HP Manifolds or Headers

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Rbob

Rbob

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Putting a 440 in a 67 f/b Barracuda and I am struggling with the use of headers or HP manifolds. How much power can one lose by using the HP manifolds?

I know the headers are expensive and have a fit issue just not convinced it is worth it.

Your thoughts please.
 
Combo dependent headers will add an easy 30 HP on a bone stock Lo-Po smog 440.
If you have built the engine up, or if it's a early 400 that has power, like a Magnum engine, you could see an easy 50 HP gain with headers. Torque impoves as much as well.

HIGH performance engines will see more. It's very combo dependent, but I would make the jump to headers useage.
 
The factory manifolds on a 69 440 Dart were so restrictive that a 340 car would take it. Classic case of constipation compared to B-Body manifolds, especially on the left bank.
 
Factory b-body HP manifolds work well enough on a mild engine that headers really aren't necessary. They have their own issues, but I will take manifolds every time. Yes, you lose some horsepower, but less on a mild engine.
 
30-50 horse ?
Dam those bb manifolds must be really restrictive. On a small block test (Mopar Muscle) TTi's only improved a 360 motor by 12 hp,over the 340 HiPo manifolds.
 
I've built several stroker motors over the years that use manifolds. My '65 B body car runs manifolds and it lays down 475 to 500 rwhp. So that is basically the same power as a Viper. That is enough power to put a car deep into the 11's if you can hook it up. If I put headers on it then I'd have to put a rollbar in the car so manifolds work just fine for me. There are some guys into the 10's with cast iron manifolds so for a street car I wouldn't worry too much.

If you do use manifolds then you just have to be really careful about the camshaft choice. I've done a fair amount of camshaft testing on the dyno with manifolds and it is a tricky issue. Too much overlap and the car slows way down. Not enough and the car is great off the line but then lays down on the top end.
 
Johnny Dart said:
30-50 horse ?
Dam those bb manifolds must be really restrictive. On a small block test (Mopar Muscle) TTi's only improved a 360 motor by 12 hp,over the 340 HiPo manifolds.
Click to expand...

That was on a EXTREMELY mild combo.

AndyF said:
I've built several stroker motors over the years that use manifolds. My '65 B body car runs manifolds and it lays down 475 to 500 rwhp. So that is basically the same power as a Viper. That is enough power to put a car deep into the 11's if you can hook it up. If I put headers on it then I'd have to put a rollbar in the car so manifolds work just fine for me. There are some guys into the 10's with cast iron manifolds so for a street car I wouldn't worry too much.

If you do use manifolds then you just have to be really careful about the camshaft choice. I've done a fair amount of camshaft testing on the dyno with manifolds and it is a tricky issue. Too much overlap and the car slows way down. Not enough and the car is great off the line but then lays down on the top end.
Click to expand...

Excellent mention, a good point in this would be the cars that compte in the F.A.S.T. racing class. Pay heed to the camshaft!
 
Johnny Dart said:
30-50 horse ?
Dam those bb manifolds must be really restrictive. On a small block test (Mopar Muscle) TTi's only improved a 360 motor by 12 hp,over the 340 HiPo manifolds.
Click to expand...

He's talking about lo po logs , not the HP manifolds , but there is a gain with headers over the HP's also ... obviously .
 
Yes there is a gain but a big block with HP manifolds if easily capable of making enough power to get tossed off the track so what is the point? For racing headers are the way to go. For a street car I don't see much reason to run them. An A body car stock brakes and suspension but equipped with Viper equivalent power is dangerous as is, no reason to make it extremely dangerous.
 
Andy, that's why I recommend upgraded brakes and suspension regardless of the powerplant or power. I know what the 10" drums are like on my GTS (I have resisted swapping to discs on such a rare car, but it will get them next time it is road worthy) vs. the stock late a-body discs on my son's Dart. I would have those brakes on his car even if we were still running a 273 two barrel.

Same with making the car handle. For what the suspension package cost I have no idea why they all didn't come with it (something like $13 on a 66 Barracuda).

I think a slant six car is dangerous without these upgrades.
 
How about extrude-honed hi-po manifolds w/a thermal barrier coating, a mandrel-bend exhaust (properly size, yes you can go too large on a V-8 just like a n/a Honda with a header and 2 1/2" exhaust), and an X-style cross over. Probably not legal in F.A.S.T competition, but would work excellent on a street/strip combo- efficient flow and low maintenance. What do you think, Andy, is that a good train of thought?
 
I don't think you can go too big on the exhaust. Headers, yes, but once you are past the collector, small pipes just add backpressure. People that say an exhaust system needs backpressure don't have a clue what's going on.
 
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