can anyone tell me anything about gt40 and gt40-p heads?
what is so good about them or bad about them?
what makes them different from other heads?
also what cc are they?

 

They are cast iron small block ford heads. The GT-40 "P" is the high performance version with larger valves, and better air flow (basically ported and polished) They are good inexpensive heads. They are probably some of the best you can get for the price. They cost about 1/3 as much as aluminum heads.

-Jon

 

The GT40's also came in aluminum versions, and are sold through the Ford SVO Performance Parts catalog. As mentioned, they are a very popular head and have a very good reputation as a power builder on both the 302's and 351W's. Even better, Ford sent some production vehicles off the line with them, including the Mustang Cobra's and the Lightning trucks. When the Explorer was offered with the 302, Ford chose a higher-flowing cast iron version of the GT40, designated as the GT40P, for use in the application. The great thing about the GT40's and GT40P's (besides their performance) is their availability...... having been produced for assembly-line vehicles, there are many on the market, which translates into a strong aftermarket and lower prices. Here are a couple of sites to visit for more information on them: www.corral.net/tech/head_tech_4.html, http://ratnin.home.mindspring.com/headid.htm, and www.dayton50perf.com/heads.html.

 

>They are cast iron small block ford heads. The GT-40 "P" is
>the high performance version with larger valves, and better
>air flow (basically ported and polished) They are good
>inexpensive heads. They are probably some of the best you
>can get for the price. They cost about 1/3 as much as
>aluminum heads.
>
>-Jon


Not exactly!!!!


The GT-40 Irons were available on the early lightning and 5.0 Cobras. They run a 1.84 intake and 1.54 exhaust valve. They use all standard manifold or headers available to the 5.0.

The "p"'s(used on the later 5.0 explorers) actually have a SMALLER exhaust valve but due to some minor exhaust port CASTING (there is no porting or polishing as delivered)flow the same as the standard GT-40's. The P's have a relocatd spark plug location that makes header selection a tad more difficult(even though I've made p's work with standard FMS headers with a home made tool)

Because of the spark plug location on the GT40 P heads there is a small boss in the chamber which makes the P about 2CC smaller than the GT40. This gives the P a tad more compression. P's DO NOT have the smog air hole but can be drilled easily.

Both heads can be worked to pretty close the same (The P has a slight exhaust flow advantage especially when using same size valves)
but the P has the smaller chamber for more compression.

The P's are very cheap but remember the header hassle and they both must be machined to use stud mount rockers.

The aluminum GT-40's share the name(there's an X and Y version) but are different heads.

We all live and learn and I've made a few mistakes. One of them was building some P heads with 1.9/1.6 valves having them ported and flowed, using good hardware and spending $1200 to get the the same flow #'s (230/170) as a pair of $995 aluminum TFS heads which wouldn't have had the header hassle. They are both good as delivered but don't expect a fire breather out of the box.( 5.0 Cobra and 5.8 Lightning were in the 240 HP range and the Explorer with P's was 210 with a lot less cam)

 

From what I have read TRICK FLOW has about the best heads complete for the 351

 

GT-40 Irons are very good street heads, provide good torque and with the help of 8lbs of boost helped propel my 94 Lightning to 13.4 ET's. I feel this is quite a feat for a truck with aerodynamics of a brick.
This winter, I purchased a slightly used set of GT-40X from a mustanger that decided to step up to a set of Canfields. When I received them, I had them flowed at 240 CFM at .5 lift on the intakes and 160 cfm at .5 lift on the exhausts. These heads already had the bowls cleaned up and all the casting flash out of the ports, basically a stage 1 cleanup. We went to work on the exhaust seat and short radius on the exhaust port and 3 angled the valve etc. and finished up with exhaust flows of 179cfm's at 28" of water. All this off 1.94 and 1.54 valve sizes. I'm looking forward to installing shortly, then I will have a low mileage set of GT-40 irons for sale to someone. For the same money I could of bought a set of AFR's with a little better flow to them but wanted the reliability factor of a Ford made head.
Later
Steve

 

Let me know when you'll be ready to sell the heads and how much you'd like for them. Thanks!

Zane
zwr14(No Email Addresses In Posts!)

