67 GTX 440 Rebuild, 915 Head Upgrades

Fullthrottle303

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Wanted to know what you guys thought were worthwhile upgrades for my 440. I drive the car everyday, have a rear main leak and am going to paint the motor. I figure it's probably a good time to rebuild as it will be out of the car. Definitely changing the camshaft to wake it up and get a more respectable sound. Problem is I don't really want to change the 915 heads because I want to keep the car period correct. Is it worth a stroking or putting headers on if leaving these heads? What is the potential of these heads and who knows Mopars and 915 heads well enough to make it worthwhile to port them? I know it's cost prohibitive, but I really love this car and I think keeping it more factory looking is more important than the bang for the buck I could get with aluminum heads. Open to running headers if it's worth it while keeping the heads. I run a Holley Sniper, Torqueflite, 3.23 Gears, and will probably look for a torque converter with a 2600-2800rpm stall. I drive 15-20 miles per day in town and hwy on weekdays, around 100 hwy miles on the weekends when the weather is nice. Would love to change gears, but I'm already running 3200rpm at 70mph. Thank you for your time.

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Jerry Hall

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I'm to old school to tell you what to do with today's crap gas. As my 440 GTX'S aren't driven as much as your car, I find that getting the octane up in the high 90's makes my cars run more like they did in the day. If it were mine as I intend to continue mixing my gas for 96-98 octane, I would install hardened seats and 2.14/1.81 valves and pocket port the heads. I would also keep the compression ratio in the high 9's or even at 10. JMO
 

R413

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You talk of keeping the car period correct Then you have EFI and want headers, aluminum heads, and a stroker.

these things don’t add up
 

Cranky

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A agree with Jerry....but if you're going to keep your front end that low, headers are gonna drag on lots of stuff. The 915 heads are pretty decent ones and lots of people want them but there are aftermarket heads out there that still look like factory heads if you don't really want to spend the money on mods on an original set....
 

Fullthrottle303

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R413- I said I was trying to avoid aluminum heads, headers are period correct, and you can't see the fuel injection or a stroker crank. Or at least I can't. I'd like to avoid headers just because of the possible leaks, but if they are more of a bottle neck than the heads, I would probably run em.
Cranky- Good point that I probably would have to raise the front end. I installed larger diameter torsion bars and it rides pretty well where it is, and I like the look with the roof parallel to the ground so I'd like to keep it there.
Jerry Hall- I guess my question was more along the lines of what is the limiting factor, heads or stock exhaust manifolds, and if it's the heads does anyone know a reputable shop to modify them. If I install larger valves and pocket port, would the stock manifolds likely be insufficient or still adequate. I'm sure someone who's spent some time modifying this particular combo knows the answer. Just trying to do the right things without wasting money, I have enough projects to get rid of all my cash.
 

Cranky

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R413- I said I was trying to avoid aluminum heads, headers are period correct, and you can't see the fuel injection or a stroker crank. Or at least I can't. I'd like to avoid headers just because of the possible leaks, but if they are more of a bottle neck than the heads, I would probably run em.
Cranky- Good point that I probably would have to raise the front end. I installed larger diameter torsion bars and it rides pretty well where it is, and I like the look with the roof parallel to the ground so I'd like to keep it there.
Jerry Hall- I guess my question was more along the lines of what is the limiting factor, heads or stock exhaust manifolds, and if it's the heads does anyone know a reputable shop to modify them. If I install larger valves and pocket port, would the stock manifolds likely be insufficient or still adequate. I'm sure someone who's spent some time modifying this particular combo knows the answer. Just trying to do the right things without wasting money, I have enough projects to get rid of all my cash.
EVERY time I installed headers on a stock engine with a better intake manifold and bigger carb, I actually felt the difference and on the several that went to the track, the ET times were better too.
 

Fullthrottle303

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Thank you Cranky, that's usefull info that tells us the exhaust manifolds are definitely the most restrictive part. So if I can find someone that can tell me the max hp the 915 heads can support, stock vs modified then I'm on my way to building an efficient combo.
 

67charger383

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If you really are driving it every day, keep it relatively stock.
If you don't want a race car, don't build a race car.
 

Runcharger

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I would pocket port the heads for sure. I would also build for quench when you order your pistons to take advantage of your excellent iron heads. You'll get more gain from properly prepped heads than you will from headers IMO. And yes if you install headers they're going to drag on speed bumps and such with your frontend that low.
I wouldn't build a stroker for a car I drove everyday just because it will use more fuel than a stock stroke 440 and a stock 440 will do everything you need and more if correctly built.
PRHeads is a member here and his headwork is highly regarded, I think sending them to him would be an excellent investment.
I built this GTX years ago with ported 915's, 3.23 gear and a solid lifter camshaft. It was very tractable and ran in the 12's fairly easily. The 67's weigh about 3700 lbs so it's not that hard to make them run hard.

