my search efforts have yeilded that i sould run either a 2.25" or an 2.5" size exhaust tubing. heres the thousand dollar question. whats the best performance wise for a stock shortblock, milled head, with mild port work and a supersix carb and intake with a header? to me, the 2.5" seems a bit on the big size, but maybe im wrong here. a trick we do sometimes on our big block v8-cars is to run a bigger pipe to each muffler (3.5") then do a 3" tailpipe after the muffler. was wondering if its worth maybe doing 2.5" to the muffler then a 2.25" tail on the slant six? what can you guys tell me?

--chad

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74 swinger slant 6, the slowest, most fun car i have ever owned.

The number varies by what was used...

2.5" would be fine, especially since the tubing 'bender' restricts the pipe at every bend, thus reducing the pipe's internal dimension (I.D.) at every bend by about 1/4".... so you're back to 2.25" for the most part...

Super sixes and Feather Duster/Dart Lite's got the 2.25" pipe all the way to the muffler, then a 2" pipe out the back of the muffler to the bumper (roughly).

It may seem like much, but the exit hole in the exhaust manifold is only 1 7/8" - 2" at best, and if you open it up a bit, and open up the pipe a bit to make up for all the bends and restrictions to say 2.5" you'll get a nice growl depending on your muffler (kinda like the new cars do), and you may also pick up 1-2 mpg depending on your mill's build up and driving habits...(along with a little seat of the pants power)

-D.Idiot

That is exactly what I did! 2.5" from the header to the muffler then 2.25 from the muffler out ther rest of the way to the bumper. My sig says all of my other mods.

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70valiant' thanks, i think thats what i will be doing. how does it run? been to the track yet? we have basically i dentical setups it seems. i do my own exhaust systems, i just get a bunch of mandrel bends and straight pipe and hack and weld away. best part is that i can have a true pipe diameter and i can put the pipes exactley where i want to. i have done this many times for myself and friends cars and as with anything, practice makes perfect. i even squeezed a 4" single tailpipe through a mini-tubed and moved in leafspring a-body. but thats a story for another day.

--chad

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74 swinger slant 6, the slowest, most fun car i have ever owned.

I just put this engine work together in november. It runs good! In a space that I used to go 0-70 in I can now go 0-80. It will pick up some more once it warms up around here, I have the big heavy restrictive super six aircleaner routed through the flex pipe to the header on it which really reduces top end breathing. And I have a bad bog between 800-1100rpm. If I floor it it will just die. If I stand on the brake and rev her up to 1200, then let off of the brake and floor it at the same time there is this strange squealing sound and a bad smell coming off of the rear tires. That happens very infrequently consitering I'm running studded snow tires right now. The tracks up here open again in march I will be posting in the virtual drag strip once I've gotten out again.
If I had my own welder I would have tried to make the pipes my self also but I had Monroe Muffler Brake do mine. they got $160 for pipes, clamps, hangers, and labor. Between the head work, headers, pipes, the head, and all of the other little things it takes to swap heads and intakes I've got over a grand in the engine compartment. and none of them I really needed I just felt like having more fun getting from place to place.

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I'm very happy with my exhaust, it has a glasspack and sounds like a V-8 on acceleration. Many people feel glasspack make things too loud, but that's really only if you go overboard. I've heard that coating can also help an exhaust, I never really held much stock in that idea but I was wondering if anyone had experiences with it.

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My car may be slow to sixty, but at least it's been reliably slow to sixty for more than thirty years.

I used a 2.5 all the way and a dynomax muffler when I get done with my new motor it will be dual headers to a y pipe amd a 3 inch all the way back