 

I have a set of TFS aluminum O-ringed heads with 25,000 daily driver miles (no racing). Be cautioned about the cam lift. Summit Racing tech told me that the TFS heads could handle that much lift (.533). I ended up with a broken valve spring. TFS tech told me later that .533 was to much lift for the springs. When I took them to the shop for a check, I had to replace all exhaust valves (galled stems), all valve guides and springs (CompCams 986). They flow good but be leary about the cam lift. I was lucky that the keepers put a "burr" on the valve stem and that was the only thing that kept the 2.02 valve from being lunch for the piston.

 

Greetings, all! Just wanted to add/contribute something on the GT-40P heads that (so far) no one has really explained here. Alot of people know that the GT40P heads have a problem bolting headers on (interference) but no one says why. I'd like to tell you. When the particular team of Ford engineers responsible for the GT40P's were designing this head, the ultimate goal put before them was to design a 5.0 head that would produce very low emmissions and still make power. What they came up with was, as it turned out, simply relocating the spark plug (as well as revising the exhaust port for better flow). Moving the spark plug is one thing, but they also revised the ANGLE of the spark plug. In other words, the spark plug now ends up closer to where the header tubes exit the head, causing interference. To combat this problem, they made shorter spark plugs for more clearance. Most aftermarket headers will work with the shorter plugs and the right wires. In some cases, a small dent or dimple in a header tube may be necessary. (this is to clear the WIRE, not the short spark plug. Keeps the wire from burning/shorting against the header tube)
The newly designed head actually makes it additional power not so much due to a better breathing design, but because the combustion chamber is much more efficient. The emmissions were so much lower now (due to a more complete burn) that Ford actually awarded the Engineering team for their design. That "more complete burn" means more power. Hope this helps some. - Don

 

These shorter plugs are new to me. How do I get some? Who makes them and what do I ask for at the auto parts store?

many thanks,

Kyle Dean
Dallas,TX

 

Gt40-p are hard to find but i will sell you a set for like $750 can
and a months rent

 

Kyle,
Ask for plugs for late model Explorers with the 5.0L. Lot's of people buy the heads new, they never see them installed on an Explorer. As I recall, the short plugs cost a little more, but they save a lot of grief. Also, depending on what headers you are using, a set of plug wires with either 90-degree or 45-degree boots will work best. You may even want a set of "universals" so you can route them appropriately. As for the heads flow potential, I personally have ported/flowed my heads to 238 cfm at only .430 lift. I was initially looking for 225-230 cfm to match a GT40 FI Intake flow rate, but ended up better than I thought AND at a lower lift. This translates into high-velocity (a good thing), meaning I don't need some radical cam to make torque and HP. The engine should live a lot longer this way. But, keep in mind, I did upgrade the valve sizing to 1.95 on the intake and 1.60 on the exhaust. And, for those interested, I tested a few different valves with these heads on my flowbench and found that the "under-cut" valves resulted in ZERO cfm gains. Yes, ZERO, so stock-type configuration valves will work just fine. - Don

 

Hey it looks like some of you have some experience with the gt40p heads, it would be great if you could answer a question for me. Have any of you ever installed a cast, factory style exhaust manifold on these heads? Is the factory Explorer manifold any good as far as flow goes? How about 289 K-code exhaust manifolds, think these could work on gt40ps?

Neal

 

Neal,
The factory Explorer/GT40P "manifolds" are actually tubular headers. They have a rather unique design, reminiscent of a "ram's horn" design. The tubes sweep up to a degree, giving additional clearance for the spark plugs. As for bolting on earlier stock-type manifolds? That is an interesting question, something I may be able to try for you, but I have to find an early set of manifolds first. I have new GT40P heads that I have been working on, bigger valves, port work, etc. If I run across some manifolds, I will post the "fitment" results. - Don

 

GT 40 p heads will deinately pck you up over stock Ford heads, but you gotta know that aftermarket heads are much better. Get a set of World's Windor Jr Heads, or the ultimate, the Roush 200. Remember, it's not just about flow, it's about tumble port velocity, which is where monster low end torque is made. Build a motor to make MAx low end/midrange, and the high RPM power will come. Even the SVO Tech in Dearborn MI told me that the Windsor Jr's are better than anything they offer, and they're only about $800/pair at Jeg's, and they already are drilled for both small and big tube headers. Besides, World's Iron foundry casts denser, better iron, with fewer imperfections to clean up. I have a set, but havn't bolted them onto my '77 F100 yet, but I'll keep you posted on my results, look for my 302 powered Dinosaur at The atlanta fun ford weekend, April 19-21
Thanks and happy wrenching, John
ps, someone please inform me on how to post pictures with this message