Headers vs HP Manifold

Posted By: ramman5600

Headers vs HP Manifold - 11/04/11 03:34 AM

I have heard that the Original HP manifolds flow really well (much better than brand x original equipment), so I was wondering on a stock BB/RB engine is there any real advantage. I have run headers on most of my other cars (non-mopar) but as stated their original stuff flow like a clogged toilet. Thanks for the advice.

-C

Posted By: RapidRobert

Re: Headers vs HP Manifold - 11/04/11 05:12 AM

I've debated this myself whether to mess with headers. Andy made 550 HP w his 470 with HP manifolds/3" mandrel pipes. Way back "Headers by Ed" sold header kits and some custom headers and they quoted an independant study by Hot rod iirc that found a great amount of gain by utilizing equal length pri pipes and that was their big selling point and that's the only thing pushing me toward considering headers as opposed to the HP manifolds or maybe the max wedge manifolds which are even better and have a 3" flange outlet. The BB logs I wouldn't even consider

Posted By: Jim_Lusk

Re: Headers vs HP Manifold - 11/04/11 05:18 AM

Headers WILL add horsepower, but with a mild engine the increase is less dramatic. Cast iron manifolds will leak less and keep underhood temps down. I have never run headers and likely never will as I am not looking for every last bit of power.

Posted By: DaytonaTurbo

Re: Headers vs HP Manifold - 11/04/11 07:49 AM

On a stock engine, if you already have the HP manifolds on it, I'd just leave them be. I have headers on mine but my 440 is modded and had the log manifolds on it when I bought the car.

Posted By: DennisH

Re: Headers vs HP Manifold - 11/04/11 01:03 PM

TTI's. Less weight. Cooler.

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/04/11 01:48 PM

depends on what you have. ANY header will gain HP over Mani's. If you have a mild 440 and the exhaust is already on, I'd leave it alone.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 04:25 PM

Ahhhh, the old headers vs. manifolds discussion.

OK, why not?

- yes headers will usually show a gain over manifolds. how much depends on the motor/build. Expect maybe 10-15 on a street RB.

BUT

- most people fail to consider that the exhaust system is a SYSTEM and the motor doesn't really care WHERE the restriction is. I am positive that my HP manifold/2 1/2 " mandrel bent TTI/Dynomax Ultraflow system flows better than a set of cheapie headers mated to the stock exhaust system.

- People tend to look at this two ways; one person will say why give up the hp using manifolds and another will say that you can get whatever hp you are after using manifolds with the right build. Both are usually correct: it depends on your perspective.

Headers vs. Manifolds

pros - flow better, usually pick up some hp, lighter

cons - most leak, higher underhood temps, full headers can drag, doesn't look stock.

As was said; 500hp can easily be had with manifolds....how much power are you looking for?

Dave

Posted By: dogdays

Re: Headers vs HP Manifold - 11/04/11 05:26 PM

A common misconception is that headers only influence the top end.
Another common misconception is that headers only reduce power by reducing restrictions in the exhaust system.

Dyno tests have shown that shorty headers make more power than manifolds and long tube headers make more power than shorties. It has to do with the length of time the exhaust pulse travels in its own tube. A good long tube header will not only increase power above the torque peak, but it also increases torque below the torque peak. This low rpm increase clearly has little to do with flow restriction.

The oldsmobile head is an example. The center two exhaust ports are run together in the head and come out as one wider port which should lower restriction for those two ports. However, it is always advantageous to divide the ports. There is significant cross-talk between the two which interrupts something, probably scavenging during overlap. Flathead fords also had the center two exhast ports run together. In the flathead crowd it was a well-known modification to run a piece of sheet metal up that center port to divide the sides and increase performance.

There's more to an exhaust system than restriction.

R.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 06:50 PM

Quote:

A common misconception is that headers only influence the top end.
Another common misconception is that headers only reduce power by reducing restrictions in the exhaust system.

