ok I was talking with the welding instructor at school (who is the smartest person I know) and I mentioned that I'd like to get headers for my car and he said that its pretty much pointless unless you are running 450hp+. he started talking about the flow requirements of a 350 and how the stock manifolds are enough. my question is can anyone show me the math to prove him wrong? or maybe a dyno sheet showing the difference between headers and no headers.

the only reason I did't call on him right away is he could teach a fluid dynamics class and he is literally a genius.

For a genious he isnt too bright....

They don't usually teach you fluid dynamics when you learn to become a welder. He is wrong.

lets ignore the fact that he welds, which is a part of his business which is fabrication/repair/anything else. thats after turning wrenches on gas and diesel equipment for 20+ years (and talking having degrees in fluid dynamics, metallugy (sp?)and who knows what else). basically I have no doubt that he knows what he is talking about, which is why I would like something that shows beyond a doubt that headers are benifical (sp?) regardless

Maybe the fact that people from california to over here in florida, and up through canada somehow manage to pull lower 1/4 times after the installation of headers.

As I said, he's a moron, or f'n with you.

Just because he's a "genius" doesn't mean he's a "Car guy"...I mean PERFORMANCE....


I still remember my first Auto shop teacher telling me how it was pointless installing headers, cam, etc in my old Chevelle, as the gains wouldn't be noticeable. LOL

I have no doubt that headers are good, but before I tell him that he is wrong I would like to have my facts straight

Just tell him that parts places are rittled with exhaust products that reduce ET's. There wouldn't be companies like Hooker, flowmaster, borla ect ect if their stuff didn't improve over stock OEM junk. I am sure his fluid mechanics exposure was minimal at best. Just be simple with him. Ask him if he would rather run a marathon breathing out of a straw or a toilet paper tube.

ok.. so your try to tell me that... the stock manifolds breath just as good as header and are no need...... HA HA AH AHHA HAHA AHAHA AHA HA AH AH AH...... thats funny cause you ussally make power by making the motor breath.. and by letting the exahust get out easy and fast it make the motor work less to get it out which free's up the HP thats like saying i'm going forma 1 bbl carb to a 4 bbl and wont see any diffence in anything... *** what a moron.. and if he says it is like that tell him to prove it and bring back the evednece to us

shifty: now thats a good way to put it

everyone: he also said that the stock exaust on new cars flows better than headers...thoughts?

he also said that headers also slow down the velocity of the air and reduce scavaging

... OEM flow better.... scince when

The larger the pipe the more the flow. Why do you think fire hydrants have 2 different size openings? There is a point where going too big hurts scavaging. However, headers are desinged not to exceed that per their intended application.

it's true somewhat. In 98-02 F-bodies, the stock manifolds are just as good as headers, if not better... some people have put headers on them and actually lost power. Now that's only one example of it... he cant honestly sum up ALL MANIFOLDS as being as good as headers by a couple examples.

SIMPLE WAY TO LOOK AT THIS


you don't need headers till your running 450hp right?
so lets see
you don't need heads prolly till your pushing at least 400hp
and forget about the came since that isn't needed till around 350hp or so
and the itnake isn't needed till around 800hp
gears don't do you any good till around 1200hp prolly
boring the block isn't neeed till you make at least 500hp I would say
pistons eh not good till around 600hp


see a common trend here with what he said?


if we followed his advice on not doing something cause it isn't needed till you hit such amoutn of horsepower then we dont' get anywhere


where if we do little pieces here and there we will be able achieve our goals

they woud slow down the exhuast if you went from a 1 3/8 inch pipe to a 1 3/4 inch pipe
then yes it would reduce scavenging

but if you went from as tock size manifold to a stock size header the header will be a lot more smooth flowing with a little less turbulance or interferance from one pipe to the other

and wha the stock maniofolds are loggers aren't they?
about the worst design you can get due to all the turbulance and pulse timing issues with almost NO scavenging effect

I gained 20 hp by getting Edelbrock headers and a high flow cat this is before and after with no other mods done at the same time.