67gtx.jpg
 
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Cranky

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I would pocket port the heads for sure. I would also build for quench when you order your pistons to take advantage of your excellent iron heads. You'll get more gain from properly prepped heads than you will from headers IMO. And yes if you install headers they're going to drag on speed bumps and such with your frontend that low.
I wouldn't build a stroker for a car I drove everyday just because it will use more fuel than a stock stroke 440 and a stock 440 will do everything you need and more if correctly built.
PRHeads is a member here and his headwork is highly regarded, I think sending them to him would be an excellent investment.
I built this GTX years ago with ported 915's, 3.23 gear and a solid lifter camshaft. It was very tractable and ran in the 12's fairly easily. The 67's weigh about 3700 lbs so it's not that hard to make them run hard.

View attachment 1174656
Down side to the GTX.....weight!
 

Jerry Hall

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Down side to the GTX.....weight!
Weight is not the real down side of the 66-67 cars, it's the amount of tire you can get under it without modifications. Most other big block B bodies are not that much different in weight.
 

Cranky

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Weight is not the real down side of the 66-67 cars, it's the amount of tire you can get under it without modifications. Most other big block B bodies are not that much different in weight.
Well, 3700 isn't exactly light and combine that with a small wheel house, yup, that's a double whammy. My 66 Belvedere 2dr sedan was 3370 with a /6, auto and factory AC but got it down to 2950 without much of a hassle. Just doing that alone improved 1/4 mile times....but even after doing that, it still wasn't too impressive but shaving off almost 4 seconds isn't anything to sneeze at :D I did some other mods but to accomplish that but they weren't anything to write home about. Other than the weight, the car was just that bad. In the end, took off 5 1/2 seconds before tearing it apart for a V8 transplant.
 

1967coronet

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Nice car !
Just thought I would toss in( triY) headers.
Best of both worlds if you get a decent set.
Good flow and ground clearance.
 

BSB67

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You talk of keeping the car period correct Then you have EFI and want headers, aluminum heads, and a stroker.

these things don’t add up

I'm with you. I cannot see cast iron head verses aluminum Stealths under the paint just like I cannot see a stroker crank.

Add that we don't know what he wants in idle and driving characteristics, current power level, power level objective, and budget, there is no meaningful advice that can be given. Power/drivability/reliability/cost is a balancing act, and some are inversely related.

The real bottleneck to power is the factory intake manifold. It's hard to make more than 350 hp with the factory intake. Will that be used or replaced with aftermarket aluminum? Are all aluminum intakes period correct? If not, which ones?

The exhaust manifolds and 915 heads can support 600 hp. You are probably at 280 hp now. The exhaust manifolds will likely not keep you from your performance goal, but the headers will just make it a little easier. But there are downsides to headers - again, balancing act.
 
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Fullthrottle303

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I'm with you. I cannot see cast iron head verses aluminum Stealths under the paint just like I cannot see a stroker crank.

Add that we don't know what he wants in idle and driving characteristics, current power level, power level objective, and budget, there is no meaningful advice that can be given. Power/drivability/reliability/cost is a balancing act, and some are inversely related.

The real bottleneck to power is the factory intake manifold. It's hard to make more than 350 hp with the factory intake. Will that be used or replaced with aftermarket aluminum? Are all aluminum intakes period correct? If not, which ones?

The exhaust manifolds and 915 heads can support 600 hp. You are probably at 280 hp now. The exhaust manifolds will likely not keep you from your performance goal, but the headers will just make it a little easier. But there are downsides to headers - again, balancing act.
Motor is rated at 375hp from the factory with that manifold, was that an exaggeration? You provided some pretty good information, but apparently felt the need to weave in some garbage. If Stealth heads painted are indistinguishable from 915 heads, that is pretty usefull info I would have been appreciative of. Not sure what you are with him on, besides saying I said I want headers and aluminum heads, and that a larger stroke would make the car look less period correct. We are all busy so skimming what I wrote is no big deal, just not sure why you would take the time to respond if that's the case.
 

Jeff_383

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I'm with you. I cannot see cast iron head verses aluminum Stealths under the paint just like I cannot see a stroker crank.

Add that we don't know what he wants in idle and driving characteristics, current power level, power level objective, and budget, there is no meaningful advice that can be given. Power/drivability/reliability/cost is a balancing act, and some are inversely related.

The real bottleneck to power is the factory intake manifold. It's hard to make more than 350 hp with the factory intake. Will that be used or replaced with aftermarket aluminum? Are all aluminum intakes period correct? If not, which ones?

The exhaust manifolds and 915 heads can support 600 hp. You are probably at 280 hp now. The exhaust manifolds will likely not keep you from your performance goal, but the headers will just make it a little easier. But there are downsides to headers - again, balancing act.


None of that was garbage, he knows what he's talking about. And he hit all the important points of creating an engine to do whatever it is your goal may be.
 
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