GT40 heads
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Elder User
Joined: Jul 2011
Posts: 609
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From: Stockholm, NJ
GT40 heads
I have a 1978 F250 4X4 with a 1984 351W in it. Engine runs fine (I replaced the timing chain last summer and put on a Typhoon intake with an Edelbrock carb). I'd like to make a bit more power and it seems like a set of GT40 heads and a 260 duration cam would wake things up at a relatively low cost. I see some GT40s available locally, but none of them have rocker arms. Could I use the rockers off my heads, or just buy a new set, and what ratio works best. Truck is 4 speed (NP435) with 3.54 gears.
Thanks
Frank
PS - what is a good number to pay for a set of GT40 heads that have not been freshened up?
Thanks
Frank
PS - what is a good number to pay for a set of GT40 heads that have not been freshened up?
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
Yes the rockers you have will fit the GT40s, and those will be 1.6 rockers. For a cam I'd suggest something like the Comp 35-234-3 or 35-238-3. The heads should bump CR up from 8.3 to 8.8:1 and also increase potential airflow by a good 30%, and either one of those cams will provide substantial gains across the board over the stock bumpstick. Combine these parts with headers and a free flowing exhaust and you should have close to double stock HP and 50% more Tq.
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Elder User
Joined: Jul 2011
Posts: 609
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From: Stockholm, NJ
Thanks! There is already a set of headers on the motor with a full dual exhaust. I noticed that the headers have seen better days, but none of the header manufacturers list headers for a 351W in a '78. I realize that these trucks never came with that motor, but was wondering what headers would fit? Would ones for a 302 work?
Thanks!
Thanks!
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Thanks! There is already a set of headers on the motor with a full dual exhaust. I noticed that the headers have seen better days, but none of the header manufacturers list headers for a 351W in a '78. I realize that these trucks never came with that motor, but was wondering what headers would fit? Would ones for a 302 work?
Thanks!
Thanks!
Senior User
Joined: Nov 2010
Posts: 165
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From: Lincoln, Ca
What I paid -
I paid $175.00/pair that were taken off a Pick-N-Pull vehicle. Pick-N-Pull (a local junk yard where you pull your own parts) wants around $100 for a set if you can find them and then pull yourself.
Joe
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From: BC Cana'duh
Boss Fan be careful of which headers you buy.The truck headers listed for '80s 4x4's passenger side fit,but the drivers side will probably hit the rear of the front diff/driveshaft area.I've tried two different sets,one was hedman,the other was flowtech.The tubes come down and bend at a 90 degree angle and contact either the diff or driveshaft.I have an '83 E150 with a '78-79 bronco front suspension with a dana 44.I think the 3/4 ton front diff is similar to the half ton.I run shorty unequal length stainless on a 351W.I would love to get some longtubes but I can't keep buying headers that don't fit.It looks like a set from an earlier Mustang ('65-69) might fit,but until I can find a used set locally,it'll have to wait.The drivers side tubes have to come down at more of an angle(about 35-45 degrees) to clear the diff.
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Thread Starter
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Elder User
Joined: Jul 2011
Posts: 609
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From: Stockholm, NJ
Thanks everybody! And I am correct that it is the GT40 heads that are a direct bolt on (once you bore out the head bolt holes to 1/2") and that the GT40P heads have figment issues?
Thanks
Frank
Thanks
Frank
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
And yes, you're otherwise correct 
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Yes, the aluminum GT40 heads generally produce more power than the iron heads.
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