I have a 78' thats been in the family since 80' or so. About 10-12 years ago we dumped some money into it to make it a reliable daily driver. There wasnt a whole lot of options being we lived in California and the vehicle is under emissions controls there still.

Now i live in a state without emissions controls and want to update the engine...leading to a few questions.

I know the internals of this engine are in good shape. We had the engine "re-manufactured" 10-12 years ago, which included a full tear down (inspecting of the block for cracks etc all the basics) as well as Being balanced and blueprinted. The only thing not to stock specs would be the cam. He installed an RV cam which also changed the firing order on this 302 to that of a 302 HO or 351. The claim for this is more "balanced" firing order not really any noticeable power gains. The springs are supposed to be a little more stiff than stock as well to go along with the cam.

My list of things to do. Not in order.
-replace intake and autolite 2150 carb with an aluminium intake and 4bbl carb.
-replace duraspark 2 ignition (ignition modual pretty finicky in the desert heat) with Davis Unified Ignition from performance distributors
-long tube headers to a true dual exhaust
-gt40 heads off a 96 or so explorer (i want to do this first, or at least with the intake and carb)

My questions are regarding just the gt40 head swap.

I know they are a direct fit in regards to bolting them on. But nobody ever mentions the valvtrain when doing this upgrade. I know they were made with roller cam set ups including different rocker arms and stiffer springs, so Can i swap over my valvetrain into these heads to take advantage of the better flow and compression. Or do i need to replace anything? The rockers from the 96 are for roller cam set ups, do the rockers from the 78 bolt into the gt40s? Buy a new set of rocker arms? Longer or shorter push rods?

Thanks for reading and or helping out.

 

...bumping...

Any help?

 

I kept the GT40 rockers, got new pushrods and valve springs but I also shaved the heads and installed a new cam.

 

Changed the firing order with the cam?

 

Not sure, haven't made it that far yet. Engine is on a stand, not broke in yet.

 

Rockers shouldn't much matter. As long as your '78 302 has the pedestal-mounted rockers, I think they're all the same from '77 all the way up to '99 or whenever.
You'll probably need new valve springs. I've never heard of anyone using the OEM Explorer springs on a flat tappet cam, but who knows, they might be just right... You might need to measure for new push-rods if your 302's block and heads have been machined, (because it will be using a non-stock length pushrod) but if you have the GT40s machined identically, the 302's existing push rods should work.

I put some GT40Ps on my Mustang. I literally pulled them off of the Mountaineer at You-Pull-&-Pray, and did nothing more than drop in a set of Alex's valve springs, (for the Mustang's roller-cam engine) and I drilled Secondary Air passages to each rearmost exhaust port and drilled and tapped holes for the Air tube's bolts, so as to not elicit the codes 44 and 94 which indicate no Upstream Secondary Air.

These heads definitely made differences which I could feel. They gave me more torque down low which I noticed when taking off, and also a little bit stronger pull at Wide Open Throttle - not to mention a deeper and slightly louder sound at WOT...

So you will need new springs and push rods, but the rest of your stuff 'should' work.

 

Thank you for the detailed response. I appreciate it.

 

I am following along to see how this goes. What kind of HP/torque are you looking at?