gt40 heads

JT929240 · Aug 11, 2010

So i am almost done with putting my 302 together and i had bought some gt40 heads off a mustang forum for $400 then when my mechanic got them he said the guy had put bigger valves in without seating them so i had to bring them to a machine shop and that cost me $500 so i was not too happy with that...Then on top of all this i call a shop that just does mustangs to see how much to tune my car when its all done because i have a v-1 strim i am putting on it

and the guy says what are you running..I tell him everything and he says oh those heads are not that good and practically no one is using them anymore...WTF..so did i just spend $900 on heads that are crap? Oh and they are the steel heads not aluminum not sure if the gt40 or gt40p all i know is that i had to buy bolts that came with sleeves to reduce the whole on the heads so maybe they were off an explorer?

CDQICKGT · Aug 11, 2010

Ouch... They are out dated heads but are still decent. For about 200$ more you could had a damn nice set of aluminum heads though.

JT929240 · Aug 11, 2010

yea i saw that and thats exactly what i said for 200 more i could of had aluminum WTF..this sucks...so why are these heads so bad?

Mustang5L5 · Aug 11, 2010

They aren't bad. They are a good budget head. Plenty of guys run them.

I helped a buddy put together a stout gt40p setup only to have a shop owner put the entire car down because of it....so we went to another shop where the guy was more than happy to help us dyno tune the car. Not everyone can afford a 10k engine.

JT929240 · Aug 11, 2010

so i can still get some good hp out of them?

Mustang5L5 · Aug 11, 2010

Well, do yup have the regular or the 40p?

The gt40 will say "gt" in the rocker valley. Stock valves are 1.84/1.54

The gt40p will say "gtp" in the rocker valley. Stock valves are 1.84/1.46

If yours have larger valves...it might help. Can you measure the valves?

Guys typically make 270-300 rwhp doing their homework with these heads. There is a slight compression bump depending on which head you have and if they are milled

2000xp8 · Aug 12, 2010

$500 at the machine shop is a hefty bill if you provided all the parts.
What exactly did they do for that much money?

IMO, the most you invest in a set of gt40 iron heads is $250 for the heads, and maybe another $250 in a valve job.

As far as guys not using them anymore, it's kinda different with a shop.
Shop owners aren't using them.
But backyard enthusiasts on a budget are.

JT929240 · Aug 12, 2010

i think i mixed it up i had the crank balance with all the pistons and rods i think that was what he charged $500 for the heads i think were $200...but they do have bigger valves and heaver springs on them i think the guy before tried to get more power out of them but screwed it up because my mechanic said they probably ran like crap since the new valves were bigger and not seated....The other thing with these heads is it was impossible to get the right spark plug i went to autozone they gave me the wrong plugs the guy at the mustang shop said of course oh we dont carry them but gave me the part number and autozone still gave me the wrong plugs..i called cj ponyparts and the guycould not figure it out i told them they are gt40 heads and i need to run a plug one colder than oem because thats what vortech reccommends and he said i have to reaserch to find out what plug to use because they don't know so then i called summit tech line and tell the guy and he seemed like he knew what i had and what plug i needed so i ordered them i hope they fit......

Cutter1024 · Aug 12, 2010

So with a mild motor, how much rwhp can you see from swapping the E7 heads for a pair of GT40p?

I found a pair that have 46k miles on them for $200. Good deal? They are local too.

Mustang5L5 · Aug 12, 2010

JT929240 said:
i think i mixed it up i had the crank balance with all the pistons and rods i think that was what he charged $500 for the heads i think were $200...but they do have bigger valves and heaver springs on them i think the guy before tried to get more power out of them but screwed it up because my mechanic said they probably ran like crap since the new valves were bigger and not seated....The other thing with these heads is it was impossible to get the right spark plug i went to autozone they gave me the wrong plugs the guy at the mustang shop said of course oh we dont carry them but gave me the part number and autozone still gave me the wrong plugs..i called cj ponyparts and the guycould not figure it out i told them they are gt40 heads and i need to run a plug one colder than oem because thats what vortech reccommends and he said i have to reaserch to find out what plug to use because they don't know so then i called summit tech line and tell the guy and he seemed like he knew what i had and what plug i needed so i ordered them i hope they fit......

