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Got my GT40P up and running in my 66

62K views 172 replies 28 participants last post by  dbfarr 
#1 · (Edited)
I waited until I had it up and running with the bugs worked out before posting so if anyone is planning on doing it, they'll have all my info ready to go and not waiting on me. Sorry for the poor cell phone quality, it's mostly to show it actually running. It's taken me a while mostly because I'm not home during the week. it's been a little here and there. It runs really well. The specs are a stock Mustang 91 5.0 used roller cam, used Weiand Stealth, a used yard shed Edelbrock off ebay, off the shelf long tube headers and used Ford Cobra 1.72 roller rockers and a points distributor for now. Yes, off the shelf regular, unmodified long tube headers. I'm not going to post to much more tonight. I just wanted to kick it off. I'll be posting a fair amount of info and photos. While I realize this isn't the first one done, just the most current there still is some new info as no two swaps are the same. Feel free to ask any questions.



Here's what I started with. A 97 Mountainer GT40P with less the 40K miles.

 
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#90 ·
obviously the ceramic is the best choice as it’ll last longer, keep heat down and improve flow by keeping the heat contained. But that price thing, I agree and I just used a couple light coats of VHT brand paint. It’s held up a lot better then I thought. If you’re going to use ceramic I would advise getting uncoated and after you’ve fit the headers get them ceramic coated. With my MAC headers it whike not designed for the P head they will work, a little tight but again will work. As such I did not have to make any “adjustments” with a BFH to clear any of the plugs. I did have to make 3 “adjustments”. 2 of them were for tubes that were touching or barely touching the frame rails. The other “adjustment” was for the Z bar shaft for the horizontal tube from frame to motor. I have great access to the Z bar and linkage as well as the starter. The MAC headers will also clear a PS ram without the need for the typical drop bracket. Over all I would highly recommend MAC headers even if it’s not a GT40P.
 
#97 ·
Ford used 2 different diameter of manual flywheels and flexplates. The smaller diameter used 157 tooth and the larger used 164 tooth. The early small diameter 160 tooth is the same diameter as the 157 tooth flexplate and uses the same starter. Ford revised the 160 tooth to 157 tooth to make the ring gear more robust. Think of a 160 tooth as a 157 tooth from a function standpoint.

This is the flexplate you’ll need to put a GT40P or any other 1982 and later 50 oz motor into a early Mustang with a C4

https://www.ebay.com/itm/Scat-SFI-F...946985&hash=item58abe825f2:g:XlYAAOSwVDZaBcRS
 
#96 ·
If your engine is a later 5.0 then it will have 164 tooth "big" flexplate because it had a 4R70W behind it. There exist "big bellhousing" C4's from trucks and like 1982 Mustangs that used the larger flexplates but they are kind of hard to find and word is that they don't fit into a vintage Mustang tunnel that well. If you had one of those bellhousings then you could keep using the 5.0 flexplate you have.

Best to just buy a 157 tooth flexplate to fit your C4's bellhousing with the correct 50 ounce imbalance to fit your 5.0.
 
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#100 ·
Rose, the Exploder cam is very mild and doesn't have much lift. The heads you have are awesome for a factory set, but with stock valvesprings, they really won't take the extra RPMs or lift. To put in even a 5.0 HO cam, you'd really want to replace them, or all you'll get is valve float, and possibly end up with piston-to-valve interference. The stock Explorer motor poops out around 4500 or so.

The E cam would not be a very good choice if you have stock 2.79 rear gears and a stock converter, either. That setup would be pretty weaksauce out on the street. The cam you choose needs to take the rest of your engine into consideration. Because you're running an automatic with (presumably?) highway gears, you'll want a 'mild' cam that can produce torque from very low RPMs. Your 4100 is an awesome little street carb.

You didn't mention which intake you're running, but hopefully it's a good dual plane, capable of producing good torque from at least 2000 to 5500 or so. Think Weiand Stealth, or even possibly the Edelbrock Performer RPM Air Gap (which is a little better suited to higher-rpm fun).

If you decide to upgrade your rear gears to something better suited to off-the-line acceleration, then having a cam with more overlap begins to make sense (better suited to high-rpm torque production = horsepower). You'd also want a high-stall torque converter; maybe something around 2400 RPMs. With a hot cam, and the ability for your car to hit higher RPMs before starting to spin the tires, you might even want a single-plane intake to maximize high RPM performance, albeit at the expense of low-to-midrange power. At that point, you might also want a bigger carb on there - something in the 600-650 CFM range, probably.

You'll likely wind up in the teens for gas mileage, but you could sure get up and go.

A lot of people tend to replace just one or two parts with something 'high performance' and then wonder why their car runs terrible. Your car's drivetrain has a lot of parts, and all of them need to work together with each other. Changing just one aspect may cause enough trouble for the rest that it all works worse than stock. It was smart of you to ask what would happen!

Best wishes.
 
#102 ·
Oops, just went back and read your first post! Great choice on manifold. The rockers you're running put more stress on the valvetrain anyway, so I'm thinking those springs are living life on the edge as it is. Exploder springs are notoriously wussy.

Because you've got more duration and lift from the 1.72's, you're probably getting a few hundred extra RPMs out of your engine, but I bet it still falls flat on its face at the end of revs.

