GT40ish equivalent head options

[63A]

I'm rebuilding a 96 Explore engine for my Bronco and would like to replace the GT40 heads with a close equivalent aluminum head. I'm not looking for a performance upgrade - more just looking at cost of refurbishing high mile iron heads versus new aluminum heads. I know I will spend more to buy new alum heads versus refurb GT40 heads but I expect to offset some of that by selling GT40 heads. I know I will also need to likely buy new rockers/pushrods/guideplates/studs with aftermarket heads. I've looked at everything from the cheap $700 pair Chinese heads and the $900 -up heads at Summit/Jegs/Speedway/etc but would appreciate some insight from others who've already made this swap.

I plan to re-ring the shortblock (bores surprisingly good) and use the Exp cam.

What aftermarket alum heads are a close equivalent to the GT40 heads?

Thanks

 

[Timmy390]

IMO, AFR 165's are the close equal to the GT40's. I think the gains will be up high in the RPM band, Others will chime in I'm sure.

Again, JMO, Stock intake, stock cam, stock MAS, t-body and stock pistons I would stay stock heads. Maybe upgrade to GT40P's (smaller chamber size means more compression) as they're considered better than the GT40's but you then have to deal with the plug angle.....

Those cheap china GT40X (I think that's what they're still calling them) are good castings but have a rep about bad valves, guides and springs. Back several years ago, all the mustang buys were saying to get them bare and build them with good parts.

Tim

 

[63A]

Thanks Tim. I see GT40P heads for sale around here locally fairly often but would rather not deal with the spark plug hassle. I've got old Duff headers on it now that work fine but I thnk I'll mod a set of Mustang stock headers to fit to try to route the exhaust farther from the floor to reduce heat.

I know several folks running the Chinese heads (Ford and SBC) without problems but it only takes one bad valve to ruin your day. Are the actual (vs advertised) dimensions- CC, intake volume, etc - close to the GT40 heads (or GT40P)?

 

[63A]

I assume the stock Exp cam should minimizenegate chance of piston/valve interference issues with aftermarket heads but let me know if that is a bad assumption

 

[ntsqd]

I put AFR 165's on my 408 build, but it's still sitting in the garage. Typically can run more static CR in an aluminum cyl head than can be done with an iron head. The 408 was built to bump the low RPM power and to still pass emissions testing.

 

[Timmy390]

The china head issue was a while back so it might not be an issue now.....Which is a good thing.

Chamber size will fall in the below.....You would have to CC a set to get exact numbers. I don't remember what size my P's ended up being but I think it was on the smaller side vs the higher.
GT40 combustion chamber (63-66cc)
GT40P heads (58-61cc)
GT40 heads use a 1.54" exhaust valve
GT40P heads have a smaller 1.46" exhaust valve

I've not dealt with aftermarket heads on any of my build.....but always use clay to be sure if there is any question on clearance.

Tim

 

[Speedrdr]

I’m happy with the AFR heads on my 347 stroker. Engine seems to breathe a bit better…but that’s just “seat of the pants” judgement with zero science involved.

 

[73azbronco]

you really can't go wrong with a good valve job on gt40's if you only want aluminum, that does the same thing.

I went aluminum to scrape everything I could out of a 347. I saved about 100lbs all aluminum, which is about a tank of gas in weight. In a 5000lb truck, aluminum is not the solution unless thats what you are building for.

 

[ntsqd]

There are other reasons to go aluminum beside any weight savings. Higher SCR on pump fuel is why I went with them.

Are the seats in the GT40 heads induction hardened? If so, is it deep enough to take one valve job, or is it insert seats immediately?

 

[Bruners4]

My '97 Explorer 5.0 came with GT40P heads. I also wanted Alm heads but really didn't want the GT40P heads. I picked up a pair of the Blueprint Engines HP9009 heads. They have the bigger valves and flow almost the same as the AFR heads. I also installed the 1.73 roller rockers with the stock Explorer cam to keep it simple. Used 0,020 head gaskets to gain a little compression to help with the low-end power. I'm just about to 1k miles on it and it feels ok for mostly stock 5.0.

 

[73azbronco]

There are other reasons to go aluminum beside any weight savings. Higher SCR on pump fuel is why I went with them.

Are the seats in the GT40 heads induction hardened? If so, is it deep enough to take one valve job, or is it insert seats immediately?

Oh you bet, I was just simplifying seeing as it appeared there was no need for those benefits on his stock 302/5.0

 

[ntsqd]

If the budget is there, I'd do it just for the higher SCR.

 

[63A]

Thanks for all the info.

For clarification/confirmation - if I get aftermarket aluminum heads with 2.02/1,60 valves, will I have piston/valve interference issues using the stock Explorer cam and 1.6 rockers?

I'd like to avoid piston mods (enlarging eyebrows) or changing pistons

 

[jamesroney]

Thanks for all the info.

For clarification/confirmation - if I get aftermarket aluminum heads with 2.02/1,60 valves, will I have piston/valve interference issues using the stock Explorer cam and 1.6 rockers?

I'd like to avoid piston mods (enlarging eyebrows) or changing pistons

Yes.

I can confirm that the 2.02 valve in the Edelbrock Performer RPM Aluminum 60259 head is not compatible with the factory valve relief in the factory 5.0 HO piston.

I installed a set of those RPM heads on my 5.0 last year. You can see clearly how the diameter of the valve relief is sized for a smaller radius valve.

I can't guarantee that this is true for every aluminum head out there, but based on the wedge design, and the location of the valves...I'm going to say there are exactly zero 2.02/1.60 valves that will work with stock pistons in a 4 inch bore 8.2 deck Ford.

 

[ntsqd]

Poor man's piston notcher: braze a tool steel lathe bit to an old valve. Shape and sharpen the bit to have a radius on the tip and to cut the valve OD + whatever diametrical clearance you can live with. Insert in the correct valve guide in any cylinder. Slide a shaft collar onto the valve stem with a .05" gap to the top of the guide. Bolt the head on with this "valve" in place. You can guess what to do next. Iterate the collar to guide gap unto you have the notch depth where it needs to be. Take a measurement from the valve stem tip to the collar so that you can repeat this consistently.

No, I've never seen or heard of it being done.........

 

[63A]

Any thoughts on the Flo-Tek 203-505 (1.94/1.54, 58cc) heads? smaller chambers to bump CR a bit, smaller valves to eliminate piston/valve clearance issues, under $1K for a pair.

 

[ntsqd]

How do those sizes compare to the existing valves? < Unless they've moved the guide centerline in the head, that will answer the OD clearance part of the question.

For the depth part of the question it's harder to answer without a lay-up. If the OD will clear then the safest is to lay it up and do the old modeling clay test. This should be done anyway, just to be sure. If the OD won't clear, then there's no point in proceeding.

Yeah, I'm not ignoring that to test that cyl head that you have to own one or at least find one to borrow.

 

[73azbronco]

Hence my comment, stay gt40, no issues.

 

[ntsqd]

bleh!
You're no fun!

 

[Bruners4]

I checked my combination with modeling clay on both banks and had plenty of clearance with the 1.73 roller rockers and no head gasket (for checking only). I didn't record the clearance but was more than enough to not worry about it. Adding the 0.020 head gasket just added clearance.