exhaust manifolds

[70 Fish]

I have a 383 HP engine in a 70 Barracuda. I currently have headers on. I am thinking of putting on stock manifolds to reduce under hood heat. How much more horsepower is gained by headers? I've been told 25-30hp.

Also, if I go to stock manifolds, is there a stock manifold OR High performance manifolds available for this engine? If so, what would I gain by picking one over the other.

[ehostler]

They had both the standard manifold and the HP manifold. The HP will give you about an extra 5 HP.

If you are only doing this for under hood temps, why don't you use header wrap? That will drop the under hood temps to the same or better than manifolds.

[rr69half6bbl]

You will get around 20 horse from a good set of headers, but if you plan on driving the cuda, I`d put the stock hi-flows on it. Ever change a heat soaked starter w/ headers on an e-body? It SUCKS.
To me the 20 horses aint worth the headaches of that and blown collectors, Year one is repoping the hi-Flow maniflods for like 250.00 a set, and from what ive heard they are nice.
If your 383 is mostly stock and is a street car the headers arent gonna give you that much anyway. If it is built, then i would get a set of the TTI. headers, they bolt in and give you more starter clearence, But they arent cheap.

[70 Fish]

The car is mostly stock and its a driver. How much horsepower gain are these Year1 High flow manifolds, compared to stock manifolds?? Are there any test results I can read up on?

[Shaun]

Originally Posted by 70 Fish

The car is mostly stock and its a driver. How much horsepower gain are these Year1 High flow manifolds, compared to stock manifolds?? Are there any test results I can read up on?

There is a big misconception about headers that I find and hear all over-they don't help that much.What are we talking about? Are you running a 4 bbl carb? Do you have a cam with more duration than stock? If so,then you need more exhaust flow-why?,because the more air/fuel that you are trying to push in,will only benefit from an equally good exhaust. Header wrap will solve your starter,underhood heat problems and will keep your exhaust gases hotter(keep the heat in)meaning they will be smaller and flow faster and they will keep the air being sucked into your carb cooler!! Why isn't everybody running the wrap!!! They don't care. They don't like taking off the driver's side header to change the starter and they don't(or can't afford) the copper collector gaskets. Add some wrap and you won't be changing your starter anytime soon.

[dwc43]

I agree with Shaun. Get some header wrap cause headers give you more than a 20 hp gain, but it depends on the engine combo. You start adding restrictions to the exhuast and it will limit your top end severly. A good header wrap will reduce temps a lot. I've actually touched hot headers that are wrapped while working on our race cars before and not even notice it untill it starts heating up. Before if you did that it was instant 2nd degree burn or worse since headers can get to 1500*. And manifolds are not that much cooler.

[MrChemist]

Depending on your plans for your motor in the future, Manifolds could really hold your car back. Take a look at this link for a stroker small block dyno example.
http://www.hughesengines.com/general...icleID=1000028

[jelsr]

Wonder what the price for the 596's w/stage 2 porting that flow 696 CFM @ .600 is.

[70 Fish]

Thanks for everyones' input. Really appreciate it.

[pishta]

These are the ones you want. Simple, elegant and dont leak...(pic stolen from the net)

[darkside]

I have a set of mint 440hp manifolds for sale $200 shipped!Can send pics

[rumblefish360]

Originally Posted by MrChemist

Depending on your plans for your motor in the future, Manifolds could really hold your car back. Take a look at this link for a stroker small block dyno example.
http://www.hughesengines.com/general...icleID=1000028

Mr.C, excellent link to a real good read and demo on the power of headers.
A stock engine will see a lot less and the power added may not be worth the head ache or money spent. Mild engines sometimes will see a whopping 10 HP gain and not much more. (Small block)

[70Ted]

FAST race cars are running low 11s using HP exhaust manifolds.

[pishta]

That is an amazing statement as most FAST cars are almost numbers matching restorations and there are so many stipulations on what can be run in those cars is a great testimony to the abilityof Magnum/HP logs! I may go back to them if I can ind a nice set. They were so much easier to install.

[rumblefish360]

But what those FAST cars could do with headers ,slicks and Cal-Tracs!!!!
Remember the fastest FAST cars are strokers and have lots of hidden tricks to there cars.

[ehostler]

I would be willing to say that the fastest of them have extrude honed manifolds. It isn't cheap and they only gain about 5hp.

[George G. Leverette]

Headers could reduce HP on street driven cars running 93 octane fuel. Headers could gain about 10-15 HP over stock log type manifolds running 105 octane fuel with a 10.5-1 compression ratio because it would lean out the combustion and produce better fuel efficiency. I doubt a set of cheapo headers would produce any HP gain over a set of Magnum manifolds. Headers with ceramic coating and thermal barriers still produce more heat in the engine compartment than cast manifolds, this heat production will negate any HP gains if hot under hood air is introduced into the carb. Thermal wrap is not recommended by some header manufacturers, the moisture build up caused by the thermal exchanges causes rust and premature exhaust pipe failures, besides its tacky looking. Any true dual exhaust system is an improvement over the factory single 2" pipe.

[pishta]

Originally Posted by George G. Leverette

Headers could reduce HP on street driven cars running 93 octane fuel. Headers could gain about 10-15 HP over stock log type manifolds running 105 octane fuel with a 10.5-1 compression ratio because it would lean out the combustion and produce better fuel efficiency. I doubt a set of cheapo headers would produce any HP gain over a set of Magnum manifolds. Headers with ceramic coating and thermal barriers still produce more heat in the engine compartment than cast manifolds, this heat production will negate any HP gains if hot under hood air is introduced into the carb. Thermal wrap is not recommended by some header manufacturers, the moisture build up caused by the thermal exchanges causes rust and premature exhaust pipe failures, besides its tacky looking. Any true dual exhaust system is an improvement over the factory single 2" pipe.

I dunno, mine looked pretty cool with the wrap, like a mummy! And it really deadend the tinny sound of my headers, it was actually quieter with the wrap and much cooler. I didnt run mine daily to work or anything like that so I was not concerned with rust or superheating the pipes.

[rumblefish360]

Thats one thing I did like about the wrapping of headers. Looks cool as well.
Headers almost allways show a gain over the stock manifolds. Theres few exceptions I could think off.
A old test I threw out just the other day had MoPar Muscle (I think it was) doing a header comparo on a 300 hp 360 create engine. The OE log exhaust manifolds were only down something like 10 HP over the run of the mill header. TTI's in this application made a big whoppin 15 or 20 HP over the manifolds.
Clearly not the best arena for this header.
Pump up the power by 100+ HP and there will be a big difference!

[dkn1997]

go check out moparts and look for member andy f. he has a low deck stroker, maybe a 452? runs ported eddies with stock manifolds, not extrude honed, just port matched and he makes in the neighborhood of 500 hp on the dyno.

food for thought.

I ditched headers for economic reasons. I ran cheapie hedmans and when they became too much of a pain to live with, I only saw two options: big bucks tti's, or cheap HP manifolds. I have about 300 bucks into my HP manifolds, and that includes buying them, blasting them, coating them with eastwood stuf and a trip to the man to redo the exhaust. my ass dyno cannot really tell the difference. I could have gotten a slightly better set of headers for that much, but i did not see the point. sounded meaner too, no tinny tink tink tink after that.

as far as the wrap, I just don't like the way it looks. but that might be a good option for some.

stock displacement 440, 346 heads with some cleanup of short turns and the larger valves, 10:1, peformer rpm, 750 mighty demon.