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shorty headers vs full length

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shorty headers vs full length

Postby tod85 » Thu Jul 31, 2008 12:41 pm

I know youve built and dynoed a million motors at one time or another, thus maybe you give me some simple insight in regards to a discussion on another board.

On a fairly mild street/strip 400-500 hp sbc, how much, if any, will shorty headers lose in HP/TQ vs full length headers ?

Same question, but this time a well warmed over 600-700 HP 406 sbc ?

Thank you
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headers

Postby bigjoe1 » Thu Jul 31, 2008 3:32 pm

In the testing I have seen, the shorty headers will make good top end HP, but you will loose some bottom end. On most race setups, power below 5000 or 6000 in not that important anyhow. The whole equal length thing is mostly about more low and mid range torque. On a 500 HP engine, the shortys lost about 25 lbs at max torque and the top end was the same.

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Postby RW TECH » Thu Jul 31, 2008 3:48 pm

I saw a little more loss than that on a 302 Ford, but it was basically the same deal where above peak TQ RPM the shorties were "OK" compared to full length but at & below peak TQ the engine was down a ton. Seems like about 45 ft. lbs. at around 4K RPM.
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Postby tod85 » Thu Jul 31, 2008 4:11 pm

Thank you both for your replying !!
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Postby n2omike » Thu Jul 31, 2008 6:08 pm

You have to be careful when defining 'shorty headers'.

The units sold as 'replacements' for the factory units that bolt right to the original exhaust system generally have small ball/socket connectors, no collectors, and lose a lot of power across the board.

Short-Mid length standard design headers with a real collector aren't outright restrictive like the units designed to replace stock manifolds, and are what I believe BigJoe is talking about.

Good Luck!
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Postby bigjoe1 » Thu Jul 31, 2008 6:15 pm

The ones I saw were short, but they had a regular three inch collector on them. I have never tested the ones that replace stock manifolds.I dont know what the ball connecter thing is all about either.

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Postby tod85 » Thu Jul 31, 2008 7:19 pm

To tell you the truth, besides the occasional street car I've never even seen shorty headers on a motor.... I run full length supercomps....thus, I really don't know much about shortys and really don't know why anybody would run them unless maybe its a sound thing I guess.

But, we were having a discussion on another board and somebody was stating that they are basically equal in power to full length headers.... the problem is, there really isn't any data to back that up..... very few, if any do before and after tests with shorty's vs full length headers or at least none that are published that I am aware of. But, I thought I would ask somebody that I know has built and dynoed a lot of motors and I knew Mr. Sherman posted here.... so I asked. If anybody else has any insight on this, I'd be interested in hearing it.
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Postby 1989TransAm » Thu Jul 31, 2008 7:53 pm

I personally think it will come down to the basic design of the shorty headers. There are a wide variety of them out there. Heck I have seen them mixed with 1 1/2 inch and 1 5/8 inch primary tubes on the same header.

I think if you have a quality shorty header with the proper primary diameter and proper collector diameter the results are going to be what Joe and RW have reported. By the same token there are some shakey long tube headers out there with mixed primary lengths that kind of defeat the purpose.

I think you have to qualify that each style is a proper matched to the motor.
Last edited by 1989TransAm on Thu Jul 31, 2008 8:15 pm, edited 1 time in total.
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Postby bigjoe1 » Thu Jul 31, 2008 8:10 pm

I always like to sture the pot. Way back when I was at Edelbrock. We were testing a bunch of headers. We ran about ten differant sets and came to the conclution that the equal lenght made the best all around power. Almost all the headers we tested the primary pipes varied in length by about 15 inches. We had a set built with 2 pipes at 32 inches and the other 2 on that side wewre only 16 inches long. This miss matched set made the most horsepower and the same as the best torque. SO MUCH FOR EQUAL LENGTH

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Postby Ron Golden » Thu Jul 31, 2008 10:16 pm

If you do a search for "David Vizard" I think you'll find he did some testing on header length. Like Joe said, primary length isn't that critical unless your tuning for a narrow rpm range.

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Re: headers

Postby RW TECH » Fri Aug 01, 2008 2:54 pm

bigjoe1 wrote:I always like to sture the pot. Way back when I was at Edelbrock. We were testing a bunch of headers. We ran about ten differant sets and came to the conclution that the equal lenght made the best all around power. Almost all the headers we tested the primary pipes varied in length by about 15 inches. We had a set built with 2 pipes at 32 inches and the other 2 on that side wewre only 16 inches long. This miss matched set made the most horsepower and the same as the best torque. SO MUCH FOR EQUAL LENGTH

JOE SHERMAN RACING ENGINES


Similar story, where an "up north" NASCAR team owner insisted that his headers were a science project. All primaries, steps, etc. identical in length to eachother.

They borrowed some simple 1-piece headers from a competitor that DID NOT have equal lengths but were built to MINIMIZE THE NUMBER OF BENDS in each pipe. Beyond that, the step lengths were staggered a bit to compensate for the differences in overall primary length from one pipe to another.

The ones that had fewer bends and all pipes at different lengths made a significant amount more power and by far were easier to build.
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shorty headers

Postby bigjoe1 » Fri Aug 01, 2008 8:44 pm

A funny thing is going to happen. I have a 360 Mopar ( 408 stroker) ready to run on the dyno, and I am going to have to use some shorty headers because, the normal car headers will not fit on the dyno. The customer has some old shorty headers that he is going to bring over so I can make sure they will clear everything. I will let you all know how this turns out.

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Postby 1989TransAm » Fri Aug 01, 2008 9:59 pm

Thanks Joe, looking forward to the results.
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Postby 67RS502 » Fri Aug 08, 2008 7:35 am

I would also be interested in the results Joe, if youre going to dyno with shorties and full length.

I had a Luv with a 383 that I ran some old junky 1 5/8" shorty (block hugger) headers which I port
matched. They were like the old ram horn manifolds as they all came together about 6" below the
center two cylinders. They had 2 1/2" 3-bolt collectors, after which I ran 3" pipes with an X-pipe, then
necked down to 2 1/2" Dynomax turbo mufflers. The 383 made 483hp/495tq with some nice 1 3/4"
dyno headers. But I used the junky 1 5/8" block huggers that came in the Luv truck when I got it.
It ran decent with the shorties, 11.30s @ 122. Then I bought the Hooker Super Comp 1 3/4" full
length headers, stuck them in (with the same exhaust) and went back to... unfortunately something
was wrong with my Luv, it just ran like crap, and I couldnt figure out what was wrong with it,
it just felt like it was down on power everywhere. It was NOT the full length headers, because
it had run great with then on the street before. The only thing I found was a possible vacuum leak,
and to this day I dont know what was wrong with it, and more importantly how much the full length headers
would have been worth at the track. I will say this, it felt like it had a bunch more (30-40?) tq from
around 3000-5000 above that it was about the same power wise. But the thing to consider is the shorties
were 1 5/8" dia. and 6-9" long, and the full length were 1 3/4" (which is what the engine really needed I believe)
with 32" long primaries. So the shrties may have been on the small side diameter wise which may have helped
with tq a bit, but the primary length was way too short for power below 6500rpm, which should have been around
32" for that low a rpm band.
Now I'm in a similar dilemma, I just picked up a nice street Vega which looks really tight and shortie headers
would be so much easier then the 1 3/4" Hooker super comps which they make for it. So I need to figure out if
its worth the hassle to do the full length Hookers or just get some shorties for it and be done with it...
the same 383 is going in the Vega.
Thanks for any input.
67 camaro
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420 - 641hp BretBauerCam, 1.39, 9.79 @ 137.5
383 - 490hp 224/224, 1.56, 10.77 @ 124.6
502 - 626hp 252/263, 049s 1.44, 10.08 @ 132.7
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headers

Postby bigjoe1 » Fri Aug 08, 2008 9:52 am

The guy brought the shorty headers by and they were SOOO bad I told him it will kill the performance of his engine. I am going to find another way to test his engine. I have not figured that out yey. SORRY

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