Headers vs 340 manifolds

-
The 9hp is on this dyno comparison doesn't mean the same for the OP's engine, depends on cam, overlap needs long tube headers with the right collectors to function properly, both of the dyno's I shown where stock 360/5.9l cam minimum overlap could say probably minimum power gain from headers.
 
273 said:
Here's mods to a mild 360 manifold's vs headers starts at 5:15

Click to expand...



those look like truck manifolds.. i'd like to see actual 68-71 340 manifolds..

i think it really depends on your combo and intended use, i will say 340 manifolds are getting harder and way more expensive to buy. sure you can find a deal sometimes and get into them on the cheaper side but more and more they are getting harder to find and aren't too much cheaper then a nice header.
 
abodyjoe said:
those look like truck manifolds.. i'd like to see actual 68-71 340 manifolds..

i think it really depends on your combo and intended use, i will say 340 manifolds are getting harder and way more expensive to buy. sure you can find a deal sometimes and get into them on the cheaper side but more and more they are getting harder to find and aren't too much cheaper then a nice header.
Click to expand...
If you look at this dyno shootout a 340 manifold was worth 1hp over 360 and 4hp over 318 manifolds at 300 hp range.

Installing Exhaust Headers Into 300hp Crate Engine - Mopar Muscle Magazine
 
I put a set of Mickey Thompson Try-Y's on my 73 340 Challenger. No difference in performance. 9.75's in the 1/8th.
 
We all know that changing just one thing on a stock engine usually results in only a small improvement (intake, carb, cam, headers). I think a more interesting question is on a stock engine where is the biggest bottleneck limiting the making of more power or is it a waste of time only doing one thing? If you could only upgrade one component where is the money best spent or does it matter?

I know its 3x the $$ over the other upgrades but perhaps bolting on aluminum heads eliminates the biggest bottleneck (probably been tested already....I didn't search). I might have tried that with my latest stock build had price and availability gotten crazy.
 
1MeanA said:
We all know that changing just one thing on a stock engine usually results in only a small improvement (intake, carb, cam, headers). I think a more interesting question is on a stock engine where is the biggest bottleneck limiting the making of more power or is it a waste of time only doing one thing? If you could only upgrade one component where is the money best spent or does it matter?

I know its 3x the $$ over the other upgrades but perhaps bolting on aluminum heads eliminates the biggest bottleneck (probably been tested already....I didn't search). I might have tried that with my latest stock build had price and availability gotten crazy.
Click to expand...
That's only true IF you intend to make more power than the stock heads can flow.
 
abodyjoe said:
i never trust what a magazine prints. those numbers can be correct I don't know. what i do know is that magazines can and do make article results look however they want the outcome to look. who knows what or what they didnt do in that test.
Click to expand...
Yes cause they want everyone to run 360 manifolds instead of 340
 
I remember @IQ52 (Jim Laroy) did a dyno comparison between stock and HP manifolds years ago and found basically no difference. I believe Laroy Racing Engines knows what they're doing.

Here's what everyone is missing from my argument. Removing ALL variables.....in other words, NO engine, no NUTHIN, just long tube headers and manifolds on the flow bench. Headers win every time. Most people with the sense God gave a billy goat, if building an engine from the rip with headers WILL BUILD the engine to take advantage of them. In other words, single pattern cam, bigger than stock intake and carburetor possibly better heads, more compression and so on. Even if you have an existing build and just "slap some on" you WILL SEE more power as long as you TUNE for the headers. It's all in the tune. If you cannot and don't tune, it's entirely possible you won't see a difference. But that would be kinda stupid, wouldn't it?
 
Rat Bastid said:
I’m not going to bother reading that link so help me out. Are they using the OE cam? There are reasons why headers don’t make more power. One is most headers are JUNK and the second reason is improper cam timing.
Click to expand...
It's a stock 5.9 magnum including cam with 4bbl.
 
I can't give you horsepower numbers or fitment issues because I have a b-body however I have a mild Street 360 Magnum and went from hipo 340 manifolds to flowtech long tube headers and I could definitely feel more torque seat of pants. At the time I was running flowmaster mufflers and the sound was too loud for my taste. I switched to dynomax turbos and have a nice rumble at idle and good bark when I hit the fun pedal now. I used remflex gaskets and no leaks.
 
short answer is very little gain with headers..save your money.
...but you didn't want to hear that unless you're over 55.
 
ir3333 said:
short answer is very little gain with headers..save your money.
...but you didn't want to hear that unless you're over 55.
Click to expand...


What does age have to do with it? Absolutely nothing. Headed make power If they are good headers and your cam timing isn’t garbage.

Disputing this is idiotic.
 
If log exhaust manifolds were as good as it gets, why did all the manufacturers, I can think of, - make later style performance exhaust manifolds with individual, directional exhaust runners ?
Surely not for any scavenging, less restriction, lack of room, cost, weight, - reasons ? ?

How the hell some of you spend 1/4 the price of a good header to get 5 - 10 h/p (lol) outta an "X" or "H" pipe absolutely astounds me ! !
 
Last edited:
Most mods have pro's and con's

Does it add power you'll feel yes, is it worth it that's up to the individual.
 
The factories knew DAMN WELL that headers made more power. Ignorance abounds in this thread.

427 FORD HEADERS.jpg


PONTIAC HEADERS.jpg





MAX WEDGE HEADERS.jpg



HEMI HEADERS.jpg
 
I run 1968-70 340 manifolds on my 390 stroker and I am very happy with performance. I personally do not like headers. pain in the ***, ask Nick from Nick's garage!
 
I have this discussion with oldsters trying to recapture their youth, lol .
They remember the headers of old, leaking, dragging, spark plug access, ***** to install , - for the novice,
They sometimes balk when I include headers in the build, for all the old reasons .
I bring them into this century, guaranteeing no leaks, no ground clearance issues, etc. etc .
I check the flanges are true, or make them so.
Doug's, - - when they are on sale, - that simple, long tube equal length, tuned headers, true scavenging, no kitchen sink plumbing around the steering.
A 4 inch outlet on what used to be a 2 inch air pump !
Common sense !
Not a single complaint, not one ! !

And seriously, - with all that bitching, how often do you change plugs ? ?
Can't use that excuse with Doug's/TTI, plugs are easy access !
My plugs haven't been out in a coupla years, maybe 3 .
 
Last edited:
No arguments...most posts agree headers will add power...just a very small amount on a mild built or street driven car.
Now a 600 hp quarter mile piece would be different.
It is what it is!
 
justcuz said:
I have been told that the stock manifolds are free flowing and there would not be a huge power difference if upgraded to headers.

Would like to hear from members who have replaced their stock manifolds and if they noticed an improvement.
Click to expand...

What is your definition of HUGE. The question itself is vague.

Is 4-5% huge on a 300hp engine,or is it 10%, likely unattainable. That's the issue. Stock manifolds will not compete with even the junky 1 5/8 header when the carb and timing are tuned properly... which the magazine DID NOT do in that 360 manifold article. More camshaft than that ittty bitty stick and the gains increase across the board. It was swap item for item and run it. I bet the headers would show even more legs than the test results displayed. Headers make more power pretty much everywhere which is another benefit.

Basically if you had a car that was well sorted out with 300-310flywheel hp. it should run the the 12.85-12.90 range at 105-106

If headers were to provide about a 4-5% increase in power 12-15 hp, the car would run 12.60-12.65 at 108ish mph. If that isn't what you consider a huge gain, then pass on headers.

@inertia hit it on the head as well.
 
Last edited:
You must log in or register to reply here.
-

Back
Top