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GT-40(or stock) Heads Swap

39712 Views 28 Replies 16 Participants Last post by  Saint_Bronco
Because I have searched and searched and still ran into questions while I did my gt-40 head swap, I figured i would post a write up on how I did it.

I am 19 years old and have little experience with engine work. Anyone who does, feel free to correct me or participate in this write up.

I have a 1988 f150 302. The previous owner had a cylinder blow because of a clogged cat. This motor is sapose to be a "brand" new motor from Ford(with new fuel injectors) now at 50,000 miles. I bought the truck with 20,000 and started noticing when on a steep uphill grade at 55 mph the truck would start bucking(this is around 40,000 miles) eventually it got to be where it bucked when idoling, and you could hear the missing which sounded like a bad exhaust leak.. I had manually checked all the sensors I could myself, replaced all the wires and plugs, and also had the mechanic run the scanner thru. Eventaully i told my mechanic(which is no longer) to not call me until he found the problem. $170 and a compression test later, he found the back drivers cylinder was at 60 psi and was 99% sure it was the ehxuast valve sticking.( he shot oil in and no leaking) Ended up being the intake valve, cracked in two spots and seating is a LITTLE off!

So about 2 months ago I really started looking hard for heads. The first week I really started to dig into ebay and other parts sites, I found a set of original gt-40 heads out of a 1993 mustang on craigslist. I actually have met the guy before. That night i met him and did not hesitate to give him a down payment until I went to the bank for the rest of the payment. The heads were very clean, he kept them in plastic totes with bubble wrap very well oiled, and there was very little,if any, sludge on them. He said the guy with the mustang probably went with different heads because the GT-40 heads came in TRICK FLOW bags. $350 for the heads, valve covers and a camshaft. within that week i brought them down to a local machine shop figuring a leak test and cleanup would only take a few hours...WRONG. 8 WEEKS. The first 2 weeks I wasnt concerned because I wasnt ready to swap them in, but after the 3rd I called him every friday and he gave me the "oh yea, they'll be done next friday." 6th week I called and was going to tell him I would be down to pick them up, but he said they were cleaned up. Another week and no answer. next friday I called and reamed him a little and he got on them. I had him put in exhaust valved because a few were pitted, but the rest was in excellent shape.

Anyways heres what i did

Pop the Intertia switch and relieve the fuel pressure. Theres a Shrader vavle on the drivers fuel rail if you need to double check. The pressure will be releived, but there will still be fuel in the rail.

Drain the coolant. I don't know if this was a big NO NO or was worth the effort, but the T that goes onto the EGR valve down to the heater hoses, take it off the EGR and I shot a a low pressure air to try to blow out some of the coolant in the block. BUT if you can break loose the block drainage bolt on the drivers side, that would be the best bet. If not, be ready with a fresh oil change right after everythings put together.

HEADERS/Manifolds. I have a set of long tube headers which i was able to take off completely and out of the way. The less junk in the engine compartment, the better for me.

Spark Plugs. If you plan on throwing the old heads, it up to you to take the old plugs out. I did on mine because I began to sit on the core and put my feet on the frame.

Intake duct. I have a custom intake to it took a matter of seconds to take mine off. Stocks ones are the same....

upper radiator hose, heater hose...all the hoses that connect to the lower intake and thermostat housing. take these off before you pull the distributor because you'll probably get some coolant dripping out one of them.

Before I go any further, I would like to mention I marked all my connections, vaccum lines and plug wires with green masking tape. All of my bolts were labeled according to the haynes manual(tightening routine) and put in ziplock bags also labelled. You can do whatever you want, but the green tape helped me find the connectors instead instead of digging thru everything. I also took pictures of the coil and vacuum connections.

A/C Compressor - 4 bolts 1 connector
Power Steering - 3 bolts 1 nut 1 connector
Alternator - 2 bolts, 2 connectors
Smog Pump & tensioner pulley 3 bolts, 1 nut(timing pointer) Hose clamp near the back of the block, passanger side

They all have to come off. I kept the a/c and power steering connected, but just threw it off to the side.

Dipstick - it should pull right out. Take note what manifold or header tube it went thru. It should go in at a slight angle, which will be from the back to the front.

Coil/vacuum lines. Take note on the colors and which connector they came from. This is something what I wrote down


Disconnect the Speed and Criuse control cables

Throttle valve or kickdown cable

I have a aftermarket temp sensor, so I had to disconnect that.

Theres two studs on the lower intake which the wiring harness bracket and coil bracket is bolted to. All of the lower intake is 1/2 heads. take the two nuts off and move that well out of the way. Any other connections in the way take off, label and get it out of the way.

