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Here's one for you engine guys... I've got to fab up a set of headers for one of my projects with a Windsor. It will be aluminum heads, roller cam, 9.5 compression... Is it worth the extra effort to build some step headers and merge collectors? What part of the RPM range do the step headers have the most effect on, low, mid, or upper RPM's??? Can't find a lot on the net about them other then Jere Stahl trying to sell them!!!! Thanks for the input...
Here is what I have learned from David vizzard,
His opinion is that a 1 5/8 is good to about 375 hp ,then step up to 1 3/4.Short primary pipes favor top end power and long primary pipes favor the low end.He also states that equal leanth headers are of little use on a street ride and almost any engine for that matter ,based on the fact that each pipe comes into its own somewhere over the rpm band ,helping the overall power of the engine ,rather than one rpm area.
He also goes on to say that collector lenth and size play a much bigger role in making power than header configuration.A basic rule is that large short collectors favor top end and long small collectors favor the low end.A 2.5 inch collector is good up to about 375 and a 3 inch collector for 375 hp or more.He also states that a collector lenght of about 18 to 24 inches is best for the street,it can be made a little longer to help in the low end to get a heavy car under way faster.
Now this is where he stray from conventional wisdom:LOL: ,He says that in order to have a zero loss muffled system that you need a terminator/resonator box after the collectors .The size of this needs to be 8 times the volume of one cylinder or 11 to 15 times the volume of one cylinder is better.Then you need a muffler than conformes to his 2.2 cfm per hp rule .One of these per header and hes sayes exaust system losses are under 1 percent of what open headers dyno out at.Its also good to put a balance pipe connecting the collectors or second choice is to connect the termination boxes with a balance pipe.
This system is suppose to look like open headers to the engine ,making everything down stream of the terminator box invisible to the engine and the dyno sayes less than one percent loss with this system over open headers.
His take on the balance pipe is that there are 2 possible benifits ,increased power and decreased noise.It sayes that dyno testing has shown it to be 100 percent effective at noise reduction of about 1 to 3 db ,with 2 being the most common.Power is more tricky,about 60 percent of the engines responded with more hp ,with about 12 being the max and 5 to 8 hp being the norm.The other 40 percent of the engines the power was unchanged,but none of the engines lost power .Theres no down side to a balance pipe.
The size and length of the balance pipe are not that cruicial,2.5 to 2.75 are fine on the diameter,with anything over 2.75 showing no gains on engines under 600 hp.Dyno tests showed that pipe lengths of 18 to 72 inches dynoed out virtually the same.
He sums it up by saying,although he has not exsplained the theory behind everything discused here,you should be well enuff informed to build a near zero loss exaust system,as long as you dont loose sight of the essentials and principals involved,good results will be acheived.He also warns that if you step outside these recomendations you are on yer own.......:D
nice the short and sweet answer from just me is why not step headders dave it will not take much more work and the step tube is a over lap joint to the next size tube so there is abit less work. funny thing is i have never look at any thing from Dave V .so if i said that i have found out that equal headers almost never happen . the frame or front end parts get in the way .i had one customer drag s10 truck did run faster with a set of my custom long tube headers then his old hooker comp headers my tubes headder were not equal tubes so it has been proven to me at the track . there has been many set that i could never get them even .like chevy II with stock front ends with rise port bbc and many others i try to get it out of the head with nice flowing bends out of the the EX port and if you step the first step should be about 12 inch or so i have done some step tubes but do not have any thing to back them up. you would have to make two sets of headers the same but one step them dyno them out back to back .i think the power of the header is at the collector . the sad thing is i have built many sets and never seen any one try dif collectors but all of them big tube and step have work good enough not to play with them? just lucky
I doubt I'll be making two sets of headers for it!!!! One set is enough work!!!!:LOL: :LOL: :LOL: :LOL: Think I'll try them on this set... Maybe start at 1 5/8 then out 10 to 12 inches and up to 1 3/4 tubes. I do have a set of the 4 into 2 into 1 merge collectors with the final size being 3". Allegedly these will help scavenge the cylinders and pull a bit more bottom end power...or maybe they just help the bottom end power because of the longer length on the collectors????