Dyno tests have shown that shorty headers make more power than manifolds and long tube headers make more power than shorties. It has to do with the length of time the exhaust pulse travels in its own tube. A good long tube header will not only increase power above the torque peak, but it also increases torque below the torque peak. This low rpm increase clearly has little to do with flow restriction.

The oldsmobile head is an example. The center two exhaust ports are run together in the head and come out as one wider port which should lower restriction for those two ports. However, it is always advantageous to divide the ports. There is significant cross-talk between the two which interrupts something, probably scavenging during overlap. Flathead fords also had the center two exhast ports run together. In the flathead crowd it was a well-known modification to run a piece of sheet metal up that center port to divide the sides and increase performance.

There's more to an exhaust system than restriction.

R.

I am aware of all that, yet my observations are still correct. I presume that you meant to say "increase power by reducing restrictions". Restriction isn't the ONLY part of the equation.....but it is the most important part, esp. when comparing relatively restrictive stock exhaust systems.

Dave

Posted By: dogdays

Re: Headers vs HP Manifold - 11/04/11 06:56 PM

Whatever.

http://www.moparmusclemagazine.com/techarticles/mopp_0106_manifolds_vs_headers/viewall.html

R.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 07:04 PM

Quote:

Whatever.

http://www.moparmusclemagazine.com/techarticles/mopp_0106_manifolds_vs_headers/viewall.html

R.

Read it all before.

- 1) Nobody said the headers wont make more power (all other things being equal)

- 2) How much power the headers are likely to add depends on the build and more importantly the cam. There is no way (for example) that headers would make that kind of difference on MY motor because MY cam is designed to make the HP manifolds work.

- 3) that test doesn't take into account the rest of the exhaust system. I've seen a good quality exh system and mufflers make almost .5 seconds difference. How many hp do you suppose that equates to?

......bottom line (as I said) isn't that headers make more power but rather that it has been proven that you can build a HP manifold equipped motor to equal that power level if that's your goal. As I said in my original post, it depends on your perspective.

Dave

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/04/11 07:15 PM

A manifold engine is like a one legged man in an a** kicking contest.
You can do whatever you want, but having two legs is always better.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 07:17 PM

Quote:

A manifold engine is like a one legged man in an a** kicking contest.
You can do whatever you want, but having two legs is always better.

just don't make the mistake of lining up against some of the manifold equipped cars in F.A.S.T. or it will be your a**

Dave

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/04/11 07:19 PM

Whats even scarier is a fast car with real headers.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 07:25 PM

Quote:

Whats even scarier is a fast car with real headers.

Yeah, you're right; a 383 with headers is the shiznit!

Dave

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/04/11 07:31 PM

Quote:

Quote:

Whats even scarier is a f.a.s.t car with real headers.

Yeah, you're right; a 383 with headers is the shiznit!

Dave

Sorry wasn't talking about my car. Reread the quote.

fastest I've gone with my motor is 130 ,, so I'm hardly in the same ranks

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 08:10 PM

Quote:

Quote:

Quote:

Whats even scarier is a f.a.s.t car with real headers.

Yeah, you're right; a 383 with headers is the shiznit!

Dave

Sorry wasn't talking about my car. Reread the quote.

fastest I've gone with my motor is 130 ,, so I'm hardly in the same ranks

I did reread your quote; you changed it from "fast" to "f.a.s.t." which changes the meaning......and of course there AREN'T any F.A.S.T. cars with headers......against the rules and all that.

anyway, have a good day.

Dave

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/04/11 08:22 PM

Quote:

Quote:

Quote:

Quote:

Whats even scarier is a f.a.s.t car with real headers.

Yeah, you're right; a 383 with headers is the shiznit!

Dave

Sorry wasn't talking about my car. Reread the quote.

fastest I've gone with my motor is 130 ,, so I'm hardly in the same ranks

I did reread your quote; you changed it from "fast" to "f.a.s.t." which changes the meaning......and of course there AREN'T any F.A.S.T. cars with headers......against the rules and all that.

anyway, have a good day.

Dave

Well I agree, when you have lemons, you make lemonade.
Here's to hoping your day is as good as mine

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 08:47 PM

Quote:

Here's to hoping your day is as good as mine

Thanks!

Where in Sask. do you live?; I was just in Regina and Moosejaw for meetings and to visit some friends not too long ago......nice place.

Dave

Posted By: d-150

Re: Headers vs HP Manifold - 11/04/11 09:02 PM

some motors i could not tell seat of pants difference some i could. i put shorty headers on my dodge v-10 truck and i think that was the biggest difference before barely peel out to smoking tires and tearing up the front band

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/04/11 09:27 PM

Quote:

Quote:

Here's to hoping your day is as good as mine

Thanks!

Where in Sask. do you live?; I was just in Regina and Moosejaw for meetings and to visit some friends not too long ago......nice place.

Dave

Saskatoon (saskaboom ?

). Yes very nice city , more importantly, the one with the race track. Last time I was in Kelowna was in the mid 80s. Now theres a nice city.
Just curious, do you know if your 'Bee was from here? A friend of mine sold one some time ago... he had 2 6 packs one auto, one 4 spd. Not sure which one he sold. He also has a concours pink 383 with white paint roof.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/04/11 11:50 PM

Quote:

Quote:

Quote:

Here's to hoping your day is as good as mine

Thanks!

Where in Sask. do you live?; I was just in Regina and Moosejaw for meetings and to visit some friends not too long ago......nice place.

Dave

Saskatoon (saskaboom ? ). Yes very nice city , more importantly, the one with the race track. Last time I was in Kelowna was in the mid 80s. Now theres a nice city.
Just curious, do you know if your 'Bee was from here? A friend of mine sold one some time ago... he had 2 6 packs one auto, one 4 spd. Not sure which one he sold. He also has a concours pink 383 with white paint roof.

Anythings possible; I was only able to track my car back 4 owners to about the early '90's. All I know is that it crossed the border into Canada in 2004 from Clovis Ca. and the last time the car appeared to have been driven was 1981 and that it had a California plate on it.

My theory is that the car was crashed in 1981 (body damage pass quarter, wheelhouse, bent axle, broken K frame). At some point in time it sat outside but not somewhere really wet as the body was solid.....then somebody tried a very poor attempt at an amature restoration (brazed up many of the underhood holes, hacked and brazed trunk floor replacment, spraybombed dash and gauges, 3 cast pistons and 5 forged ones......well you get the idea). Car then passed through several hands in the US and 2 more in Canada before I bought it and started throwing money at it like a drunken sailor!

Anyhow, if I get up your way, I'd love to

and maybe see your buddy's bee's.

sorry to everyone else for the

Dave

Posted By: mosweethemi

Re: Headers vs HP Manifold - 11/06/11 09:05 AM

Hello We have two 1970 Road Runners six pack car, Engines is the same, one has TTI headers ($835.00)and the other has stock manifolds,Both have 3" with 40s flowmaster all the way , one with chrome tips,one with turn downs,Both have 410 gears, one auto trans other 4 speed. The Stock manifolds car sound better and has more power then the header car! both cars have a H pipe also. Is it the stock manifolds ?All but one of the last 10 cars have stock exhaust and 3" pipes. MY

Is headers is for drag racing ,manifolds stock street cars 450-550 HP , no engine heat under the hood. no gasket troubles.no floor board heat, again

Posted By: Slipknot440

Re: Headers vs HP Manifold - 11/06/11 03:00 PM

my stock bore, stroke, iron block, iron head, single 4bbl, 9.1 compression hemi was dynoed with and without headers. 498 hp with manifolds, 511 with 3" headers. Already had 2.5" TTI exhaust from the former 440, so cutting up a new exhaust and dropping a $1000 on good coated headers just wasn't justifiable for 13 more hp. I also didn't mess with my starter or beat up my inner fenders like I have in the past with headers. Also, all the manifold cars i've ever had have never ran hot. All my header cars get a little warm for my taste and have ended up some type of leak.

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/06/11 03:33 PM

Quote:

my stock bore, stroke, iron block, iron head, single 4bbl, 9.1 compression hemi was dynoed with and without headers. 498 hp with manifolds, 511 with 3" headers. Already had 2.5" TTI exhaust from the former 440, so cutting up a new exhaust and dropping a $1000 on good coated headers just wasn't justifiable for 13 more hp. I also didn't mess with my starter or beat up my inner fenders like I have in the past with headers. Also, all the manifold cars i've ever had have never ran hot. All my header cars get a little warm for my taste and have ended up some type of leak.

I would hazzard a guess as the HP is restricted by the iron intake, carb, low compression and cam selection. Not the header or not to header. Also one doesn't need to spend $1000 on a set of headers.
As mentioned before if you already have the mani's and exhaust use it, if you are statrting from scratch and you want the most out of your engine get a set of headers. Some people here think they are the most complicated thing in the world for some reason. If you take your time even cheap sets can be installed w/o issues. ALL headers will be harder to install than mani's so keep that in mind.

Posted By: 4boxers4

Re: Headers vs HP Manifold - 11/06/11 05:26 PM

Header change is the number one, easy, build up trick in my opinion, for BB Mopar. I believe there is a Dulcich article valuing them from 25~40hp, depending on the engine specs.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/06/11 06:20 PM

Quote:

Quote:

my stock bore, stroke, iron block, iron head, single 4bbl, 9.1 compression hemi was dynoed with and without headers. 498 hp with manifolds, 511 with 3" headers. Already had 2.5" TTI exhaust from the former 440, so cutting up a new exhaust and dropping a $1000 on good coated headers just wasn't justifiable for 13 more hp. I also didn't mess with my starter or beat up my inner fenders like I have in the past with headers. Also, all the manifold cars i've ever had have never ran hot. All my header cars get a little warm for my taste and have ended up some type of leak.

I would hazzard a guess as the HP is restricted by the iron intake, carb, low compression and cam selection. Not the header or not to header. Also one doesn't need to spend $1000 on a set of headers.
As mentioned before if you already have the mani's and exhaust use it, if you are statrting from scratch and you want the most out of your engine get a set of headers. Some people here think they are the most complicated thing in the world for some reason. If you take your time even cheap sets can be installed w/o issues. ALL headers will be harder to install than mani's so keep that in mind.

Who says the horsepower is restricted? 500hp out of a pump gas, non stroker doesn't sound restricted to me! As far as the intake comment; you know this is a Hemi, right?

anyhow, even though the Hemi manifolds are better than the RB HP ones, this is a good example of a motor that obviously didn't benefit much from installing headers (even the good, expensive ones!)

Dave

Posted By: DaytonaTurbo

Re: Headers vs HP Manifold - 11/06/11 06:57 PM

Quote:

Quote:

my stock bore, stroke, iron block, iron head, single 4bbl, 9.1 compression hemi was dynoed with and without headers. 498 hp with manifolds, 511 with 3" headers. Already had 2.5" TTI exhaust from the former 440, so cutting up a new exhaust and dropping a $1000 on good coated headers just wasn't justifiable for 13 more hp. I also didn't mess with my starter or beat up my inner fenders like I have in the past with headers. Also, all the manifold cars i've ever had have never ran hot. All my header cars get a little warm for my taste and have ended up some type of leak.

I would hazzard a guess as the HP is restricted by the iron intake, carb, low compression and cam selection. Not the header or not to header. Also one doesn't need to spend $1000 on a set of headers.
As mentioned before if you already have the mani's and exhaust use it, if you are statrting from scratch and you want the most out of your engine get a set of headers. Some people here think they are the most complicated thing in the world for some reason. If you take your time even cheap sets can be installed w/o issues. ALL headers will be harder to install than mani's so keep that in mind.

You missed the part where he said this is a HEMI. There's no comparing 440hp manifolds to Hemi manifolds.

versus

Hmmm

Posted By: DennisH

Re: Headers vs HP Manifold - 11/06/11 10:21 PM

Ceramic polished million dollar TTI's are much cooler under the hood.

Posted By: RapidRobert

Re: Headers vs HP Manifold - 11/06/11 10:28 PM

Quote:

Quote:

A manifold engine is like a one legged man in an a** kicking contest.

just don't make the mistake of lining up against some of the manifold equipped cars in F.A.S.T. or it will be your a**

Posted By: dOrk !

Re: Headers vs HP Manifold - 11/06/11 10:29 PM

... they must be SNOWED IN ...up in cAnUcKaDa !!

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/07/11 12:23 AM

Quote:

Quote:

Quote:

my stock bore, stroke, iron block, iron head, single 4bbl, 9.1 compression hemi was dynoed with and without headers. 498 hp with manifolds, 511 with 3" headers. Already had 2.5" TTI exhaust from the former 440, so cutting up a new exhaust and dropping a $1000 on good coated headers just wasn't justifiable for 13 more hp. I also didn't mess with my starter or beat up my inner fenders like I have in the past with headers. Also, all the manifold cars i've ever had have never ran hot. All my header cars get a little warm for my taste and have ended up some type of leak.

I would hazzard a guess as the HP is restricted by the iron intake, carb, low compression and cam selection. Not the header or not to header. Also one doesn't need to spend $1000 on a set of headers.
As mentioned before if you already have the mani's and exhaust use it, if you are statrting from scratch and you want the most out of your engine get a set of headers. Some people here think they are the most complicated thing in the world for some reason. If you take your time even cheap sets can be installed w/o issues. ALL headers will be harder to install than mani's so keep that in mind.

Who says the horsepower is restricted? 500hp out of a pump gas, non stroker doesn't sound restricted to me! As far as the intake comment; you know this is a Hemi, right?

anyhow, even though the Hemi manifolds are better than the RB HP ones, this is a good example of a motor that obviously didn't benefit much from installing headers (even the good, expensive ones!)

Dave

ok...low output hemi and hemi manis. Ask the FAST guys if they'd like to run even small tube headers vs the manis. His motor doesn't need headers because of the low numbers, however if he had some cam a decent carb (or carbs) and intake the headers would add well more than 13hp. You can gain up to 38 more HP going from 1 3/4" to 2" in a semi-mild 440.

Posted By: RemCharger

Re: Headers vs HP Manifold - 11/07/11 01:32 AM

Quote:

You can gain up to 38 more HP going from 1 3/4" to 2" in a semi-mild 440.

Nothing wrong with manifolding-down a 550hp motor to 500. Its still nothing to laugh at. Me being the extremist that I am,,, would prefer the free- flowing version.
Again* nothing wrong with restrictive exhaust.

Posted By: 383man

Re: Headers vs HP Manifold - 11/07/11 06:03 AM

You can gain up to 38 more HP going from 1 3/4" to 2" in a semi-mild 440

I would be surprised to see that much gain.
I know CPPA had a test done years ago on a mild 440 and it was just as fast with the smaller 1-3/4 tubes as the 2" because it lost low end on the 2". To me the stronger engines will benifit more going with the larger tubes. I could be wrong but I didn't think it would make that much difference on a mild 440. Ron

Posted By: mopar_man

Re: Headers vs HP Manifold - 11/07/11 02:00 PM

, I wouldn't put headers on an outhouse. Absolute trash with no measurable gain on a street motor.
If your drag racing and need to get every scrap of hp available , sure go for it and they will increase hp but be prepared for leaks , excess heat , fried wires , etc etc

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/07/11 02:24 PM

Ron I didn't belive it either until I read t he Car Craft artical that somebody posted here. As a matter of fact I think it was 39. I don't have the link but I'm sure it can be googled w/o much effort.

Posted By: 383man

Re: Headers vs HP Manifold - 11/07/11 03:54 PM

Quote:

My , I wouldn't put headers on an outhouse. Absolute trash with no measurable gain on a street motor.
If your drag racing and need to get every scrap of hp available , sure go for it and they will increase hp but be prepared for leaks , excess heat , fried wires , etc etc

I dont know what headers you use but I have never had any of them problems. In fact the headers on my sons Dart have been on the car since 1997 and have never leaked or blew a gasket or burnt a wire. The same with my 63 as I have no problems at all using headers. They make much better headers now with thick flanges then the junk back in the 70's with paper thin flanges. I will take headers any day over manifolds on a performance car. Unless I ran a class where the rules make you run manifolds I will take the hp and use headers. Ron

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/07/11 04:32 PM

Quote:

Quote:

My , I wouldn't put headers on an outhouse. Absolute trash with no measurable gain on a street motor.
If your drag racing and need to get every scrap of hp available , sure go for it and they will increase hp but be prepared for leaks , excess heat , fried wires , etc etc

I dont know what headers you use but I have never had any of them problems. In fact the headers on my sons Dart have been on the car since 1997 and have never leaked or blew a gasket or burnt a wire. The same with my 63 as I have no problems at all using headers. They make much better headers now with thick flanges then the junk back in the 70's with paper thin flanges. I will take headers any day over manifolds on a performance car. Unless I ran a class where the rules make you run manifolds I will take the hp and use headers. Ron

like I said Ron some folks here think they are the hardest thing next to rocket science. Actually headers are a good cheap alternative to Hi-Po manis. Hi-Po manis can cost twice what a set of headers cost. If you go w/ headers you get the added benefit of MEASURABLE HP and MPG's if you care about that.

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/07/11 04:57 PM

Quote:

Ron I didn't belive it either until I read t he Car Craft artical that somebody posted here. As a matter of fact I think it was 39. I don't have the link but I'm sure it can be googled w/o much effort.

39 on one particular motor; sure. The reality is that you could gain anywhere between nothing and 100hp: it depends on the build.

It really isn't rocket science; the amount of power gained by switching to tube headers from manifolds depends on a number of things;

- the manifolds in question. Our HP manifolds are decent - better than GM BB manifolds and worse than Hemi or MW manifolds.

- where the other bottlenecks are; there isn't as much point in increasing exhaust flow on a motor that has a crappy flowing intake, heads, etc.

The best example of a motor that needs headers that I can think of is a 427 L88 BBC which due to it's restrictive factory manifolds, good flowing heads and a radical solid lifter cam can gain somewhere around 80 - 100hp with the swap. My guess is a stock street hemi or Max Wedge falls on the other side of the spectrum; the stock manifolds flow much better than their GM counterparts. An RB with HP manifolds falls somewhere in between......depending on how it's built. I would guess that a bone stock 375hp 440 Magnum would see a slight increase along the lines of 10-20hp......is that worth it? that depends on how you weigh the pros and cons; there is no right or wrong answer.

Dave

Posted By: Pyper70

Re: Headers vs HP Manifold - 11/07/11 07:15 PM

Anyone who says HP manifolds don't leak hasn't experienced an HP manifold leaking. I had one leak. Now place yourself in the middle of nowhere without a reputable machine shop. Now bust out the hand files and emery cloth and sit there for 10hours sanding down the entire flange of a 40 yr old cast iron manifold (happened 2 years ago).

I have purchased since then a set of plain jane hedman shorties which I sent out to get blasted and then Jet Hot coated. I do plan on installing them on my 440 I just haven't allocated the time yet. My 440..Nothing crazy..480 lift Isky, 10:1, Dual Quads, 727 with a gear vendors. I will say though that the 906s are coming off along with the HP manifolds and I am installing the Eddy heads that have been sitting on my shelf for 2 years.

Down the road, these Hedmans are going to get bolted with the same induction (dual quads, CH28, Eddy heads) to my 505 stroker. 4.15 crank, .540 Comp roller, H beam rods, 11:1 motor. I fear the only thing at that point weak in the system will be the trans but I do not lay into it at street lights, I don't do burnouts....I run down the line and chirp tires between gears. Hoping for 475hp on my 440 now and 575hp on my 505.

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/07/11 07:35 PM

"Anyone who says HP manifolds don't leak hasn't experienced an HP manifold leaking. I had one leak. Now place yourself in the middle of nowhere without a reputable machine shop. Now bust out the hand files and emery cloth and sit there for 10hours sanding down the entire flange of a 40 yr old cast iron manifold (happened 2 years ago)".

true that. They leak and when they do it stinks. I got to the point that I used exhaust mani gaskets on a few BB-mani combo's.

Posted By: 383man

Re: Headers vs HP Manifold - 11/07/11 09:40 PM

Quote:

Quote:

Ron I didn't belive it either until I read t he Car Craft artical that somebody posted here. As a matter of fact I think it was 39. I don't have the link but I'm sure it can be googled w/o much effort.

39 on one particular motor; sure. The reality is that you could gain anywhere between nothing and 100hp: it depends on the build.

It really isn't rocket science; the amount of power gained by switching to tube headers from manifolds depends on a number of things;

- the manifolds in question. Our HP manifolds are decent - better than GM BB manifolds and worse than Hemi or MW manifolds.

- where the other bottlenecks are; there isn't as much point in increasing exhaust flow on a motor that has a crappy flowing intake, heads, etc.

The best example of a motor that needs headers that I can think of is a 427 L88 BBC which due to it's restrictive factory manifolds, good flowing heads and a radical solid lifter cam can gain somewhere around 80 - 100hp with the swap. My guess is a stock street hemi or Max Wedge falls on the other side of the spectrum; the stock manifolds flow much better than their GM counterparts. An RB with HP manifolds falls somewhere in between......depending on how it's built. I would guess that a bone stock 375hp 440 Magnum would see a slight increase along the lines of 10-20hp......is that worth it? that depends on how you weigh the pros and cons; there is no right or wrong answer.

+

Dave

Actually I may have misled some as I thought Mr Yuck meant 39 hp going from 1-3/4 headers to 2" headers not from manifolds. And he may well be right as it just seemed like alot for the header upgrade. Sorry if I misled anyone. Ron

Posted By: DPelletier

Re: Headers vs HP Manifold - 11/08/11 12:07 AM

Quote:

Actually I may have misled some as I thought Mr Yuck meant 39 hp going from 1-3/4 headers to 2" headers not from manifolds. And he may well be right as it just seemed like alot for the header upgrade. Sorry if I misled anyone. Ron

Perhaps not; rereading the posts, maybe you were right and they meant 39hp between 1 3/4" and 2" headers.

All I know is that is way more that I would think is possible on a stockish/street style 400 -450hp build. On a 500-600hp motor, maybe.

Dave

Posted By: Mr.Yuck

Re: Headers vs HP Manifold - 11/08/11 12:40 AM

Quote:

Quote:

Actually I may have misled some as I thought Mr Yuck meant 39 hp going from 1-3/4 headers to 2" headers not from manifolds. And he may well be right as it just seemed like alot for the header upgrade. Sorry if I misled anyone. Ron

Perhaps not; rereading the posts, maybe you were right and they meant 39hp between 1 3/4" and 2" headers. All I know is that is way more that I would think is possible on a stockish/street style 400 -450hp build. On a 500-600hp motor, maybe.

Dave

it was header vs header. and it was here maybe a week ago. I'll see if I can find it.