gt40 vs gt40p

[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.