GT40 heads: Are they worth it?

[happystang]

I've got a '95 5.0 in my stang, running an edelbrock rpm intake and Holley 600 carburetor.

All this is in my '66 mustang dressed up to look like an old 289. I dynoed the car and it put down 240 hp and 290ft/lb of torque to the wheels on a lean a/f ratio and stock rockers. Since then I upped the timing, went up a few jet sizes and added 1.7 ratio roller rockers from crane.

Let's say this is good for... 265 hp?

Anyways, are the gt40 heads worth going to the trouble of putting on? Ideally I'd like to get 300 hp to the wheel without touching the cam. What should I pay for used heads? What should I have done to them while they're off? As is the car is very quick with the t-5 and 3.80 gears, but of course more power is nice! And 300 is a nice round number

[My67Coupe]

Of topic but can you post pics. Curious how it looks disguised as an old 289.

[turbo2256b]

If your running E7 heads GT40s are a good move. Whats the lift on your cam

[Fastlane]

I don't think so unless you want to shave them down a bit. You will lose compression and negate a lot of the gain of the extra flow. Now if you get them shaved down you can make more power but you will have to take the intake in t o match them up.

Fast

[wheelsup351]

I think they're worth it. They aren't 60rwhp bolt ons on your setup. I've seen them used anywhere from 400 to 700. All depends who the seller is and what condition they are in. If they need a lot of work you might be out the price of a decent set of alum heads.

Gt40 heads are very good heads in many applications and they generally crap on e7s

[Fastlane]

Oh wait I did not see the 5.0 part. Yeah it would increase hp but you should think about changing out that cam for real change

[Baron7700]

im hoping to find some gt40 heads, not gt40p as they seem to need special headers to fit in vintage mustangs.

[Reverb]

You could shave them a bit to up the compression ratio - stock 5.0 is 9.0:1

[turbo2256b]

’93 Mustang Cobra…….......F3ZE-AA…………….....60-63cc
’94-’95 Mustang Cobra……..F4ZE-AA………….......60-63cc
’96-97 Explorer………………...F1ZE-AA………….......63-66cc

Think this is correct

[happystang]

Originally Posted by My67Coupe

Of topic but can you post pics. Curious how it looks disguised as an old 289.

In this photo it had a performer 289 manifold and edelbrock carb. Ditched both of those for a rpm intake and Holley 600.

I currently have the E7 heads, how much would a machine shop charge to mill the gt40 heads down a bit to bump up the compression? Wouldn't I have valve clearance issues and have to change the push rod length?

[bartl]

I've seen some flow number showing the E7's flowing in stock form a little better at lower valve lifts, like .200-.300 and, with some porting, E7's flowing as well as stock GT-40's. Maybe you could try working over your E7's first. If you're not satisfied you can do the switch to the GT-40's. As far as the milling is concerned I don't think you'll need to as the GT-40's combustion chamber is about the same size as the E7TE but if you did it would depend on how the valvetrain geometry lines up. You can use shims under some of the "bolt on" roller rockers out there.

[Renegade600]

GT-40 are a good bang for the buck... have the heads skimmed off some, clean up the exhaust ports, use your 1.7 rockers, and run the wheels off it....I would look for some F3ZE-AA heads from '93 as they will have the smallest chamber....I have (2) sets and both work out to be about 60cc..... the later ones seem to always have more volumn...
Tom

[turbo2256b]

E7 heads are 64cc give or take tollerance. The lightning truck heas would also have the smaller chambers.
Max differance of 2cc or even 6cc dosent realy change much in a low compression engine such as 9 to 1. Now if were a 12 to 1 compression it would be a big change.

[turbo2256b]

E7 heads flow about 145 CFM at .400 lift so do most small port Ford heads.
The GT40s flow about 185 CFM at .400 lift
At .500 lift most SBF small ports max 160 to 150 cfm. The GT40s around 190.

A performer RPM intakes flow maxes out around an average of good port bad port 167 CFM.
So at .4 lift you could see an increase of as much as 40 HP if all else is matched up and tuned properly

[ScottsGT]

They sell rocker arm shims to go on the pedestals if you shave the heads. Shave it .030, use .030 shims as an example.