HP exhaust manifold verses Header comparison

[Cranky]

Have you ever driven a new car, 1970-1972 BB? They were fantastic. Mopar did them right. The exhausts were done to put out the most HP they could. Then WE took off stock exhausts, put on headers, and never could get them to run as good as they did with stock exhausts. Headers are also a clearance problem. So unless you build your engine, why use headers. I no longer use them. But do what you want since it is your vehicle.

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Never had a problem getting mine to run better. Grew up with these cars and drove them stock and modified. My mildly built 383 had no problem dusting off the factory 383 road runners and gave fits to 440 powered Chargers too. Had a lot of fun with that 66 4 door Belvedere pissing off the guys with their shiny new factory hot rods. Nutin like a sleeper
Btw, the 72's were nothing like the 70 model cars were....and only 2 engines were worth their salt in 71 when everything else went down in compression and power.

 

[Cranky]

Here is my Fatso

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Found a 4 dr version of that in the mid 70's with a 383 for the unheard of price of 250 bucks and it was running and ran pretty good.

It's all good buddy, taste is only what pleases you. As you get older what you think and like takes over gradually and you care less and less what others think. I could go further and say what I don't like and would prefer on your car but it doesn't matter as you like what you have. All the best to you.

You said a mouth full!

I just put my 68 road runner manifolds on the scale
RH is 17 lbs
LH is 19 lbs

PS I turned down $400 about 10 years ago--some day they will be going on my 67 R/T

Close to 40 lbs.....irrc, a BB head is close to 40 lbs.

I've ran headers on just about everything I've owned all the way into the late 90's. Think in all that time there's only been two burned wires and that was my fault. Thing is, even a cast iron manifold will burn one if it's allowed to lay on it. Also can say this....with cheap headers, a very large flat file is your friend! Once learning how to use one, header leaks were a thing of the past. Most of my street cars were mild builds and many still had the stock cam even but they got an intake, carb and header swap along with attention to timing and carb tuning. All of them ran better and all had a better butt feel and also showed a better ET slip than before the changes.

 

[Turboomni]

Spend money on your HP manifolds....

https://www.extrudehoneafm.com/

I did some research on this and the bottom line I found is that this process is indiscriminate and usually does not help that much and makes the exhaust manifold weaker and more prone to cracking.

 

[steve340]

My view is headers or manifolds really boils down to your own preference and what the car is used for - or the look you want. I have ported exhaust manifolds on a couple of factory high performance engines were the owner wanted the stock look. Time consuming and messy but I am sure they would have worked better.
If you are after power or have a big engine I would always go with a header.
I have a set of the shorty TTI ones on my 340 and was surprised how well they work.

 

[Kern Dog]

These debates always bring out guys that claim that their cars run great with the manifolds. They are rarely ever the guys with solid lifter cams, adjustable valvetrain, aluminum heads and higher than stock compression. Making power with exhaust manifolds can be done but you are setting yourself up for a more difficult situation. You can drive your car with tires set to 10 psi and still go fast but why? Good headers allow you to have better performance and a maintenance free operation.
I run TTI headers in my Charger and I have never burned a plug wire in 20 years and only burned a gasket once when I let the bolts back off. GRound clearance is not as good as with manifolds, I will concede that. I've never burned out a starter.
Yes, you can build an engine to run strong using cast iron manifolds BUT that same engine would make more power with headers.
The guys that claim that manifolds are just as good as headers in a performance engine are just ignorant of the facts. I've talked to these people at car shows. So far, every one of these guys are the type that either don't have a car or don't have a fast car. You've met these guys too.

 

[Robert Schaad]

I think the use of manifolds is likely to cost 20-30 HP.
The loss would be more as you revved the engine higher.

I think that would depend on the engine and what was done to it. Headers alone will not increase HP that much. If you build your engine, yes Headers play a role. HP exhaust manifolds were designed by MOPAR to give the maximum HP your engine can pump out. Stock Engine. Headers many times cause more problems then they are worth. Clearance problems and heat, burn cables, overheat starters. The answer to any question is: How do you feel about headers? It is your car so your decision is not right or wrong.

