gt40 heads vs stock heads

scale · 04-02-2003, 08:46 PM

whats the different with gt40 heads? i have seen alot of ppl run them and just curious to see what the difference is from the stock heads say on a 91 lx coupe.

Coupe50h · 04-02-2003, 09:48 PM

If your reffering to the gt-40 iron, like the heads that came factory on the 93-95 cobra, and early ford exploders, they arent a whole lot better, the valves are bigger 1.84 intake, 1.60 exhaust, i could be a little off on the exhaust size, the stock e7's have a 1.78 intake 1.46 exhaust, again i could be off on that, but it's close, i run the gt-40 heads, i had a mahcine shop port/polish, surface, and 3 angle valve job them, they say mine came off a 95 cobra, but the guy that sold them to me said they came off an explorer, but anyway, i can't tell you the performance they have since my car is still apart, i can let you know maybe monday, i should be threw.
I also hear the 40's respond well to porting, and to notice a big difference from e7's you need to do at least a mild port job.

84LX89GT · 04-02-2003, 09:50 PM

For starters GT40 heads have larger valves 1.84 intake and 1.54" exhaust valves. Also the port casting is much cleaner and smoother, plus the HUGE thermactor air injection bump is gone in the GT40 heads. Also they're faster burn heads because of a revised combustion chamber. I've heard that the aftermarket GT40 heads (cast iron) are supposed to add 30 horsepower to even a stock mustang GT. You can get used GT40 or GT40P heads for VERY cheap (the P heads were used on '96-'99? 5.0L explorers). GT40 heads were originally used on Cobra Mustangs and the 5.8L lightning and also sold through Ford Motorsport.

scale · 04-03-2003, 12:00 AM

do they just bolt right up? Any modifcation?

Maybe i should do this since i am tearing my car down to the heads to put on my cobra intake anyway.

NotchJohnson · 04-03-2003, 12:35 AM

Nope, they bolt right up no problem. Mine are ported to a 1250 intake gasket, and I dont remember what size exhaust. I forgot to get pics of them lined up against stock heads, but there is a big improvement in the exhaust ports. They till dont compare with most of the other aftermarket heads, but they are a decent improvement for cheap if you find a used pair.

red82gt · 04-03-2003, 02:11 AM

My car ran a high of 104mph last year wit a ported set of GT-40's and a worn out Carter carb. They will be a big improvement over stock.

BLOCKER · 04-03-2003, 06:58 PM

If you are going to buy a set of GT40s it is best to go private sale, all of the junk yards I have found know about the desire for GT40's for mustangers and are starting to charge an arm and a leg...

04-02-2003, 08:46 PM	#1
scale Registered Member Join Date: Mar 2000 Location: minneapolis, mn Posts: 158	gt40 heads vs stock heads whats the different with gt40 heads? i have seen alot of ppl run them and just curious to see what the difference is from the stock heads say on a 91 lx coupe. __________________ 1991 LX coupe,AOD, red, 80k, K&N, MAC cat back, MAC off-road X, Autometer Gauges, BBK Ceramic unequals, fully polished upper intake, fuel rails, and egr, working on installing.....MM full length subs, H&R sport springs, MM Lower control arms, MM caster camber plates, bilstein shocks, struts.

04-02-2003, 09:48 PM	#2
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	If your reffering to the gt-40 iron, like the heads that came factory on the 93-95 cobra, and early ford exploders, they arent a whole lot better, the valves are bigger 1.84 intake, 1.60 exhaust, i could be a little off on the exhaust size, the stock e7's have a 1.78 intake 1.46 exhaust, again i could be off on that, but it's close, i run the gt-40 heads, i had a mahcine shop port/polish, surface, and 3 angle valve job them, they say mine came off a 95 cobra, but the guy that sold them to me said they came off an explorer, but anyway, i can't tell you the performance they have since my car is still apart, i can let you know maybe monday, i should be threw. I also hear the 40's respond well to porting, and to notice a big difference from e7's you need to do at least a mild port job. __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

04-02-2003, 09:50 PM	#3
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	For starters GT40 heads have larger valves 1.84 intake and 1.54" exhaust valves. Also the port casting is much cleaner and smoother, plus the HUGE thermactor air injection bump is gone in the GT40 heads. Also they're faster burn heads because of a revised combustion chamber. I've heard that the aftermarket GT40 heads (cast iron) are supposed to add 30 horsepower to even a stock mustang GT. You can get used GT40 or GT40P heads for VERY cheap (the P heads were used on '96-'99? 5.0L explorers). GT40 heads were originally used on Cobra Mustangs and the 5.8L lightning and also sold through Ford Motorsport. __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

04-03-2003, 12:00 AM	#4
scale Registered Member Join Date: Mar 2000 Location: minneapolis, mn Posts: 158	do they just bolt right up? Any modifcation? Maybe i should do this since i am tearing my car down to the heads to put on my cobra intake anyway. __________________ 1991 LX coupe,AOD, red, 80k, K&N, MAC cat back, MAC off-road X, Autometer Gauges, BBK Ceramic unequals, fully polished upper intake, fuel rails, and egr, working on installing.....MM full length subs, H&R sport springs, MM Lower control arms, MM caster camber plates, bilstein shocks, struts.

04-03-2003, 12:35 AM	#5
NotchJohnson Registered Member Join Date: Oct 2001 Location: Florida Keys Posts: 593	Nope, they bolt right up no problem. Mine are ported to a 1250 intake gasket, and I dont remember what size exhaust. I forgot to get pics of them lined up against stock heads, but there is a big improvement in the exhaust ports. They till dont compare with most of the other aftermarket heads, but they are a decent improvement for cheap if you find a used pair. __________________ 89 notch-finally not stock!! ported gt40's, ported cobra intake, 65mm tb, 75mm maf, mac cai, lt's,prochamber, fms 1.6 rr, 125 shot.

04-03-2003, 02:11 AM	#6
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	My car ran a high of 104mph last year wit a ported set of GT-40's and a worn out Carter carb. They will be a big improvement over stock. __________________ 393W: AFR 205's, hydraulic roller, TKO600.

04-03-2003, 06:58 PM	#7
BLOCKER Registered Member Join Date: Mar 1999 Location: EDMONTON, Alberta, Canada Posts: 232	If you are going to buy a set of GT40s it is best to go private sale, all of the junk yards I have found know about the desire for GT40's for mustangers and are starting to charge an arm and a leg... __________________ -1988 MUSTANG COBRA GT (Canadian...eh!) -1987 Mustang LX coupe (2.3L) -1978 Harley Davidson FLH -2008 Harley Davidson Nightster 1200 -2008 Harley Davidson Night Rod Special -1997 Jaguar XK8 Convertable

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