GT 40 Head conversion

[65 fastback]

I picked up some GT-40 heads (not 40p heads) off of Craigs List and just want to make sure that I don't slip up any where. I'm going to pull my 351 heads and install the new heads.
I, also, picked up some Crane 1.7 Roller Rockers, pedestal mount.
I got a gasket set for a '68 302 from Summit.

Anything that I should be aware of or watch out for?

Thanks,
Tim

 

[96 DOHC Cobra]

It's definitely not a straight-forward swap. Unless those GT40 heads came off a 351W Lightning motor, you're going to have to drill out the head bolt holes to 1/2" diameter if you want to use them on a 351W. Installing them on a 302 wwill drop your compression a bit. Also, I think there's a mismatch on some water passages. You're supposed to drill the head or the block. I forget which.

 

[D.Hearne]

If you're going from the early Windsor heads to GT40's, there's hardly a difference there to justify the effort. Same valve/port sizes for both. The GT40 chambers are about 4 ccs bigger.

 

[65 fastback]

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[65 fastback]

The 351 heads I'm removing, arnt' the early heads, so hopefully I am gaining something with the GT-40 heads and 1.7 full roller rockers.

I'm installing them on a '68 302 block - do I still need to drill out any water passages? Can anyone point me to a link that can explain exactly what I will need to do?

Thanks for any help,
Tim

 

[Fast63]

It's definitely not a straight-forward swap. Unless those GT40 heads came off a 351W Lightning motor, you're going to have to drill out the head bolt holes to 1/2" diameter if you want to use them on a 351W.

You're installing on a 302, so there is no need to drill out the head bolt holes.

 

[65 fastback]

What about the water passages? Do I need to do anything to align the water passages? I thought this was a direct swap onto an early model 289/302.

Thanks,
Tim

 

[D.Hearne]

What 351 heads do you have now ?

 

[shelbe67]

on the older 289's i believe a hole needed to be drilled out as they didnt have it but when the switched over to the 302's they had them so i believe you should be ok

 

[65 fastback]

Thanks Shelbe67.

D.Hearne - I'm not sure what year they are. Where should I look to ID them?

Thanks,
Tim

 

[D.Hearne]

Thanks Shelbe67.

D.Hearne - I'm not sure what year they are. Where should I look to ID them?

Thanks,
Tim

Look at the date code in the rocker valley. That'll tell you the exact date. Another way to generalize it is the number of intake bolt holes and the shape of the coolant ports on the intake side. Up untill about 1975, the coolant ports on the intake side are "L" shaped, with an extra intake bolt in the port.

 

[65 fastback]

Back from the dead.

The heads that I took off are 351W:
D80E AB
The markings inside the rocker valley are:
3 WC/P 77 3A20

They were rebuilt about 20K miles ago
with hardened valve seats and a 3 angle valve job
They also have Comp Cams Valve Springs - 942

Are these heads worth anything?

Tim

 

[D.Hearne]

Back from the dead.

The heads that I took off are 351W:
D80E AB
The markings inside the rocker valley are:
3 WC/P 77 3A20

They were rebuilt about 20K miles ago
with hardened valve seats and a 3 angle valve job
They also have Comp Cams Valve Springs - 942

Are these heads worth anything?

Tim

Aside from the valve springs? They're know to make dandy boat anchors. The chambers are huge at 70 cc's. The 3A20 says they're 1983 heads.

 

[mr_woodster]

Im pretty sure they are close to "bolt on" as you can get. Easiest way to check is to set the new headgasket on the GT40 head and see if it all lines up. If so, pretty simple. After that, its proper push rod lenghts and valve cover clearance.

 

[Rusty67]

Wouldn't the D80E code indicate 1978 or is that the first year that part was made and the AB is the revision on that part ?

 

[phutch11]

You really need to check PV clearance especially if you know that the GTs have been shaved. Ask me how I know.

Additionally, despite what everyone says you may have header issues with the spark plug...again, ask me how I know.

I don't think you'll be terribly impressed with the GTs - I'm not. Unless the heads are ready to go with no work needed, I'd sell both sets and go get some Edel's or patroits and make some real power.

Good luck

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[Decurion]

patroits and make some real power.

The gt40 heads (non-P) have the same plug angle as the old heads. I have a set on my car, and no clearance issues. They flow about the same as the 69/70 W heads, but just simple bowl blending in the intake and opening up the exhaust all the way through will make a world of difference. The combustion chambers are big, but the 93 Cobras were milled .030", so you could do at least that much to help with compression, depending what pistons you have. Also, these heads pretty much stop flowing by .500" lift, so keep that in mind in regards to your cam.

 

[SadbutTrue]

I picked up some GT-40 heads (not 40p heads) off of Craigs List and just want to make sure that I don't slip up any where. I'm going to pull my 351 heads and install the new heads.
I, also, picked up some Crane 1.7 Roller Rockers, pedestal mount.
I got a gasket set for a '68 302 from Summit.

Anything that I should be aware of or watch out for?

Thanks,
Tim

edit: nm

I do recommend you consider milling the heads down to compensate for lost compression. I did .020" on mine, should yield about a half-point CR boost without compromising anything.

 

[D.Hearne]

Wouldn't the D80E code indicate 1978 or is that the first year that part was made and the AB is the revision on that part ?

The D8 only indicates the first model year it was produced. So a D8 part could have gone into production in late 77. Ford used the same Engineering prefix for years in some cases. Like the C8 302 rods, these were used untill the early 90's. Ditto for the E7TE heads, the last year would have been 1997 in the F & E series line.