 

[Don selleck]

I ran hp manifolds on my recent build just tired of headers, there a pain in the ***. I'm not concerned about a little h.p. I'm not racing this one just a good cruiser. if i was needing h.p. then it would be a different story, just depends on what you want or need, and yes my headers are still hanging on the wall, just in case.

 

[Turboomni]

For me if I wanted to street race or drag race I would not own a 19 1/2 ft 4100 lbs Fury!!

 

[Dennis H]

Still want to know WHO would not want less weight and heat? Headers bring both.

 

[Robert Schaad]

I ran hp manifolds on my recent build just tired of headers, there a pain in the ***. I'm not concerned about a little h.p. I'm not racing this one just a good cruiser. if i was needing h.p. then it would be a different story, just depends on what you want or need, and yes my headers are still hanging on the wall, just in case.

Totally agree. I see some posts get upset if anyone makes any statement about headers. The use of Headers is up to the owner of a vehicle. I mention stock engines when I talk about using stock HP exhausts. Some members over look that I am saying stock. Of course building an engine could require headers. But that fact remains that Headers do cause clearance problems. But if one never has to work on his/her car, headers may be great. I do all my work and headers have always gotten in my way. Good luck with your car, love Chargers. I had a 68 with a factory 4 speed. Traded it before I knew what it was possibly worth.

 

[Robert Schaad]

Still want to know WHO would not want less weight and heat? Headers bring both.

The answer to your question is simple. What does the owner of any car want? I have used headers in several cars and they were a complete pain in the butt. Unless you are building a totally bad *** car, race car, weekend driver, then headers may be your choice. But to the average driver, ME, I drive my car daily and have had bad outcomes with headers. So the savings of weight is not important to me as much as the ease to work on my engine with stock exhausts. Hope that answers your question.

 

[Dennis H]

The answer to your question is simple. What does the owner of any car want? I have used headers in several cars and they were a complete pain in the butt. Unless you are building a totally bad *** car, race car, weekend driver, then headers may be your choice. But to the average driver, ME, I drive my car daily and have had bad outcomes with headers. So the savings of weight is not important to me as much as the ease to work on my engine with stock exhausts. Hope that answers your question.

90k street miles since headed install. No issues.

 

[moparedtn]

Still want to know WHO would not want less weight and heat? Headers bring both.

I don't think any would argue those points, Dennis - the debate is (and has always been, really) the
price one pays for 'em. The better the quality of the headers, the less that price is typically.
A minor second factor in the decision is the desire to retain the image of originality (in some cases)
and/or the ease of working on the engine with them installed (raises my own hand here).

I've had cars with both. Depended on the car as to what was chosen for each; this one, the thing came
with Hedmans and full 3" all the way back, which has not only been a colossal pain in the *** to work with
from one end to the other - but stubbornly refuses to rot out so I can justify replacing it all with good stuff.

 

[Billccm]

Been watching and reading and really didn't want to join the debate, but can't resist. My own experience with two different big block MOPARs was the headers always leaked. Now I will admit that was before I discovered REMFLEX gaskets, but those days of always fighting exhaust leaks turned me off. I was actually quite pleased when I went to look at my Road Runner and saw regular HP exhaust manifolds. I am happy with things as they are and will not change.

Maybe apples and oranges here, but back in the late 1970s my neighbor and I put headers on his 1975 455SD Trans Am. It leaned the car out, and we played around with the carb. Took it to a shade tree mechanic that drag raced Pontiacs and he got it running good, but the off the line was never as good as with the stock exhaust. Maybe we needed more tuning as we were young teenagers still learning?

Probably my old age speaking here, but I really like close to stock under the hood. No I am not a purist, and I like aftermarket upgrades, but the closer to stock seems to be more reliable and livable.

Now after saying all that there is a certain GTX with solid lifter 440 and headers that I really would like to have in my garage..………………..
@threewood

 

[BSB67]

So far, every one of these guys are the type that either don't have a car or don't have a fast car.