Distrubutor. You can take the wires off competely or just take them off the plugs, but you'll need to pull the distributor. Mark where the rotor is on the housing and make a mark on the housing to the block or intake. Unbolt the tab which holds the distributor in place. (1/2 head") Then simply pull it straight up. You shouldn't have to twist or pull too hard. Make sure the O ring is still on it. You'll be replacing it anyways, but its probably not a good thing to have around the camshaft. plug the hole with a towel or rag.


you can either leave the throttle body on or take it off to clean it. Either way, there is a electrical connector on the bottomside of the throttle body which is held on by two phillip head screws. Mine were on good, so I took the TB off the intake and set it on the fenderwell. Also, mark the two vacuum hoses on the throttle body. On the upper intake, there will be 6 bolts total, 5 being 1/2 heads, and one a #40 TORX. There should be a cover on the front two bolts. Why, I dont know. I broke all them loose and took the back ones off first being they are kind of a pain to reach to, especially when you have to hold the intake up so the threads wouldnt catch. For the torx#40, it is located in the center, underneath the plenum. There is a slot where you can get your driver in instead of going from underneath which I did the first time. In order to get it from the top, you WILL need a 6" 1/4" extension and a 1/4" socket. I punched the torx bit out of its holder and taped it to a 1/4" socket because that was the only way it fit.( see picture with fuel line tools) Once the 6 BOLTS are off, it should pop off easily.

Next is Fuel Lines. Even at 50,000 miles, my fuel lines werent the easiest to get off. I ended up using a screwdriver to carely pry the flage out, but it wasnt the best idea. somewhere along the line, I managed to kink the line right after the feul pressure regualtor. the stores don't carry these and you will only find them at the junkyard or maybe Ford. I had to go to the salvage yard and they pulled a fuel rail off an 87 which was 1 1/2" wider than mine, so that was a waste of 3 days. I first bought the White connectors which work the best. The others that i bought( to the left) work, but you cant grab the connector and twist it off.

Here is a link of another of my posts

if you look close at the picture above, there is a round spring which holds the flange in on the other part of the fuel line. Once you put the tool in, and hear the Clicks, that means you are over the spring. You can take the tool off and visually check and see if the flange is over the spring. If it is, then grap onto the big chrome ring and twist it and pull away. Or push it away with your thumbs.

once those are disconnected, disconnect the fuel injecotr connectors. mark and label as desired. Also the IAC. The two bolts in the back(#7&8 acorrding to haynes manaul) have another bracket for the wiring harness. Also, each bolt with have a ground wire. again, they hare 1/2" heads. You may have to have a open end wrench on the bottom nut while you take the top nut off so you dont twist off the bracket. There should be 12 BOLTS holding on the lower intake. Two of them will be studs which the wiring harness holds onto. Again, loosen according to the haynes manual and label as desiried. You may have to pry a little.

I had a table layed with white paper so i could write on it for all my parts. Even that table, a potable bench for tools and the workbench for new parts was full!

HEADS. Theres a bolt on the back of both heads. I think they are for the SMOG.
Take the valve covers off.
Loosen the rockers so you can take the pushrods out, I used a shoe box and poked them thru accordingly.
While taking the head bolts out according to the hanyes manual, TAKE NOTE the bottom bolts go into the water jacket. coolant WILL come out of them unless you drain the block. I took the back one off first, jacked the truck up and drained it(on both sides) Once they are all out, pry the heads off. They should hold on the two studs on the bottom of the block(sleeves in the bolt holes) make sure the two on each side are still there. An assistant is nice to have at this time.

I used a wire brush on my foredom to take off all the old gasket ect. Scotch brite pad works good too This is the time to check your lifters, pushrods, ect ect.

Heres my heads

I purchased the 1988 302 Felpro Head gasket kit which includes all the gaskets from heads up. This was proably the most stressful part of the repair because the gaskets were identical. i went to every store in town and they all were indentical gaskets. the directions blew under the table so I was a little hesitant to put them on this way

You'll notice the color is up on one and the other is down. With the gaskets this way, FRONT is stamped on both the top and bottom of the gasket. THIS IS THE RIGHT WAY TO PUT THEM ON, after 3 hours I found the directions and it said this is the right way. Make sure the front is facing front and the water ports are on the back of both sides. One colored marking will be facing up, and the other facing down.

I ordered new head bolts. they didnt have any for an 88 f150, but they did for the 92 mustang. they were the same size, only these are the "tighten to toruqe" or whatever.

The two studs on the block will hold the gasket in place and putting the new heads in will be a breeze because of these studs. No moving the the gasket ect. Do Not use any RTV. oil the new head bolts. new head bolts should have sealant on it for the bolts that go into the water jacket. Tightten then tourqe the bolts to specs. Connect the two bolts in the back of the heads

Install the pushrods, tighten rockers. Again, oil the rocker bolts,pushrods and lifters.

Install the valve covers. THE STOCK Valve covers dont not work. They line up, but your pour hole will be in the back of the engine and these is not PCV hole in the passanger

Installing the lower intake. (replace the fuel inejector o rings with new, fresh oil) The felpro gasket kit comes with two front and rear seals. Throw them right over your shoulder. Use a generous amount of RTV. I didnt use enough the first time and had a leak. It sucks having to take it back apart. The second time i did a thick bead on both the block side and intake side, for double assurance. you can use sticking adhesive to help hold the gasket from moving, but the two slots that hold onto the head gasket keeps it pretty well in place. Tourqe to Haynes manaual routine. Connect the back bracket and both ground wires. Check to see if that RTV gushed out on the front and back. Hook up fuel lines. it shoud simple "click" into place

Install upper intake. Again, you can use the sticking adhesive to keep the gasket in place. Toruqe to specs

install distributor. it should fall into place(remember the new o ring)

hook up front assembly, spark plugs, exhaust, vacuum lines, electrical connectors ect.

cross your fingers and hope for the best!

any input, questions?

