have bigger valves.they dont flow enough on a 302 so dont bother with putting them on a 351.there are so many advantages of aluminum heads..if you sit and think about it u will spend 1300 for a set of good aluminum heads that are brand new...say u get a set of gt40 heads for 200.then to rebuild then springs 150,valve job 150,mill 100,seals 40,hot tank 50.there is around 700 bucks might be less or more depending on what needs to be done to them and the prices at your machine shop.now you have 700 into a set of production iron heads that flow a little better that stock and are good for a 302 nothing bigger.lets say in 2 years you decide you want to build a 331 or a 347 stroker if you have aluminum heads you can run more compresion on pump gas,they weigh half what a iron head does, they flow way better ,make more power.if you donthave the money now i would stick with the e7 and port them.i got 5 tenths inthe 1/4 mile when i ported a set.then when you have the money buy the aluminum.ive seen people make this mistake befor and are not happy that they barley notice a differance when they bolt on a set on gt40's.its a better bang for your buck to buy the right heads now and not have to buy a different set inthe future

[Unit 5302]

This appears to be an ancient topic, but since the recent comment was made, I feel a need to chime in on this debate once again.

Out of the box the GT-40P's flow better, burn fuel more efficiently, and have a smaller combustion chamber (higher compression), than the GT-40 Irons. The GT-40 Irons you'll usually find have a better valvetrain capable of taking cams with lifts somewhat higher than .500 whereas the GT-40P head stock valvetrain should not be used with cams having a lift over .500 unless you like valvespring bind (which you don't). There should be no debate still out there on which head is superior. The GT-40P is by far the better head, no ifs, ands or buts.

As to the aluminum aftermarket heads vs. a set of GT-40P heads, there is some debate. Bigger is not always better, and the GT-40P heads can make excellent power while not killing your performance below 4000rpm on a small block 302, unlike any aluminum head that's going to be really suited for a 331 or 347 stroker.

Building an engine is not like building a computer where the parts work independently.

If you put a set of big, high performance aftermarket aluminum heads onto a 302 without changing the intake and the cam, you're just going to get an unresponsive, torqueless gas guzzler because the port velocity is going to be terrible as the intake won't be able to flow to match. If you put a big intake on the engine keeping with the idea you're going to build the car bigger later, you're still going to have poor intake/head flow velocity because the cam isn't going to allow sufficient overlap, duration or lift to efficiently fill the cylinder. Okay, so what if you cam the little 302 to the moon. Gratz! You now have an engine that should have good port velocity... at 6500rpm, which you can't rev to with the stock rev limiter, and your flywheel, stock bottom end, fuel pump, transmission, fuel injectors, cooling system, and exhaust are incapable of safely supporting. If you manage to upgrade all of those components, you'll have one heck of a powerhouse 302, but for $10,000. Oh, and your fuel economy will suck, and you'll have to keep the engine above 4,000rpm to notice the extra performance. Your low end torque will be significantly worse so you had better be running at least 4.10 gears making 1st gear, and rush hour traffic a nightmare.

In summary, there is absolutely nothing wrong with GT-40P heads for the 302 owner that wants drivability, 320hp or under without forced induction, and the ability to stomp the mismatched 5.0 in the next lane.

[goodyear1984]

lets get one thing straight the stock bottomend will hold 6500 all day long the flywheel (manual) would only break at 6500 it it had stress cracks.cooling system mines stockother than a electric fan,transmission(t5) no problems mine lasted half the summer with over 500hp goin tru it,Dont under estimate a 302 they take a beating.its simple dont waste much money on gt40 heads.go with 165 afr a rpm preformer intake and a decent cam.then a 100 on a fuel pump and 200 a set of 24lb injectors.u aint gonn flow enough air tru a set of untouched gt40 heads to make 320 hp.with the gt40 and a intake ud be luckey toget 265hp.if thats what ur looking for thengoit if u wanna make over 300 then save ur money and get some aluminum heads intake cam.u will pick up power just on the cr gain