Except me.

 

[Cranky]

Headers are just one piece of the puzzle package. At a minimum better flowing mufflers, a better intake and a good carb should be used when you're going to install headers. I agree that just installing headers without the other parts to compliment them is usually not the best plan.

 

[Kern Dog]

HP exhaust manifolds were designed by MOPAR to give the maximum HP your engine can pump out.

This is a perfect example of the ignorant comments that I see online and hear at car shows.
No, the factory used exhaust manifolds for cost, durability, noise and fitment reasons. The HP manifolds barely flowed more than the log manifolds. A 350 HP 440 and a 375 HP 440 differed by a few small changes: Camshaft and valve springs, windage tray, dual exhaust and the HP manifolds. IN all that, they gained 25 HP. I doubt the HP manifolds made even 5-7 HP difference. There have been numerous tests on totally stock engines that have showed gains of 20 HP and more just with a header swap. This completely contradicts what you have written. Sorry to be so harsh but you are either stubborn to admit the truth or just ignorant on the subject.
Even the famous 1968-71 340 manifolds are barely worth 7 HP over the smaller 318 log manifolds. This has been tested in Mopar MUscle magazine about 15 years ago.
Manifolds lack the ability to scavenge the cylinders, one of the main benefits that headers provide. This is basic science that the exhaust manifold fan boys do not understand. Scavenging works on all engines but admittedly, they do work better as the camshaft timing gets further away from stock. Scavenging is the act of exhaust pulses passing through the collector creating a vacuum effect on the next exhaust pulse. This is essentially a means of better breathing not just through a reduced amount of flow restriction but instead a sort of mechanical encouragement to exhale faster and easier.
If these guys would just admit that they are happy enough with the performance they get with their manifold equipped engines and quit making uneducated and false claims, I'd respect that.
Again, there are guys that have fast cars that use cast iron manifolds but they do it in spite of the manifolds, surely not because of them.

 

[Kern Dog]

Maybe apples and oranges here, but back in the late 1970s my neighbor and I put headers on his 1975 455SD Trans Am. It leaned the car out, and we played around with the carb. Took it to a shade tree mechanic that drag raced Pontiacs and he got it running good, but the off the line was never as good as with the stock exhaust. Maybe we needed more tuning as we were young teenagers still learning?

From memory, the 455 was a 7.6 to 1 compression engine that had very mild cam timing and was designed to substitute cubic inches for the lowered compression and cam timing. A 400 built with 9.5 compression and a RA IV cam would smoke a 455 easily. The 75 455 was the first one with a catalytic converter so putting headers in front of such a bottleneck would be counterproductive. The mid 70s engines usually peaked at under 4000 rpms as well.

 

[Demonic]

interesting, have you had this done? and if so $$$? thanks

No personal experience. They made a splash several years ago with a few articles in car magazines, Mopar Action among them. The Factory Appearing Stock Tire guys purportedly are a fan of the Extrude Hone process. The inside of the manifolds come out very smooth, helping flow. It is not cheap.

The bottom line is this - there's no one number for how much HP gain you will get from headers. If you build a mild motor, near stock, with a cam around .470" lift, HP manifolds would be fine. If you build a big honkin' stroker with a big cam, 10.5-1 compression, aluminum heads, etc, the exhaust flow potential would be best served by good headers. It all has to match.

Data- it's a very, very mild 350, done by Hot Rod in 1995.
http://www.sweptline.com/tech/engine3.html

Other info:
https://boneheadperformance.com/extrude-honing/

https://books.google.com/books?id=k...ining cylinder head performance gains&f=false

https://www.challengertalk.com/threads/is-extrude-hone-worth-the-money.53078/

https://www.hotrod.com/articles/mopp-0104-buildup-1969-440-magnum-engine/

 

[BB BELLA]

I don't think you get the mopar "blat" from headers that you do from manifolds! Nothing sounds better than brand new headers and mufflers at an idle, except a BBmopar with manifolds when you chop the throttle at 5K!