Hope this helps!
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How's the truck run?
Nice write up. I'm doing the same thing but would add to use engine assembly lube on the camshaft, rockers and ends of the push rods.Other than that you methods is 100% identical to what I'm doing but I opt out and replaced my pushrods for new rods.
How's the truck run?
Right now its at my mechanic getting scanned, TV cable adjusted and overall check everything over.

But from when i have driven it, it was running rich and I babyed it. but it sure did feel nice being able to go in 3rd gear in town without getting bucked out of the seat! It doesnt sound like I have a big exhaust leak either
1993 Mustangs do not come from the factory with GT40 heads. The GT40 heads come in Explorers.
93 cobras did
93 cobras did
1993 Mustangs do not come from the factory with GT40 heads. The GT40 heads come in Explorers.
Explorers came with GT40P heads.
Explorers came with GT40P heads.
Not until 1997. Up until that point, they were indeed GT40, and can be identified by three vertical bars on the ends. Research people, research! :rofl:
My dad is a 5.0 fanatic... I knew the COBRA had the gt40 heads, but I never read anything about these heads coming from a cobra. Either way, nice work and I hope that engine works well for you.
My dad is a 5.0 fanatic... I knew the COBRA had the gt40 heads, but I never read anything about these heads coming from a cobra. Either way, nice work and I hope that engine works well for you.
The Cobra valve covers gave it away to me...

Nice writeup :thumbup


head gaskets

Heads, Valve Job, Gaskets, antifreeze, oil, and other misc. it cost about $1000

Spark Plugs. I originally bought Autolite Platinums because the guy at auto value said they were good. After only a week of use, I ended up replacing them with the cheapo coppers which I HIGHLY suggest doing.

Details .......
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Is there are thread that details all what vehicles had GT40 heads? Also, what is the advantage of GT40 heads? Will mustang upper/lower intake and throttle body work on 1990 302 f150?
From the many GT40/40p threads you can learn what vehicles came factory with theGT40's. I'll say it nice first SEARCH!! I have been searching endlessly and there isn't just 1 there are many.

1995- May of 1997 v8 explorer's = GT40's

May of 1997- end of 5.0 in explorer's =GT40p's
Mustang COBRA unsure of year range = GT40's

Your intake question: Sure it will work, with some modification!!
There are many responses to this same question. BUT there really isn't any advantage to swapping to a standard Stang intake.

That spring for the "inline" fuel line is called a "Garter Spring" which costs about a dollar.....keep an eye on it because it was originally "recalled" by Ford for failing, mine did when I first got my BKO nearly 6 years ago and the line seperates and fuel will piss all over when you go to start it....:cry


Do your GT40 heads have the holes for the cross-over tube on the back for emissions..........?

Did use the Crane roller rockers and how did you adjust them.......?

What exhaust headers did you use......?

Can I use the stock valve covers from my 1986 302 E6 heads or do I need to use the stock GT40 valve covers for hidth.........?

There is a You-Tube video called "GT40p and GT40 Iron Cylinder Heads" but it wasn't well lit so parts of it are hard to see but it does explain everything you need know about the difference between these heads.....just a thought......

Great write up Brother.....:twotu:
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Is there are thread that details all what vehicles had GT40 heads? Also, what is the advantage of GT40 heads? Will mustang upper/lower intake and throttle body work on 1990 302 f150?
NO smog or bypass connections on the back of the heads.

Mustang intake ( lower and upper ) would mount on our engines , but you will need to be creative on the linkage for gas-pedal cable, TV cable and cruise control.

I'll post some comparative views of the GT40 vrs GT40P heads soon, since I have both in my store room.
I'll post some comparative views of the GT40 vrs GT40P heads soon, since I have both in my store room.
Thanks that would be awesome. eBay has tons of GT40 heads for sale. Is the money worth it, or is it better to just port my stock cast heads? I'm paranoid of aluminum anyway from a couple bad experiences with exhaust and spark plugs.
dunno if you noticed but you have a factory roller block, could be a nice up grade in the future if you want a roller cam...
Thanks that would be awesome. eBay has tons of GT40 heads for sale. Is the money worth it, or is it better to just port my stock cast heads? I'm paranoid of aluminum anyway from a couple bad experiences with exhaust and spark plugs.
if you can find a set for under $300, then I think they are worth it. I've sold some on ebay and locally from as low as $180-to-$350.00. Aluminum are not bad for the weight saving, but I know what you mean by bad experience.

I've personally had damages from strip plugs, and other issues from my racing experience and if you overheat them. With aluminums, you have to look at the cost,weight savings and performance gains and then the dollars spent.
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