HP manifold performance

[superbird77]

I was wondering about the performance of the stock HP exhaust manifolds that came standard on roadrunners, etc. I know there have been some tests done and the general consensus is that headers out perform the manifolds by a good margin. The reason i ask is because i was watching the show graveyard cars and the owner (who is almost unwatchable) stated that the HP manifolds perform as good as headers. It was part of a true or false segment. Based on his opinion i got it wrong and i was sure the tests proved headers to make more power.

Does anyone have any insight on this? Seems the tests would be the final word but he was sure that wasnt the case. I know this has been discussed before but i wanted to see if anyone agreed with his statements.

 

[AMX364]

At lower rpm stock HP manifolds work as good as headers (below 3,000), after that headers work better. However, ever change a starter with headers outside in sleet and you will not like it!

 

[440beep]

Trying to do anything with headers on is a PIA. I saw the same segment on Graveryard and was wondering the same thing since I'm sitting on a pair of HP mainfolds. The performance difference between the two was unbelievable when I switched over to the 2" headers though, sure woke the car up!!!!

And yea, that Mark guy totally ruins an otherwise decent show. I have to watch the show with the "mute" button on since I can't stand that freaking guy and every time he opens his mouth.

 

[lewtot184]

headers should add 20-30hp in a modest build. this becomes more critical as valve overlap and duration are increased. there are those who are die hard exhaust manifold people, i'm not. they both have a place but as engine modifications increase exhaust flow is more critical and the manifolds will be a restriction. they are ways to build for the use of cast manifolds.

 

[superbird77]

I just thought it was odd for him to say that and mention the tests. I guess the key is below a certain RPM, the car i am building is a street car but i would like to maximize its potential. Maybe shorty headers are a good compromise.

 

[440beep]

My car's a street car, and I put the TTI 2" headers/3" exhaust on and what a difference it made even on the street. I got the 2" headers in anticipiation for the new motor that's in it now, but even on the old motor it was noticeable going from the HP manifolds (it probably also helped going from the 2.25" exhaust to the 3").

 

[Dennis H]

TTI's. Ceramic. Heat and weight reduction alone are worth the change. Get your wallet.

 

[superbird77]

Yeah, the TTi's are pricey to say the least. Anyone running shorty versions?

 

[Gpuller]

A member over at DC.com dynoed his 512 with manifolds and small 1 5/8" headers that the dyno operator had laying around. I'm sure that the small headers were choking it a bit. I was surprised at the torque numbers.

Headers:
525 HP @ 4800
629 TQ @ 4300

Manifolds:
521 HP @ 5300
575 TQ @ 4200

http://www.dodgecharger.com/forum/index.php/topic,64302.0/all.html

 

[ZR9B]

Can the HP manifolds be ported? Just wondering as I'm sick of headers over here.

 

[67 coronet]

choke point on the manifolds is the pipe flange.its just too small to allow any real good flow.headders are much better.dont get me wrong,on a mild street motor they will be fine.if you are looking to build any real power go with the headders.

 

[lewtot184]

Can the HP manifolds be ported? Just wondering as I'm sick of headers over here.

i don't think there's much to be had with porting. i've looked at this and didn't find much to go after. extrude-a-hone is a small gain for a bunch of money. there simply isn't enough volume in the manifolds and that crummy right angle turn off the ports on the passenger side and the mess were #7 enters the pipe flange. if you look at some of the hipo chevy big block and earlier 427 ford manifolds for instance i just don't understand the love affair for mopar manifolds. i quit drinking the kool-aid years ago.

 

[Meep-Meep]

No way are manifolds as good as headers, so if you want to get the most out of that cam, don't choke it up with manifolds. And I'm not saying you can't get good power numbers with manifolds, because you can. It's just headers will make even more power.

 

[lewtot184]

i have a '69r/t with manifolds and a '65 coronet with 2" tti's. sometimes i think its easier to change plugs with the header car than the manifolds car. i've never really understood the problems some people have with headers. i don't know if it's what they buy or how they do the installation that is such a problem. one thing for sure; never use header bolts on iron heads and wet holes, always use studs. i make my own spark plug wires so that i don't have wire/header/heat issues. having the proper tools for maintenance is always a plus.

 

[Cranky]

Can the HP manifolds be ported? Just wondering as I'm sick of headers over here.

What brand of headers have you dealt with and what were the problems? Had a set of Hooker Super Comps on my 71 340 Cuda and they lasted over 15 years with no problems.

 

[ZR9B]

What brand of headers have you dealt with and what were the problems? Had a set of Hooker Super Comps on my 71 340 Cuda and they lasted over 15 years with no problems.

super comps on a 440...the super comps I had as a kid were no problem on my 70 340 Cuda... but these just seem thin and you can hear the metallic sound...not to mention the heat. never a problem with starters, plugs, wires or any of that.

 

[tallhair]

A member over at DC.com dynoed his 512 with manifolds and small 1 5/8" headers that the dyno operator had laying around. I'm sure that the small headers were choking it a bit. I was surprised at the torque numbers.

Headers:
525 HP @ 4800
629 TQ @ 4300

Manifolds:
521 HP @ 5300
575 TQ @ 4200

http://www.dodgecharger.com/forum/index.php/topic,64302.0/all.html

I've read that smaller pipe diameter headers are actually better for torque on a street cars RPM range than larger diameter and that larger diameter ones like 2" reduce torque and allow back pressure at lower RPM ... but more like 1 7/8s for BB would probably be better

 

[coloradodave]

This is not a sensible comparison. 1 5/8" headers on a 512" big block are ridiculous. Put a set of 2" TTIs on that motor and then compare the numbers. As for the link, the fellow with the 68 Charger wants to use the stock manifolds on his #s matching car for originality, but is going to use 3" exhaust with an X pipe. Like some here have said, if the motor is stock or close to stock, no problem using the cast manifolds. But, if you're looking for maximum efficiency and performance, headers are the way to go. Shorty headers are mostly made for installation convenience. I've seen them for trucks but don't recall seeing them for B bodies. Do some reading on the scavenging effects of long tube headers, tubing size verses cubic inches and intended RPM range. Manifolds have their place but if you check out any serious race cars, where they have a choice, you'll see headers. No EXPERT will argue that manifolds and headers are equal in producing horsepower or torque.

 

[Cornpatch MO]

I was wondering about the performance of the stock HP exhaust manifolds that came standard on roadrunners, etc. I know there have been some tests done and the general consensus is that headers out perform the manifolds by a good margin. The reason i ask is because i was watching the show graveyard cars and the owner (who is almost unwatchable) stated that the HP manifolds perform as good as headers. It was part of a true or false segment. Based on his opinion i got it wrong and i was sure the tests proved headers to make more power.

Does anyone have any insight on this? Seems the tests would be the final word but he was sure that wasnt the case. I know this has been discussed before but i wanted to see if anyone agreed with his statements.

I too watched that show, altho I don't think I could stand to be around that guy, he does seem to know a lot about Mopars. I was interested in that manifold question as I will be useing the stock 68-69 H P exhaust manifolds. I have been trying to think what the rest of his story is--possibly compared to headers available in those years? Maybe just an outrageous statement so people would think is is total GURU 8-) .................MO

 

[Garys1969RR]

Installing headers and replacing the ported 906 heads with ported 915s got me almost a full second of my ET in the 1/4 mile. 69 RR with 451, auto trans. Who know how much improvement was due to the head change, and how much was due to the header installation. I know they both helped. Don't know what the guy on tv was thinking, but headers have always been a great way to increase power and torque.

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And I was using open exhaust with the stock 69HP manifolds, as well as with the headers.