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iTrader: (1)

I'll get to the point: I'm running a stock 5.3 with a mild cam, and the car is known for fitment issues with certain long tubes when doing an LSx swap. I want to take the easy way out and get a mid-length header. I'm thinking 1 5/8 with 2.5" collector. Peak HP probably just under 6000 RPM

In my mind, the less the exhaust (on a small motor) is allowed to expand early-on, the better..(?) If I put 1 3/4 longtubes on it, I would think the exhaust gas would be able to expend somewhat, just to then run into the pressure areas such as mufflers, etc. Where the smaller tubes into the smaller collector would seem to allow less expansion.. Or does that matter at all?

My only problem with shorty and mid length is that they are not tuned-length. And that tuned-length stuff makes A LOT of sense to me.

BTW, most LS1 camaro headers fit on this car, sort of

Nereus

Other than the fact that the exhaust tuning adds minimal power to the engine compared to intake tuning, and I am assuming the car you are referring to was made in the 70's, older cars (pre-EGR) have a simplistic view of exhaust gases in a similar fashion as sewage. It is not useful, and should be dumped. When EGR came along (80's and 90's mainly) the exhaust diverted part of the flow back into the cylinder during lower rpm, this reduces the viewed combustion volume of the power cycle, thus you can get less power using less fuel while still using all of the volume. This is advantageous at low engine demands. New cars use Helmholtz resonance in the exhaust to actually SUCK the exhaust out of the cylinder, but must be tuned to each engine spec.

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iTrader: (1)

^
5.3 LsX engine swap into a 78 G-body = Gen 4 Camaro headers.
Question: Can a set of shorty 1 5/8 headers do the trick, or are 1 3/4 long tubes the only way to go?

I'm looking for 1500-5600 RPM TORQUE

Nereus

Well, since your car is reasonably old and probably didn't have new tech (expensive car, don't think pontiac makes those), it probably treats the exhaust as waste, so larger diameter is going to decrease back pressure in the system meaning your engine will breathe easier. But I must reiterate, the power you will be getting from this (power being one derivative from torque) is minimal especially compared to cost added. And at those rpm, the flow of exhaust gases is probably not enough to warrant larger headers. I am not an expert in exhaust, but I know very well how the dynamics work. I would put my money on whichever is cheaper, because honestly the power difference between the two is tiny.

Keep in mind the resonance I was originally talking about is more beneficial at high rpm, these exhaust systems are tuned I'm assuming, meaning they take advantage of this phenomena; at low rpm they do almost nothing.

NoShow

iTrader: (1)

ONE MORE TIME: LSX SWAP! (THIS IS LS1Tech!) The entire pontiac driveline and exhaust is going to the scrapyard!

At least I'm getting some response though >*crickets*<

OutlawDrifter

iTrader: (9)

noshow...i'm kind of in the same boat with my swap right now. trying to decide if mid-tubes are worth their savings over long tubes. i think the thing to remember with the 5.3l is it flows lots and lots of air compared to the older gm engines. (my build consists of a 6.0l base)

long tubes will definitely make the bigger torque numbers, but i don't think that number will be huge over the mid-tubes. hp should be close to the same for either setup. BRP has conversion headers for g-bodies, not sure if you have looked into them or not yet. hedmans husler side actually makes them, and offers quite a few variations.

also consider how you will be using this car, racing, or mainly a cruiser.

hopefully the mad scientist above won't have any comments about this....haha