The header / Exhast manifolds Debate

feitctaj · Apr 11, 2005

OK lets talk Headers Vs, Exhast manifolds, I think that many here have an opinion,
I too have stated my opinion, and many have given good info, to rebut it.
My opinion has always been that of this board, very few RACE their bronco. So I have my opinion that most do not have motors that run often above 4500 RPM for long periods .
Thus I would add that a set of headers would not give these motors a large advantage after adding headers, ( MY Opinion)
Also it does make me crazy when folks give dyno data out of a Carcraft or performance mag that has big ass ads to sell you headers in the back. Mmmm that would chase advertisers away, if you did a test in the dyno room that did not reflect good of one of your advertisers.
And I also submit that speedshops don't make money telling you that headers will not help your rig in some way. Afterall magazines and rodshops are not there to lose money.
OK, so enough about my opinion, hows about some data?
I found one site that had some data(Ofcourse , it backed up my previous claims of only a 3% increase from adding headers %) , you think my ego is that small?)
This is a site about a 455 olds , I could not find data from a SBF that was not backed or submited by someone or group, afiliated or represented by a header company.
The data states very clearly that 3% is the norm. Bear with me the data is faded and hard to read(they must not have gotten a check from Hooker).
When I post this , I am not trying to anger anyone, I just like to gather data in my spare time and wade through what I call the attack of the advertisers.
Also , I aint the computor wiz , so those that can help with the data, are welcome OK ,,,,,?

Brewbro21 · Apr 11, 2005

This "could" be some good info, however we need to look in the gray area here. What was the engine that they tested? If you put headers on a stock engine your gains will be minimal. However you put headers on a modified, wheather it be heavily or slightly and gains improve with the mods. so we should take that into consideration. Also what was the rest of the exhaust like? Stock or mods.?

Is there a table or something that says what the engine is or was?

feitctaj · Apr 11, 2005

Brewbro21 said:
This "could" be some good info, however we need to look in the gray area here. What was the engine that they tested? If you put headers on a stock engine your gains will be minimal. However you put headers on a modified, wheather it be heavily or slightly and gains improve with the mods. so we should take that into consideration. Also what was the rest of the exhaust like? Stock or mods.?

Is there a table or something that says what the engine is or was?

http://www.gmccoop.com/koba_built_motors.htm
I don't believe that the % goes up above 5% on even a Highly modified motor, yes headers /tuned exhast, are better on a very high performance motor, but again, how many here have a 400 HP motor?
This is Math.
I gave the 3% figure over a year ago and this is not a guess on my part, that is data there.

69patriot76 · Apr 11, 2005

I'm sorry, but I didn't read your data. I have headers because they make me a better man.

feitctaj · Apr 11, 2005

69patriot76 said:
I'm sorry, but I didn't read your data. I have headers because they make me a better man.

roflmao

AT LEAST YOUR HONEST

76Broncofromhell · Apr 11, 2005

I will concede that headers will not do too much in the performance realm for your smogged 302 in a 73-77 Bronco. The biggest change will be in the sound in the pipes not the performance.

With that said, if you have a high performance engine the manifolds can hinder horsepower and that is why headers help power. On my 408, I noticed a difference when I swapped my 2.25 pipes out for 2.5" pipes. I think the 408 would be a dog if it had exhaust manifolds.

One of us needs to get a hold of a dyno and settle this for SBFs.

j.r.nice · Apr 11, 2005

SBF biggest downfalls is the retrictive exhaust. Of course this is primarily due to the head design and small exhaust valves. I would guess that adding headers is probably one of the better mods (especially to a SBF) and would add at least 5% on a stock 302.

Weight savings is also a consideration. Of course on a 3800-4000 lb Bronco what's a couple more pounds!

68ford · Apr 11, 2005

money come to play in my mind, even if you have a stock motor amd say you need new manifolds or new headers, arent headers cheapr and more readily available? i wouldnt go out of my way to find used manifolds when i can get new ones from summit for 100 bucks and possibly make 5 to ?????? hp. if your stock and hve them spend money elsewhere, if you need one or the other, just get headers and get the benifit even if its small.
personally i feel that if you have a 4 barrel, intake and even small cam, headers are a no brainer. thats just my 2cents though.
i am one of those guys who races with 350hp and rarely go under 4000rpm while on the track ;D

68ford · Apr 11, 2005

just a thought, on a small stroke motor like ours where the velocities are significantly less than stroker motors(or long stroke motors like the 455), would having the least restrictive intake and exhaust be more important or less? ?:?

feitctaj · Apr 11, 2005

68ford said:
money come to play in my mind, even if you have a stock motor amd say you need new manifolds or new headers, arent headers cheapr and more readily available? i wouldnt go out of my way to find used manifolds when i can get new ones from summit for 100 bucks and possibly make 5 to ?????? hp. if your stock and hve them spend money elsewhere, if you need one or the other, just get headers and get the benifit even if its small.
personally i feel that if you have a 4 barrel, intake and even small cam, headers are a no brainer. thats just my 2cents though.
i am one of those guys who races with 350hp and rarely go under 4000rpm while on the track ;D

ok then if we follow your line of thinking is the price of headers worth 6 to 10 HP on a stock 200 HP MOtor?

feitctaj · Apr 11, 2005

68ford said:
just a thought, on a small stroke motor like ours where the velocities are significantly less than stroker motors(or long stroke motors like the 455), would having the least restrictive intake and exhaust be more important or less? ?:?

good question, but I do not know. let me think about it over night and find some data.

feitctaj · Apr 11, 2005

j.r.nice said:
SBF biggest downfalls is the retrictive exhaust. Of course this is primarily due to the head design and small exhaust valves. I would guess that adding headers is probably one of the better mods (especially to a SBF) and would add at least 5% on a stock 302.

