Finalized GT40P headswap, initial thoughts

TomCat · Apr 23, 2007

Yup, got everything done today and after about an hour of timing, putting fluids back in and making sure there were no leaks, took her for a spin and let me say WOW. I can't believe what a difference it makes to have a nice(er) set of heads on these cars. I'm just stoked, so I had to tell somebody lol. My friends don't appreciate it fully
Here's what I added anyhow:
Went from blah E7s to a set of 40Ps, obviously, TFS dual springs, new pushrods, 1.7RRs and the 70mm MAF. On the old heads the top end felt really slushy and like power would die off where my stock tach read 4,800. Not anymore! Still haven't gotten on it too much, since I'm kinda paranoid that it will develop a lower intake coolant leak. After some more inspecting, I'll take her out again.
Anyhow, the whole swap went pretty damn well! I really didn't run into any problems, didn't spend much money at all, and the actual labor wasn't so bad... so anyone still on E7s (excluding the ported ones, of course) should run to the JY and pick some of these badboys up! They rock.

25thmustang · Apr 23, 2007

Ill stick with E7s, thanks...

J/K we have a GT40P car and it does pull good. Those heads probably helped low end, and made the car feel a lot better on the street!

Mr. Rustypwnz · Apr 23, 2007

youll love the change!!! it feels way stronger from 3-6k, mine likes to spin now and revs fast!!!

85_SS_302_Coupe · Apr 23, 2007

I have some really cool head news on the way.....stay tuned

On and congrats on the Ps, they are some badass stock heads.

1985 5.0 · Apr 23, 2007

These heads come stock on the Cobras???? would a set work on my carburated 85??

MAC'n89Blckstng · Apr 23, 2007

I had the same exact reaction when I put my gt40's and Explorer Intake on my car to help the existing e303 cam. And then I put the big mass air on it wow. I can actually pedal out first, makes the hard acceleration sound awesome. Did these heads change the sound of your car at all? Mine got 4 times raspier. Congrats on the install, just think what a set of AFR's would do to our cars.

85_SS_302_Coupe · Apr 23, 2007

1985 5.0 said:
These heads come stock on the Cobras???? would a set work on my carburated 85??

GT40's came on the '93 Cobra, GT40P's came on later 5.0s, commonly found on '98+ 302 Explorers. And yes they will work on your '85, i was going to use them on mine but i have other heads now.

Strippt88 · Apr 23, 2007

Block's the same, aughta be fine on the 85.

BLOWN 5.0 FOX · Apr 23, 2007

im not too keen on the four eye models but I heard piston to valve clearance on bigger valved heads were sketchy prior to 86...just a half thought, check into it.

1985 5.0 · Apr 23, 2007

85_SS_302_Coupe said:
GT40's came on the '93 Cobra, GT40P's came on later 5.0s, commonly found on '98+ 302 Explorers. And yes they will work on your '85, i was going to use them on mine but i have other heads now.

thanks for the info

BLOWN 5.0 FOX said:
im not too keen on the four eye models but I heard piston to valve clearance on bigger valved heads were sketchy prior to 86...just a half thought, check into it.

i thought the 86 was the only year with the piston to valve clearance issue

85_SS_302_Coupe · Apr 23, 2007

Yes, the '86 has no valve reliefs on the pistons....BUT, it's always a good idea to check clearance anyways.

TomCat · Apr 23, 2007

MAC'n89Blckstng said:
I had the same exact reaction when I put my gt40's and Explorer Intake on my car to help the existing e303 cam. And then I put the big mass air on it wow. I can actually pedal out first, makes the hard acceleration sound awesome. Did these heads change the sound of your car at all? Mine got 4 times raspier. Congrats on the install, just think what a set of AFR's would do to our cars.

Yeah man, it really seems like it. My bro came out and said it sounded different, too. lol, now I'm kinda thinking... damn, shoulda waited and got some AFRs. Oh well, gotta build the car with what money I have
Oh and if anyone is wondering, MAC shorties will work but the #4 plug won't fit without dimpling the pipes... and I stuck a heat shield on there too for good measure.

madspeed · Apr 24, 2007

pretty nice heads for the dough. i had em too. see times in sig!

TomCat · Apr 24, 2007

Right on, more info on your mods at the time? I'd love to hit 11s, but it's so not happening... probably not even 13s, lol.

BigHairyMonkey · Apr 24, 2007

^you should MOST def be DEEP in the 13s with some Ps

madspeed · Apr 25, 2007

i had pretty much all the bolt ons. was running 13.10's at 105 without the 150 shot

25thmustang · Apr 25, 2007

Our 40P car was going 12.00s (on a warm crappy track day) and did go 7.48 (11.7 or so) into a headwind (the reason Etown was shut down to 1/8th passes only). It had a race set up chassis and such, but the motor was very simple. Stock rering on the bottem end, GT40Ps, milled to 58cc, 1.84/1.54 valves with VJ, 1.7 rockers, stock cam, 4 degrees back, Cobra intake, 70mm TB, 76mm MAF, 24 lb inj., K&N in the stock box, underdrives, FMS shorties, Prochamber, and Hooker mufflers out tailpipes. The chassis planted the power, and it didnt have smog, AC or anything of the sorts, but the motor is now in my brothers 86 street car. Were expecting mid 12s out of it (the 3.55s are going to kill it, the old car had 4.30s, but went 12.1 with 4.10s).

Dont be discouraged, the heads arent a $1000 AL piece, but for the money they are great and can be made to run hard! Just ask the right questions, run the right combo, and drive the piss out of it!

TomCat · Apr 25, 2007

Awesome, now I'm all exicted to get it out to the track. I think my next couple paychecks will be going into to chassis stiffening and the like.
Thanks for the responses guys

Finalized GT40P headswap, initial thoughts

TomCat

New Member

25thmustang

Mustang Master

Mr. Rustypwnz

Advanced Member

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

1985 5.0

New Member

MAC'n89Blckstng

Active Member

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

Strippt88

New Member

BLOWN 5.0 FOX

Member

1985 5.0

New Member

85_SS_302_Coupe

it sucks (I know) to be on the receiving end

TomCat

New Member

madspeed

Colonel Mustard

TomCat

New Member

BigHairyMonkey

madspeed

Colonel Mustard

25thmustang

Mustang Master

TomCat

New Member

Similar threads

Finalized GT40P headswap, initial thoughts

New Member

Mustang Master

Advanced Member

it sucks (I know) to be on the receiving end

New Member

Active Member

it sucks (I know) to be on the receiving end

New Member

Member

New Member

it sucks (I know) to be on the receiving end

New Member

Colonel Mustard

New Member

Colonel Mustard

Mustang Master

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency