Am I losing alot of power with shorties and a single exhaust? My motor is supposed to make 412 hp with long tubes and duals in chevy high performance, it also dyno's at 412hp on DDyno 2000 with small tube headers and mufflers. Can anyone tell me what kind of power I'm losing? Is it worth going to full tubes and duals or just full tubes and slp loudmouth?

 

...or a cutout on my current exhaust where the cat used to be?

 

You aren't loosing much. To me it would not be worth it to change, especially with all the drawbacks to longtubes. A cutout wouldn't hurt though.

 

dyno 2000 is notoriously inaccurate....

but in any case, it shouldn't be too restrictive....at that power level, depending on flow specs for the heads the single 3" might be a bigger problem.

shortie headers dont necessarily lose any flow over a full header....they just dont have the collector to promote better exhaust scavenging.

the scavengine ability of a full header is usually worth a good amount of low end torque on an engine making that much power

 

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At a stock engine I would go with shorties, unless you plan on dropping some serious muscle in there later.

 

it depends......but you will almost always see much better numbers from a full length header, due to their excellent scavenging ability

 

judging by my car, i'd say you can make pretty good power with shorties. I didnt note what kind you had but I think edelvrocks are about the worst, and i still went over 118 mph. Ohh, and for reference, i have a cutout where my cat used to be and I barely get a tenth from it. But cars like buckeyeroc's did pick up more.

I'd say keep the headers you have.

 

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i see absolutely no noticeable difference in ET or trap speed when i run my exhaust open...must flow better than i thought it did

 

Read the latest issue of Car Craft. Great article on headers. Shorties make more peak HP, LTs make more low end torque.

 

just so you know, thats absolutely not the truth in all cases.....for that specific engine combination it might be true, but overall its not.

ever see a sportsman racer with shorties on it? nope and you wont, cause shortie headers are built as a compromise, to make things easier to fit and install, not to make maximum power

full length headers are full length for a reason.

the torque is created by the equal length of the primaries and the design of the collector to provide superior scavenging

peak HP is achieved by a combination of things, one of which is maximum flow, and maximum velocity.

maximum top end power can be obtained with zoomies, but you wont find those on a street car anytime soon

I read that article, there are alot of explanations for the results that they obtained, engines work as a system and not having a the intake, cam and exhaust matched well could cause variations similar to that.

But remember racing happens on the track not on the dyno.....
next time your out racing, count how many race cars have shortie headers....theres a reason for it, its not a mistake.

i love car craft....but taking their word as gospel is like accepting everything that you read in motor trend at face value

 

383backinblack - I was citing an example that on the given engine, a very typical SBC buildup <--- which is the key here, that shorty headers made more peak power than the full length. That's with the same primary and collector diameter. Is that the case on every single engine combo ever? Who knows. I don't care.

Comparing a 1 5/8" shorty with 2.5" collectors to a 1 3/4" or 1 7/8" full length with 3" or larger connectors is foolish. Of course if you build an engine to utilize the larger exhaust it will perform better with the latter. If someone built a comparable size shorty things would a little more fair. But no one does due to the intent of shorties which you already highlighted. You don't see them because no one produces them.

All I see is a typical SBC buildup making more power with shorties than full length. I don't take mags as gospel, but rather as a guide. They have money to experiment when I do not. Why not learn from someone else's trial and error? I've learned just as much from others as I have personal experience. I have a subscription to Car Craft for the same reason you do...

 

i wasnt trying to bust your ***** man.....i just wanted to explain the issue a little because you just said flat out that shorties make more peak power than full length headers....

i understood what you were talkin about, but keep in mind that there are alot of people around here that are just starting to learn things about cars and engines......so if you say something like that, someone might just assume that what you said is the final word.....

just trying to be considerate of other people that dont have quite as much experience, because you never know whose reading this stuff

 

Agreed. And that is why I am making my point Most around here claim that full lengths always make more power than shorties. I wanted to point out that's not always the case. I've got a good friend who spent nearly $1000 going from SLP shorties to Hooker Super Comps only to run the same ET and lose 1 MPH on a low 12 second car. Tuning didn't help.