Weight savings is also a consideration. Of course on a 3800-4000 lb Bronco what's a couple more pounds!

my figures that I came up with were just math that was the norm for the industry since the 30s, And I do not see haow you can say that a 302, stock would have 5% increase in power if the 455 has 3% , got any data? and please , not another study by carcraft, Ok. also this is dyno stuff the weight of the vehicle has nothing to do with the subject.

feitctaj · Apr 11, 2005

76Broncofromhell said:
I will concede that headers will not do too much in the performance realm for your smogged 302 in a 73-77 Bronco. The biggest change will be in the sound in the pipes not the performance.

With that said, if you have a high performance engine the manifolds can hinder horsepower and that is why headers help power. On my 408, I noticed a difference when I swapped my 2.25 pipes out for 2.5" pipes. I think the 408 would be a dog if it had exhaust manifolds.

One of us needs to get a hold of a dyno and settle this for SBFs.

You see hell , that is my point, there are not many on this site that have motors like you, most have mid to medium motors. If you have the power that you claim( I am not doubting you) you have not just bolted not the power there (I am asuuming ) Many mods not just a cam headers carb, there are many spendy mods to get to where you have brought your rig to.
, that is my whole point, right rthere,I need to see the data, I really dought most that have headers and a mild cam can tell better than a Dyno. I can see many small mods add up to big power increases. But not more than 3% for a set of headers.

69patriot76 · Apr 11, 2005

I'm still feeling manly.

69patriot76 · Apr 11, 2005

At the end of next week I will post the results of the dyno for my 302 after I finish building it. (600cfm, intake, ported and polished heads, decked block, 270 duration cam, and lest we not forget... headers) I know it's not a stock 302, but, I'll have the little weenie/big dyno results! I'll even see if I can round up some stock manifolds to swap out to check the difference.

I'm so manly, oh so manly, so manly and witty and hmmm... ;D

SnwMnkys · Apr 12, 2005

Are there any specs on the headers in that comparison theyre doing? If the headers are running 1 1/2" tubes and a dinky collector on a 455 CI motor, then yes theyre not going to see a big increase.

68ford · Apr 12, 2005

69patriot76 said:
At the end of next week I will post the results of the dyno for my 302 after I finish building it. (600cfm, intake, ported and polished heads, decked block, 270 duration cam, and lest we not forget... headers) I know it's not a stock 302, but, I'll have the little weenie/big dyno results! I'll even see if I can round up some stock manifolds to swap out to check the difference.

I'm so manly, oh so manly, so manly and witty and hmmm... ;D

if i remember corectly, your motor is real similar to mine, i thought your was a 347 though? but anyway mine has same stuff but heads are machined to fit big chevy valves, my motor turns 7000rpms regularly, so i think we are not fair in this comparison.
i agree that it would probably be a waste if your motor was stock, i just meant that if you had neither or bad manifolds, i would just buy new headers instead of trying to find, then spend money on used manifolds.

cjjhalfcab · Apr 12, 2005

I've always been under the understanding that headers are better for all around efficiency, not just power. The internal combustion engine is just one big ass air pump, and headers help it to flow the outgoing air at a more efficient rate. Not only can they improve power, but fuel economy as well. Not sure of the gains on a 302 or 351W, but I know for a fact that there is a major difference on a 351C with or without headers - and the tube size is critical. I had a Cleveland with 1-5/8" tube headers on it, and it had a ton of low end (and yes, it was the 4V head variety). Put the stock manifolds back on it and it fell flat on it's face. I'd have liked to have seen the difference in torque on a dyno between the two. I think tube size on all engines should be taken into consideration; just like the carb, people tend to way over-do it on tube size. Unless you're going to constantly be running very high RPMs, 1-3/4" tubes and an 1150 Dominator on a 302 is very unnecessary. I'd also like to see on a dyno the difference between full length and shorties. Bottom line: if you want 'em, get 'em; if not run the manifolds. They both work just fine.

j.r.nice · Apr 12, 2005

feitctaj said:
my figures that I came up with were just math that was the norm for the industry since the 30s, And I do not see haow you can say that a 302, stock would have 5% increase in power if the 455 has 3% , got any data? and please , not another study by carcraft, Ok. also this is dyno stuff the weight of the vehicle has nothing to do with the subject.

I believe a 455 is less retrictive than a 302, so the benefit would be more. 5% would only be about 10 hp on a stocker (est at 210 hp) and wouldn't think that out of the ordinary. I will try to find data.

Gummi Bear · Apr 12, 2005

I dunno about power gains, I've not been impressed with the headers on my rig. I'm taking them off pretty soon. I'll send my manifolds off to Jet Hot, and go back with a stock like exhaust. I want the clearance, the simplicity and the low end torque that seems to be missing.

I don't care about speed, if I could make 300 foot pounds of torque at 1,000 RPM or less, I'd feel like I had the perfect motor.

The header / Exhast manifolds Debate

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