GT40 Heads?

GT Drifter

New Member
Mar 26, 2003
Ontario, Canada
GT40 heads on a pretty much stock car, would there be a big difference? I know they flow better then the stockers.
I'm thinking about the GT40 'Turbo-Swirl' heads from Ford Racing. Any opinions on these?
I think with a GT-40 Intake manifold, heads and 1.6 roller rockers I should wake the car up a bit. :D
Also what long tube 1 5/8" headers will fit the GT40s?

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the heads will wake the car up if you go with a better intake like an explorer or cobra or sumthing besides stock.
you can run any kind of header with the gt-40 heads, they have the plug angle on those heads are the same as the stock heads, I would recommend, MAC,Hedman or cant go wrong with either ones... the gt-40p heads have a different plug angle...
GT Drifter said:
Some GT40 heads, intake and an E303 cam.
What about long tubes to fit the spark plug angle on the GT40 heads?

Kind of a dumb question, considering I drive a 5.0L but will those mods kill my gas mileage?

I'd say yes, especially since you are youing to be on the throttle more than before.

For the plug angle, that is only a problem on the GT-40P heads that came off the Explorers. The 'Turbo-Swirl' is different.

And for a cam, I think a custom cam would be much better. It will cost a bit more, but you will have better drivability, and more power. Give it some consideration.
GT Drifter said:
What about a B cam instead of the E? or will I fail emissions with it?

Also with all those mods should I get different injectors?

Hope this can answer some of your questions.

1st, you will fail emssions miserably with the Bcam.

I have mildly ported Gt-40 iron heads, with and anderson cam, explorer intake wih ported lower, longtubes, pulleys, 65mm TB, 73 mm mass air, and 24 lb injectors. I stepped up to the bigger injectors b/c I thought I would need them. Well...

Dyno'd at 289.9 RWHP and 329.6 RWHP and it was pig rich. I am having trouble getting the a/f ratio to 12.8-13.5. I am right about 12.0-12.2. Actually my milelage isn't as bad as I though it would be. About 25 miles to the tank less than what I was getting with the stock motor.
I have about the same setup, except tfs stage 1 cam, and i think it's great. I haven't dyno'd it yet, but it has alot more upper power, really kicks in above 2000 rpm. My a/f ratio is somewhat lean, and I have an AFPR on the way here now. Also, the gas mileage is around 9-11, depending on my foot. That will hopefully get better with the regulator. If you go with a custom/certain cam(s), your base circle may be smaller, requiring longer pushrods. I had my heads milled .025 and the geometry worked out good with the stock length. I don't know if they swirl gt40's are like mine, which are off of an explorer, but the compression is low, so milling them really a requirement. Good luck!
Hey I just got the z304 heads they flow 270 out of box flow numbers kill tfs and other heads damn close to r numbers i ditced the dart head idea for these . The tech guy at ford said those flow numbers are accurate regarding the assembled units, besides canfield was consulted by ford to help build these heads go for the z heads if your going to be adding a cam, intake and bigger exhaust more room to breath later on with more mods cost 1600 from summit ps go to ford racings website flow numbers are posted click crate engines then the 450hp 347 and then click on the link for the heads down the column here you find info.
yes im sure about the explorer intake having the same specs if not better then the gt-40, the problem (at least where i live) is trying to find an explorer with the 5.0 in a junk yard. but u can pick the intake up for less then $100 and the gt-40p heads off the same explorer for probly under $200
Be careful on the Explorer intakes - if you have to pass emissions ( egr), those built from early 97 models through 2000 (the ones that came with the P heads) do not have internal egr passages. You'll have to find a 95-early 97 intake to get the egr to work - and those are getting harder and harder to come by.
BTW - my set up includes the Y303 Ford Racing alum heads (flow about like a GT40P), 1.7's, Buddy Rawls mild custom cam (stock base circle, stock pushrod length), Explorer intake, 65mm t/b, 75 mm ProM, Ford Racing shorties, and an AutoLogic chip to turn off the egr and thermactor functions, up the idle speed a bit, richen up cold start, and alter the w.o.t. timing curve. Mine consistently gets 17-19mpg around town, and 24-26 mpg on the highway with 3.73 gears and shorter tires than the Stang (like a Stang with 3.91's).
I have the B cam, not a good daily driver or emmisions freindly cam at all. I wouldn't do the B cam again because it is a rough cam considering the power it makes. The E cam is a good all around cam. The stock cam isn't bad either, I had it on 1.7RR's and it performed well. The B cam hits hard around 3800rpm but I lost alot of bottom end.