They are 93 cobra plugs.

Of course, if you could id the head we could give more info. What is written in the rocker valley?

BYRDPE · Aug 12, 2010

autolite 763 is one step colder for the gt40 heads.

Mustang5L5 · Aug 12, 2010

Cutter1024 said:
So with a mild motor, how much rwhp can you see from swapping the E7 heads for a pair of GT40p?

I found a pair that have 46k miles on them for $200. Good deal? They are local too.

Depends on a lot of factors really. Stock cam? Stock intake? I guess I'd say you would gain 20 rwhp with them.....but a matched combo might give more.

There is a thread here called the 300'rwhp gt40p thread or something....where guys were shooting for 300 rwhp with these heads. It's not typical, but can be done. A lot of gt40p hci setups I have seen have been anywhere from 270-300 rwhp.

Going rate for 40ps these days is 200-250.... Cheaper if you go to the junkyard yourself .

JT929240 · Aug 12, 2010

they are gt40 not 40p and i have an e-cam and aluminum performance rocker arms so if i can get 300 just off the motor with the v-1 strim it should bring me up to at least 400hp right? oh and i have a cobra intake on it..So what heads are the better ones gt40 or gt40p

v8only · Aug 13, 2010

gt40 and gt40p heads are so close in performance, it doesn't really make a difference....the gt40's however are a lot easier to port if you go that route.

gt40 and p heads are probably hands down the most common upgrade in the mustang hobby. However, it is a budget head swap. Aluminum heads will get a good deal more hp...but who cares right? you're already committed to these heads.

expect to make maybe 275 at the wheels give or take n/a...since you have larger valves...then add the s trim...

phutch11 · Aug 13, 2010

Let me tell you about my "budget" gt40 heads...

250 to buy them
200 to mill, valve job, valve guides, and replace some bent valves
100 for new springs
75 for gaskets

First time out bend two valves in each head because i ran at the minimum safe PV clearance you hear everyone quote. Its safe as long as your valves don't float.

200 to repair damaged valves and guides
75 for custom length pushrods
150 for new 1.6 rockers
150 for stud mount conversion kit
75 for more gaskets
Oh yeah, and as it turns out, while my heads have all the external GT40 markings, it turns out that they have the P plug angle and my old headers wouldn't work.

Save your money for new heads.

Make damn sure you check PV clearance with those heads especially if they were milled and with the larger valves.

What ratio are your rockers? If they are 1.7 you are probably in for trouble.

And check it at every cylinder.

Good luck...

BYRDPE · Aug 13, 2010

^ wow...i woulda cut my losses.

JT929240 · Aug 13, 2010

i have a new set of k\b pistons from summit racing in the block so i hope there is enough pv clearance because my mechanic has already put the motor together he just has to drop it in now..How hard will it be to check it now i would have to buy new gaskets because he would have to take the head back off to check the clearance right?

2000xp8 · Aug 13, 2010

I would hope your mechanic checked.
If not, you need a new mechanic.
No real engine builder just slaps parts together on the word of a customer, unless of course they like headaches.

JT929240 · Aug 13, 2010

Lol...yea your right i'm gonna ask him if he checked the pv clearance before he starts it up..

JT929240 · Aug 14, 2010

As far as the spark plugs the tech guy at summit sold me autolite AR103 plugs and my mechanic said they fit so i hope they work??

gt40 heads

JT929240

New Member

CDQICKGT

New Member

JT929240

New Member

Mustang5L5

That is…until I whipped out my Bissell

JT929240

New Member

Mustang5L5

That is…until I whipped out my Bissell

2000xp8

JT929240

New Member

Cutter1024

Member

Mustang5L5

That is…until I whipped out my Bissell

BYRDPE

Mustang5L5

That is…until I whipped out my Bissell

JT929240

New Member

v8only

Active Member

phutch11

Member

BYRDPE

JT929240

New Member

2000xp8

JT929240

New Member

JT929240

New Member

Similar threads

gt40 heads

New Member

New Member

New Member

That is…until I whipped out my Bissell

New Member

That is…until I whipped out my Bissell

New Member

Member

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

New Member

Active Member

Member

New Member

New Member

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency