How much H.P. would a set of headers give me?

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moparguy

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I have a 72 Duster with a 400. Mild build, including: 452 heads shaved .060, Weiland dual plane intake, comp cam 224/230 duration 477/480 lift, 750 cfm holley, and i'm running stock type exhaust maninfolds. How much Horsepower should a gain if put some longtube fenderwell headers? Is it worth it? and how much trouble are they to install?
 
Headers are generally worth 25-50 hp depending on the combination especially if you currently have the so so lo po manifolds and not hp manifolds. Not sure on the install but shop companies i'm sure some are better than others in the fit department.
 
What kind of manifolds are you using that fit in an a-body? Are they the factory a-body HP manifolds.


Chuck
 
They was on the car when I bought it. I almost sure they are not HP manifolds.
 
Fenderwell headers can be tuff to do. Tti's would be an easier fit at a price.
On a mild build, stock engine to stock and bolt on's, a general rule of thumb we used to use was 15%.

This is also due to the old carbs/engines running rich from the factory and the headers would lean out the mix to proper (or close to proper) levels/ratio's.

A typical 340 @ 275 HP would generate 300+ HP everytime, tuning the carb just right was allways worth another 10 peak HP.
 
That's a significant gain. I know you have to cut big holes in your inner fenders, other than that, what else is involved that makes them tuff to do?
 
Can you get a casting numbers off the manifolds? I was thinking of doing a stock BB conversion on my wife's Scamp and want it all iron.


Chuck
 
There are decent underchasis headers for a B-motor in an early A body. So unless you absolutely have your heart set on cutting up your inner fenders, I would avoid fenderwell headers. TTI's arent cheap, but neither are Hooker Super Comps. And cheap headers generally suck.

Do you drive this car on the street?
 
Will take a look later for the casting number. Although, I will say my motor isn't on stock mounts.. It has modified schumacher mounts. Clearance issues.
 
OK, thanks.

Now back to your question; Being you say it has modified mounts and I assume that they were modified to move the motor, you might want to reconsider the header thing. There is a very good chance they won't fit because of your motor location.


Chuck
 
Yes, this car is strictly a street car. I used to have a 69 cuda with a 440, I did install schumacher headers on it, but they are pricey and i had to raise the motor to install, as it had power steering. I can't afford that kind of money and i don't want to much hassle. I was thinking i could find a used set of fenderwell headers on ebay and other than cutting the holes wouldn't be to much trouble.
 
340mopar said:
OK, thanks.

Now back to your question; Being you say it has modified mounts and I assume that they were modified to move the motor, you might want to reconsider the header thing. There is a very good chance they won't fit because of your motor location.


Chuck
Click to expand...


Are fenderwell headers that close of a fit. I believe the motor was lowered roughly 1/4" on passenger side and shimmed up an 1/8" on drivers side. This is from the schumacher location. Wouldn't i have a little more room as it is a B motor not a RB?
 
If you're running the Schmacher mounts then the Schmacher headers won't be a problem. I didn't have to lift my engine when I installed them on my 71 383 demon with power steering. The TTI's also won't be a "big" problem and every once in a while both headers appear on ebay.

Terry
 
I had a set of fenderwell headers on a 68 ,383 Dart and there were tire clearance problems in turning with a 14" tire. Inside the engine compartment was not that bad.
 
Long tube headers are worth a noticeable amount of horsepower, and a LOT of low end (if the carb is right). Even thru stock exhaust. More than the difference between pulling the torker or street dominator manifold off and going to a dual plane. In my book, they're a 'must have' for performance. And some PITA (depending on brand).

If you have a low-deck 361-400, you can use low-po "logs" like were on a C-body.

They can get a little close to the bottom of the steering column; I had to grind about 1/4" off the flange on my Valiant.

I'm negotiating to get the old girl back... and I won't be fooling around with any iron logs this time. But that's just my personal preference.

-bill
 
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