As for the David Vizard stuff, I like the idea of a resonator in front of the muffler, just don't have room for it on this car. I have chassis dynoed before and after installing an H pipe... I did notice a decrease in sound level, and a small increase in mid range power.
Thanks for the input, more food for thought.
Dave S,
From what I have read, step headers will, in some cases be worth a few Hp - but not necessarily in a street driven car/engine. Stahl is not a big fan of them and this guy, the second listed, not sure of his credits, also does't feel that a step header is a real benefit - see #5. It makes sense to me.
I went to college with Jere Stahl - and he was developing interesting stuff w-a-a-a-y back then and was the class car geek.
http://www.stahlheaders.com/JpgFiles/issue3.pdf
http://www.x-pipe.com/Scavenge.html
Methinks(I know - archaic, but I'm an OF) that step headers need to be developed with a certain airflow - camshaft and head design and an RPM range that the engine will turn most of the time and that just welding up a set of pipes at arbitrary lengths without airflow/dyno tests wont do it and that Hp might suffer:whacked: :3dSMILE:
If you do build them, please make sure that you keep the forum updated as I hope you can prove these guys wrong:D .
Some very interesting reading on Stahl's site, seems the other guy was just pedaling some new gimmick... Guess I'll go with Stahl's suggestions, he sure does seem to know his way around an engine, especially the exhaust side of it!!! The items on velocity are certainly true, can't argue with basic science!!!!! Gentle bends (didn't that used to be a TV show) and properly sized tubes and collector's still seem to be the best answer to cleaning out the exhaust. Maybe I was just hoping for a magic bullet!!!!!!! :LOL: :LOL: :LOL:Quote:
Originally Posted by Irelands child
Quote:
Originally Posted by Dave Severson
Dave S.
We've (almost) agreed on something - finally:cool: !!!!!!!
Probably was a TV show - I just have never been addicted to the 1 eyed monster(except for car races). My wife is regularly saying "Isn't that (a name) from the TV show (a name)". My standard answer is that I was too busy earning a living in some faraway land to have watched that drivel.
Stahl headers have always seemed to be the Cadillac (now Lexus?:CRY: ) in headers and he has been doing them for a long time for a lot of the 'name' racers, so his credibility, to me, is way up there.
Dang, I just realized that!!!! I must be getting soft, heck it was 3 years before Uncle Bob and I ever agreed on anything!!!!!!!!!!!:LOL: :LOL: :LOL: :LOL:Quote:
Originally Posted by Irelands child
Gotta go do a little work, then it's off to another Friday afternoon at my favorite junkyard!!!!
I do recall a few of the spears that you and Uncle Bob lobbed back and forth - maybe I'm more quietly opinionated:LOL:Quote:
Originally Posted by Dave Severson
Happy pickin's - my big thing today is the lawn(about finished) and find some good 500 wet & dry to final sand so maybe, just possibly, I can put some color on some of my project parts next week.
Friday early disappearances are called POETS = (P*$$ Off Early Tomorrow's Saturday)
Methinks(I know - archaic, but I'm an OF) that step headers need to be developed with a certain airflow - camshaft and head design and an RPM range that the engine will turn most of the time and that just welding up a set of pipes at arbitrary lengths without airflow/dyno tests wont do it and that Hp might suffer:whacked: :3dSMILE:
If you do build them, please make sure that you keep the forum updated as I hope you can prove these guys wrong:D .[/QUOTE] well air flow and length has alot to do with any set of headders and heat get out of the tubing is power to more heat going out the tube and not threw it and how long has alot alot to do with were the engine is and where the tube needs to exit some times they get abit longer am i jerry stall NO but i build alot of headers and jerry is not me i do ok :LOL: shame less plug why not. i did build a set of step headders on here and posted all of it :confused: well ok i am not jerry S or david V:LOL:
That was gonna be my suggestion Pat. Just get a compressor & push the air through the engine. :LOL: :LOL:
My theory is big exhaust & force the air through. :whacked:
you are a very smart man:3dSMILE:Quote:
Originally Posted by pro70z28
Thanks Pat. Check is in the mail. :LOL: :LOL: :LOL:
I topped 'em off with 4" collectors:whacked:
that looks good i would show you mine but.. some one may be looking there is a city bus missing the EX :LOL:Quote:
Originally Posted by pro70z28