[Unit 5302]

Originally Posted by goodyear1984

lets get one thing straight the stock bottomend will hold 6500 all day long the flywheel (manual) would only break at 6500 it it had stress cracks.cooling system mines stockother than a electric fan,transmission(t5) no problems mine lasted half the summer with over 500hp goin tru it,Dont under estimate a 302 they take a beating.its simple dont waste much money on gt40 heads.go with 165 afr a rpm preformer intake and a decent cam.then a 100 on a fuel pump and 200 a set of 24lb injectors.u aint gonn flow enough air tru a set of untouched gt40 heads to make 320 hp.with the gt40 and a intake ud be luckey toget 265hp.if thats what ur looking for thengoit if u wanna make over 300 then save ur money and get some aluminum heads intake cam.u will pick up power just on the cr gain

You're rolling the dice a little with your engine, and you may be getting great results, but I wouldn't feel safe taking a stock bottom end that high without at least upgrading the bearings. You might get away with it, but not everybody will. The 5.0 is stronger than it's given credit for, but that doesn't mean everybody has a 5.0 that's balanced as well as yours or in tip top shape at 80k miles.

Unmodified (not ported, no oversized valves) GT-40P heads were enough to push Jeff Chambers to 120mph, and they will not be a bottleneck up to about 325hp. After 325hp, they'll either need to be ported or aftermarket aluminum heads will be needed. That said, 325hp on a fox body Mustang is more than enough to get your traps into the 110mph+ range. If you hook up, you should be in the low 12s with a streetable combination, N/A, without revving beyond 6000rpm, and with a very strong torque curve.

The AFR 165s won't really restrict power production until the 400hp range (or higher with a high lift cam). That said, a N/A 302 will rarely see that kind of power production. Most street combinations will sit in the 360hp or lower area, even with pretty aggressive combinations (about 300rwhp). The AFR heads are great heads. They've been designed for high port velocity without sacrificing high end flow. That said, their peak hp advantages are limited on a mildly-moderately modified engine, and they will still not match the torque curve and mid range performance of the GT-40Ps. They would also be $800 more expensive than prepped and reconditioned GT-40Ps with bigger valves and an upgraded valvetrain.

[goodyear1984]

ur getting to scientific.6500 is fine for a 302.i mean up grading the cooling system come on dude i have a 347 with over 11.3 to 1 and mine is stock with electric fans doesnt go over 170.if ur engine isnt balanced good enough to 6500 u had a problem at day 1 when it was built u dont need to up grade bearing there only gonna go if theres a balance problem at this power level.if any thing get a good fluidine balancer or a pp balancer.there are so many people that do it to the stock bottom ends its not even funny.i ran 11.8 with a stock bottom end shifting at 6200 for 4 summers and 30,000 miles and now its in a carbed 85 still gettin the crap beat out of it. my friend has a 92 roller bottom end witha 150 shot shifts at 6500.its been done ive done it ive seen it..but that here nor there were talking about heads.bottom line if u can get a set of gt40 heads for a few hunderd and they dont need any work then get them any more than that get aluminum.its just stupid to put money in iron heads.they dissapate heat better via u can run more compression without detanation

[Unit 5302]

Originally Posted by goodyear1984

ur getting to scientific.6500 is fine for a 302.i mean up grading the cooling system come on dude i have a 347 with over 11.3 to 1 and mine is stock with electric fans doesnt go over 170.if ur engine isnt balanced good enough to 6500 u had a problem at day 1 when it was built u dont need to up grade bearing there only gonna go if theres a balance problem at this power level.if any thing get a good fluidine balancer or a pp balancer.there are so many people that do it to the stock bottom ends its not even funny.i ran 11.8 with a stock bottom end shifting at 6200 for 4 summers and 30,000 miles and now its in a carbed 85 still gettin the crap beat out of it. my friend has a 92 roller bottom end witha 150 shot shifts at 6500.its been done ive done it ive seen it..but that here nor there were talking about heads.bottom line if u can get a set of gt40 heads for a few hunderd and they dont need any work then get them any more than that get aluminum.its just stupid to put money in iron heads.they dissapate heat better via u can run more compression without detanation

Haha, my advice wasn't really for you. A 347 is going to run into issues with the GT-40 Iron or GT-40P heads pretty quickly once you start adding a couple other parts so for you, the GT-40Ps don't make any sense.