After you take off iron exhaust manifolds give them to your teacher as a chrismas present every good teacher allways needs a paper weight.

Once you take a look at the exhaust manifolds you will laugh at how GM let anything so poorly engineered leave their factory.

simple.

take a bendy straw and have it straight... point out the air goes thru easily.

now hold it flat, cut 4 windows into the side of the straw, and tape off one end.

obviously, its harder to blow thru. the air has to make a immediate right turn.

nows the fun part. put 4 bendy straws together with big radious bends.. like a header. point out that since they all arnt going into a immediate shared channel you can vari the length to tune it so that one pipes exhaust wave can help scavenge the next cyl.

and the larger radius turns help it flow better.
and with modern thermal coatings, it holds heat better for greater exhaust speed

and you have more flow for when you exceed the abilitys of a factory system...


plus, point out that the formulas hes using does not take into account the friction of the air, bends in the system.
and point out that the air doesnt FLOW thru.. it pulses.....




that ought to get ya started.

Once again, it comes down to "the package".

You have a 350 TBI? What heads are on it? If swirlports, then large headers, say 2" primaries for the sake of arguement & overkill, would definitely slow down exhaust flow velocity to the point that those small sodastraw ports would be overwhelmed - low-end torque would be absolutely killed, and the engine would never be able to rev high enough to get the exhaust flow velocity up to the point where it would begin the "scavaging" effect.

However, 1-1/2" primary headers would work very well on such an engine. But, again, it's not one single part that determines the final outcome. If you still have the 2-1/4" TBI exhaust on the car, that will choke off flow and negate most of the benefits of the headers.

And, as usual, the total is not the sum of the parts. If you put on an induction system that should boost the power by 50 HP, but the exhaust holds it back, you won't get the 50 HP increase. By the same token, if you put on an exhaust system that would increase your power by 20 HP with the stock induction, doing both would not increase power by 70 HP, because the 50 HP assumed proper exhaust. Getting a total package of induction, cam, heads, and exhaust may double the power, however, but only when all the parts are properly matched and done together.

Most of the time, headers will increase power over a factory cast iron manifold system. It all needs to be matched to complement the entire power train system, that's all.

How to disprove this apparent MENSA card carrying member?

It's called a dynamometer.

dy·na·mom·e·ter
Pronunciation: "dI-n&-'mä-m&-t&r
Function: noun
Etymology: French dynamomètre, from Greek dynamis power + French -mètre -meter
1 : an instrument for measuring mechanical force
2 : an apparatus for measuring mechanical power (as of an engine)


You can then proceed to tell him that when this apparatus shows an increase from one part or another, it is generally accepted that said part swap indeed increases the power output of the test subject.

As this has been the case countless times after the installation of headers, I think I would want him to prove to me that headers would indeed be worthless.

We won't get into fluid dynamics, acoustics et al. No need.

Well the most obvious thing I can think of to throw into this is that an exhaust manifold has right angles in it, and a header has smooth bends. Im sure if you explained this to "captian fluid dynamics" he would figure out pretty fast why headers rule and exhause manifolds are garbage.

Now that is true to a point. A mag did an article recently on this. When using a 15/8 header they saw no flow diff. but when they stepped up to a 17/8 header they started to see increases.

anyway I appreciate the input from everyone. I'm looking forward to seeing the instructor again so I can tell him most of this.

five7kid, yep its a 350tbi from a 89 half ton p/u; the engine is in need of an overhauld and some various new parts (including heads).

rx7, I hve to say you make your point very well, I'll have to mention somthing along those lines.

when my car was stock and i put on 1.5" primary dynomax shorties i went from 15.1 @ 93.25 to 14.6 and quicker at 95.5mph (same weather) in the fall in 35* air i hit 13.9 @ 97.

there was definitly a big improvement when i changed over to headers and they were the ****tiest headers and y pipe u could get for our cars.

Headers flow more than manifolds. More flow = more hp. Theres your math