Even a stock 5.0 HO cam (not Explorer!) or mild performance cam would probably really wake your engine up, once you have valvesprings that will keep you from tossing the valves at 5500. Looks like you've picked your parts combo well!

As a side benefit, even if your stock C4 and 2.79's are not super for drag racing, you still have a passing gear at 70 mph out on the highway, and from a rolling start, your car probably doesn't have to back down to anyone. The tall gears out back also mean your driveshaft is not spinning that fast, so you have less vibration when you're out on the open road.
 
#103 ·
I did put a 91 5.0 Mustang cam in. I took the roller rockers out last year and put the factory stamped rockers back in. The roller rockers were very noisy. To be honest it seems to run every bit as well , maybe better! My motor pulls very easily up to 5500, I don’t go much past that deliberately. The 5.0 cam, Stealth intake are very effective on the GT40P. The seat part is how little money I have tied up in the motor. My last comment, the GT40P head only needs 28-30* total mechanical timing due to their efficient combustion chamber. No matter how hard I lug it with 87 on the 9.5:1 compression I can’t get it to rattle.

That’s exactly why I have the 2.79’s. It’s a light car, motor has a lot of low end and the 2.78 first gear works well. Yes, great passing gear at 70! Talk enough for comfortable cruising but low enough that you’re not constantly down shifting on small hills.
 
#104 · (Edited)
You probably know this, but I just want to mention, 5.0 is not the same as 5.0 HO. A lot of these motors went in Crown Vics, Rangers, and the like but they didn't get the high-output treatment. No forged pistons (or later Hyper), no fun little cam. And even if you DO have an HO cam in it, you're probably still going to be limited by valve float. I am not surprised if it runs better with the 1.6 rockers, with the Explorer springs in it. Oddly enough, the Explorer motors have "HO" badging, but they really aren't the same as the other HO or 'lo-po' 5.0 motors; they got great heads, intake, and a really low-RPM torque producer cam without much lift. Okay for a truck, I guess.

If it's rolling up to 5500 easy, then it's probably HO. The stock 5.0 cams do poop out not far north of 4500, even with GT40P heads.

Sounds like your build is actually very similar to mine! =) Hope you are having a blast with it. And honestly, if you're going to upgrade the cam, if you can find an E for dirt cheap, it might be fun! The old E-cam has a nice broad torque curve, and just a little more lift than the HO. But to make it work, I really think you'd need a higher-stall converter, or it's going to bog pretty bad. (Not to mention new valvesprings!)
 
#105 ·
Yep, I’m aware of the different designations. The cam I’m using is out of a 91 Mustang. A 80’s Mustang cam would have been better. I actually was going to put a E cam in. Someone on another forum gave me one for the cost of shipping, $14. Unfortunately at some point packed nice and safe in the cam tube in my garage it got wet and no longer useable. In preparation for the E cam I did install .540” springs from Alex’s parts. Right now I’m pretty happy with the current configuration. I was talking with a guy on FB with GT40P heads on his 90’s 5.0 Mustang, T5, 3.27 gears said he was running low 13’s with the stock Mustang cam
 
#111 ·
Ford cams are not as easy as A B C. More like B E F X Z?
 
#125 ·
0.480 lift on the "B" cam? Best to leave Moses out of this one. A 5/16 race cam at best!:grin2: Now the "X" cam at 0.542 lift and a much broader rpm range sounds interesting but it's all just voodoo to me.
 
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#128 ·
Everything is a trade off.
Long duration cams with a lot of overlap will bleed off compression. So your engine with 9:1 static compression may only have 8:1 dynamic transmission. Not so good for making power.
Best to start with 10:1 static compression. (Of course this is not a hard rule and depends on a variety of factors)

On the other hand, long duration provides more time to fill the cylinders with air. This promotes “stacking” but that only occurs at higher RPMs. Thus, long duration “race” cams idle poorly and don’t have much power at low rpm.
This is why camshaft manufacturers specify rpm ranges, compression ratios, etc.

It’s not voodoo when you build an engine for a specific application with parts designed to work together.
If unsure, stick to a conservative cam profile. High lift cams require valve springs that can handle the lift. Otherwise you will run into valve float.

Modern engines use variable valve timing or variable cam timing to adapt somewhat aggressive camshafts to a variety of changing conditions. Now, that’s voodoo.
 
#131 ·
Nearly finished with engine bay prep so stripping the long block will be coming soon. I see several vendors selling timing covers for reverse rotation WP's along with the boss for the mechanical fuel pump. This will allow me to run the serpentine setup. Are there any interference problems with this setup and a carb? Do the companies selling aftermarket A/C systems sell the units with the serpentine compressor pulley? I'm leaning toward this setup mainly to afford myself the reverse-flo water pump and cross-flo radiator. As a refresher, it's a '66 into which I'm putting a 2000 GT40P engine in front of a C4. Still undecided on cam, radiator, headers, distributor and rear gears.
 
#132 ·
As long as the water pump physically bolts on the timing chain cover no matter rotation, you’re good to go. You could bolt on a 80’s Mustang 5.0 water pump onto a 65 cover and work. The two problems how ever would be the timing pointer that’s cast in the cover will be blocked from view with the lower hose. Another possible issue is the dip stick. The cover mounted dip stick may be in the way of the alternator or tensioner, that’s why the 5.0 has the dip stick in the left side of the block.

As long as the cover uses a bolt on timing mark you’re good to go with the reverse water pump.
 
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