You can still find the GT-40P heads reconditioned with upgraded springs/valves on Ebay for $500 or so a set.

That said, there is no doubt aluminium heads conduct and dissipate heat better than iron heads so you're right about being able to go higher compression on aluminum heads without detonation. With good gaskets, there shouldn't be any issues with expansion rate differences between the cast iron (cast steel) block and the aluminum heads, either. I can definitely agree 100% with you there.

[Lashbrook27]

This looks like a great conversation. When I bought my 90GT it seemed to be real slow. Even with the 3.73's installed it took of the line like a brick. All at the same time I installed a Cobra Intake, GT40P's, ford racing headers instead of the BBK that were on already, BBK high flow h-pipe, 40 series flowmasters dumped. This car will not hook at all on the street. Once the 3.73's get the rmps to about 3500(quickly) forget about the tires sticking, thats if I take it easy. This is also with the stock 60mm TB. I am looking to pick up a E303 cam that will keep me just under .500 which is perfectly sooted for these heads, to include a set of 1.6 rockers. Matched up with a good fuel system and I will have a nice street car running good 1/4 mile times.

Unit 5302 any ideas on how I should set up the fuel system? Has stock pump, 24lb injectors (i did not install). It did not have adj. regulator, which I did not remove (long story) but it isn't on there now.

1990 Mustang GT 25th Ann: original stock forged short block; gt40p heads; cobra intake; stock tb; 75mm c&l; bbk cold air fender mount; 24lb injectors; underdrive pulley on crank and water pump; msd cap and rotor; msd wires; stock coil; aode with shift kit and cooler; ford racing headers, bbk hi flow h pipe; 40 series flowmasters dumped; 3.73's, bbk lowing springs; 245/45 R17's all around (definitly need a better tire in the rear).

mods soon to come: electric fan for better cooling and to remove robbing crank driven, E303, 1.6 rockers, better tires in the rear

[Unit 5302]

Originally Posted by Lashbrook27

This looks like a great conversation. When I bought my 90GT it seemed to be real slow. Even with the 3.73's installed it took of the line like a brick. All at the same time I installed a Cobra Intake, GT40P's, ford racing headers instead of the BBK that were on already, BBK high flow h-pipe, 40 series flowmasters dumped. This car will not hook at all on the street. Once the 3.73's get the rmps to about 3500(quickly) forget about the tires sticking, thats if I take it easy. This is also with the stock 60mm TB. I am looking to pick up a E303 cam that will keep me just under .500 which is perfectly sooted for these heads, to include a set of 1.6 rockers. Matched up with a good fuel system and I will have a nice street car running good 1/4 mile times.

Unit 5302 any ideas on how I should set up the fuel system? Has stock pump, 24lb injectors (i did not install). It did not have adj. regulator, which I did not remove (long story) but it isn't on there now.

1990 Mustang GT 25th Ann: original stock forged short block; gt40p heads; cobra intake; stock tb; 75mm c&l; bbk cold air fender mount; 24lb injectors; underdrive pulley on crank and water pump; msd cap and rotor; msd wires; stock coil; aode with shift kit and cooler; ford racing headers, bbk hi flow h pipe; 40 series flowmasters dumped; 3.73's, bbk lowing springs; 245/45 R17's all around (definitly need a better tire in the rear).

mods soon to come: electric fan for better cooling and to remove robbing crank driven, E303, 1.6 rockers, better tires in the rear

I just happened to be passing through the Windsor Power forum today...

Well, the 24lb/hr injectors are sufficient (no adjustable regulator necessary), but the stock pump has to go. If I remember correctly, it's 88lph. You need to step it up to at least a 110lph pump, but I'd probably go to a 155lph pump as they're practically the same price and a 110lph pump is pushing it.

