Shorty vs Full Length Headers

[1987cp]

Long tubes promote better scavenging of exhaust from the engine...and that's about as much as I can remember of exhaust/header theory 101.

Bingo, plus what Nate and Ivan said. I'm no engineer, but long-tubes are all about keeping port velocity high and (ideally) merging the tubes at a point where each high-pressure pulse coincides with low-pressure pulses from the other cylinders to further enhance the scavenging effect.

[Nathan in MI]

Here, this article covers it to a degree, along with a LOT of other exhaust stuff.

http://www.superchevy.com/technical/...t/0505phr_exh/

[Enigma]

I thought we couldn't use long tubes because of the whole steering shaft/box issue, and the column shift mechanism being in the way.?

[Pirate]

I thought we couldn't use long tubes because of the whole steering shaft/box issue, and the column shift mechanism being in the way.?

....exactly.

[Mr. Land Yacht]

well, yea...my headers were modded to fit around the stering shaft...and oddly enough, my uncle says they dont interfere at all with the column chifter linkage...when I pick it up, I'll be sure to take pics(when I finally get those in that is)

ok, so a related question...

how much better are the stock mustang shorties over stock manifolds?

and also, to that effect...how much better are 1 5/8" shorties and/or full lengths over those stock mustang shorties?

[1987cp]

well, yea...my headers were modded to fit around the stering shaft...and oddly enough, my uncle says they dont interfere at all with the column chifter linkage...when I pick it up, I'll be sure to take pics(when I finally get those in that is)

ok, so a related question...

how much better are the stock mustang shorties over stock manifolds?

and also, to that effect...how much better are 1 5/8" shorties and/or full lengths over those stock mustang shorties?

1) noteworthily

2) significantly, especially on a 7,000-rpm monster like you're putting in

[P72Ford]

I have always believed that the purpose in using long tube headers is to improve the torque (both the curve; usability, and the torque output itself). Pirate and Nate in MN hit the nail on the head. Pirate just used the technical term; scavenging. Scavenging is what helps evacuate the spent gases from the combustion chamber. The better the scavenging effect, the less the engine "works" to push the gases out. In fact, a system that scavenges well will not require any effort from the engine, gases will be pulled out simple by the design. With these thoughts in mind, one can see how better scavenging leads to improved torque and horsepower. I'm just getting into fluid mechanics now; we really haven't covered much relevant to exhaust flow (and nozzles and such) just yet. I'm not sure if it is correct to apply the Bernoulli equation to exhaust flow (anyone here know about that?). (There are certain instances where you can and can't apply it; I just never read that section of my book!).

MLY, if possible, you should definitely try to use those long tubes. For one, long tubes look cooler IMO. Also, its alot easier to swap your exhaust set up (no front pipes per se). However, the main reason I'd make every effoprt to use them is for their benefits. Since long tubes provide better scavenging, you are going to experience better performance with them. You are trying to squeeze all the usable power you can out of this beast; the long tubes could net you considerable gains.

That being said, I know where you're at. You want to jump in and spin wheels (which I would do plenty of). However, once the thrill dies down a little, you should definietly make an effort to get those on there. Make sure you don't butcher them either; butchered exhaust throws the scavenging to the wind.

Good luck, and keep us posted with picks when you get the car back.

[1987cp]

I'm not sure if it is correct to apply the Bernoulli equation to exhaust flow (anyone here know about that?). (There are certain instances where you can and can't apply it; I just never read that section of my book!).

I'm pretty sure it applies at least in part, but I think it'd be a bigger deal with stepped-diameter headers and the like, or maybe figuring how the transitions from 1-5/8" primaries (up to 8.3 square inches total cross-section per side) to the 3" collector (about 7 square inches) to the existing 2" mid-pipes (up to 3.14 square inches) will affect flow. Far more interesting theoretical fodder can be derived from applying waveform theory to the individual exhaust pulses, but that requires an awful lot of information such as pulse frequency, order in which the pulses arrive at the collector, nominal speed of the overall airstream (which I think would be analogous to the carrier wave?), and if you want to get fancy, even information about turbulent flow at the bends and also at the collector. But don't worry; I'm sure that fairly soon you'll even be able to give us a full and detailed explanation of the benefits of merge collectors!

[88Vic]

Also, don't longtubes give a deeper tone to the exhaust?

[Mr. Land Yacht]

I would think so..since they make it flow significantly better...

[DuceAnAHalf]

Also, don't longtubes give a deeper tone to the exhaust?

yes. my car with mid legnth headers, no cats true duals and one Flowmaster 40 (the other one was off the car at the time) was loud enough to hurt your ears at idle. there are some guys here who drive around with basically the same set up but with shorty headers.

[cld783]

hmm..I see...lemme give you a pic of my headers...I dont know if u've seen them...they're in the engine thread as well...

yup those would be your best bet. they are midlength

[DuceAnAHalf]

yup those would be your best bet. they are midlength

those are long tubes.

these are mid-legnth

[Mr. Land Yacht]

yea...what Duce has there is nearly the same headers...but his are mid..mine are actual ful length.
I doubt there would be much of any difference between his and mine as far as performance..maybe 5hp..I dunno.

[Archangel]

yea...what Duce has there is nearly the same headers...but his are mid..mine are actual ful length.
I doubt there would be much of any difference between his and mine as far as performance..maybe 5hp..I dunno.

So why are you dumping your full-length headers for a pair of crappy shorties? You already have one of them modified to clear the steering shaft and what not, why not have the other modified too?