Which version of the GT-40Ps do you have? Aftermarket or from an Explorer? The reason I ask is that the heads from the Explorer will be setup with valves that can handle an absolute maximum of .500 lift before they may bind. Taking them to the extreme could result in the problems, and it's certainly more likely to get you valve float at higher rpms.

[Unit 5302]

Originally Posted by joylee

GT40 Iron heads are much better compared to the gt40p, it may have the same functions, but the gt40 is more reliable...

More reliable? More reliable when it comes to? The GT-40P heads result in not only better power production from higher intake and exhaust flow rates, but also better efficiency. If you're talking about a valve train failure, that can hardly be blamed on the head. Using proper components (like valve springs that can handle your camshaft's lift profile) is essential to any engine.

The GT-40 v GT-40P hasn't really been a very debatable topic for the past decade now.

[GodStang]

Ok here is a question. Saturday we are picking up a set of 1996 GT-40 and a set of 2000 GT-40P heads ($50 each). They will get P&P and a 3 angle valve job ($300 total when done). They are going on a daily driver 351w roller in a 68 mustang with a stage I TFS cam and Holley 600cfm carb and edelbrock lower. It will have hedmen hedders long tube for the conversion. Which one will I be better off putting on. Not worried about power just want something nice. With out spending $1000 more for aluminum heads.

[GodStang]

Ok just got back from the junk yard and for $29.99each I got a set of GT-40 and a set of GT-40p heads. I will see what fits the best and go with them.

[Unit 5302]

Wow... $30/ea set or $30/ea head? Either way, those things used to be $500/set, minimum.

Port and polish
GT-40p Advantage = compression ratio. 59cc combustion chamber vs 65.5cc on the GT-40 Iron.*

GT-40p Advantage = low lift camshaft. If we were talking about an XE series camshaft with high lift, it would favor the GT-40 Irons as the Irons do flow a little more at .600 lift.

GT-40p Disadvantage = Exhaust valve size. 1.46 vs 1.54. There is only so much air you can squeeze through the smaller valve on the GT-40p heads.

GT-40p Disadvantage #2 = Headers. The p heads require special headers so I have to wonder whether or not your exhaust options will be as good once the porting/polishing is all done?

*Your compression ratio may get pretty high on the p's. On a stock 69 Mustang with the 351w, you'd be at about 11.0:1 on the GT-40p's and close to 10.1:1 on the GT-40 Irons. I don't know what pistons you're using so that makes it impossible to truly say.

[mjacoby321]

hmmm interesting. The GT-40p has greater features than the GT-40... but the 40p has some disadvantages too... makes me think of purchasing the GT-40p or not...

[triple-aught]

I have a '66 289 2v car and planning to do a stock rebuild on the unmolested eng. the only upgrades now are a holly 2v 350cfm man choke, true duel 2 1/4'' into flowmasters, a msd master blaster coil+ wires, and a k&n air cleaner. Kinda like a stage 1 harley upgrade for a ford. I want to keep it reliable and long lasting more than power but would like to take advantage of the better breathing. I was looking at gt-40 heads as a mild upgrade over the stock thermactor heads (i removed the smog pump and planned to plug the heads when rebulit, temp caped at the valve). but read on this thread that headers are needed? I'm looking at $800 to rebuild the stock heads including hardend valve seats i want to keep the stock man cause of the new welded exh. what does any one recommend for heads and cam? I up graded my 2000 harley twin cam with S&S e carb, opened up the exh. and S&S .510 gear to gear cams (ditch them timing chanes) the next bump up from stock (.479 i think?) and love it! it's reliable, fast and have greatly expanded the powerband. I want that for my car + can anyone tell me what is the stock lift/dur on the stock cam? the car is automatic

[88workcar]

Now you can buy a real nice set of aluminum heads brand new for $800.00. They will be better all the way around, lighter flow better, not too big as to kill the power