I have poured over all the exhaust sizing threads I could find on the HAMB and have played around with my exhaust many times in search of that perfect "tune". Here's what I have right now... 250 Chevy Inline 6. Split stock manifold. 1 3/4" pipe. 2 Brockman's 17" body/24" overall steel packs. Run all the way to the back, exiting through 2" pencil tips. I originally ran it with one straight pipe and one steel pack, but my Chevy is a daily driver and the straight pipe started to make me crazy, AND deaf when on the freeway. Now with two steel packs the decibels are manageable, but it doesn't have the same character. My plan is to neck the tubing down about the last three feet of exhaust. I'm thinking of using 1 1/2" or 1 3/8" tubing for the final run to the new 1 1/2" pencil tips I bought just to give it a slightly higher pitch. Right now it's a little too throaty. In all the threads I checked out, nobody mentions using 1 3/8" pipe. Question: Is 1 3/8" tubing excessively small? Do you think there will be much of a sound difference between the 1 1/2" and 1 3/8"? My rolling project. Thanks, Jason
1 3/8" exhaust pipe does not exist. 1 1/2, 1 3/4 and 1 7/8 are the smaller sizes for exhaust tubing. You won't find it because it is not made. If you find something that small you won't find elbows or a bender to do anything with the pipe.
I did see 1 3/8" and 1 1/4" SS exhaust tubing made by Patriot and listed at JEG's, but was also thinking about using regular steel tubing I found at a metal supplier locally. They have something that's 1 7/16" OD, 20 g, with a 1 3/8" ID. Didn't think about the bender availability though. Also, I assumed that early Japanese cars like Datsun's and Toyota's must have run pretty small diameter exhaust tubing too.
Smaller diameter equals higher gas velocities equals higher pressure drop equals less power and worse mileage. Use 2" and get a decent muffler if you're concerned about it being too loud, you will get a little more power. Costwise - forget it, you won't save anything by going smaller diameter. My $0.02 anyway. Good luck - by the way, your car looks good.
Thanks. Not thinking economy or performance really. The two steel packs offer plenty sound managment. Just looking for the perfect "6" sound. A little rap and pop. Hoping one of you Bomb guys will know.
Yeah sorry, when I wrote, "in search of the perfect tune" I was talking about musical tune. Had to clarify. Not trying to performance tune the car, I'm just trying to get the sound out the pipes right. Thanks.
Once you install mufflers, even short ones, the sound changes, as you remove a lot of it. Smaller diameter tailpipes will give you a thinner, brighter version of what's left. No exhaust with any style of mufflers will sound anything like straight pipes of any diameter or length, especially with chevy 6s - even later ones that flow better and more quiet at higher rpm.
I actually have a single shorter (12") steel pack that I'm going to start with on one side to see how the sound changes.
I have not run the smaller tubing, and am planning to do exhaust on my 64 c10 with a 292 starting tomorrow. I'm going to be running 2 1/4" out of the split headers immediately in to 2" inlet-outlet 30" long Cherry bombs, and then 2" the rest of the way out. I've heard it said that the split 6 manifold guys like the 1 7/8" for the cackle and rap on tip out. I'm not aiming for all that. As for dies for 1 3/8", my Ben Pearson MC58 machine has a set of 4" radius with long, and short shoes, so, yes they do exist.
Thanks for that info bodi. I welded in the shorter 12" steel pack I had, so now it's 17" on one side and 12" on the other and still running through 1.75" tubing all the way out back. Now I've got a good balance between two worlds. It still raps and pops like it did with one straight pipe on one side, but toned down a good amount. Not as harsh on the freeway! Still considering using 1.5" tubing for the last couple of feet of exhaust.
Good to hear you are happy with your results. Any guesstimate how close your mufflers are to the actual head? I staggered my Cherry Bombs as I had read that doing so would make each bank sound different giving a better split manifold sound. I had read that the further forward you had the muffler, the more cackle and pop you would get. That holds true on my rig. My driver's side muffler is about 36" away from the exhaust valves, and it cackles like crazy. The other side is nearly twice the distance, and is pretty subdued. I think some of the cackle may be coming from my exhaust/intake gaskets not sealing properly. Have to do more research on a possible better gasket. Sure is fun stuff to play with!
Yessir, been having fun changing my exhaust system for the last five years! Like tuning an instrument. I staggered my steel packs too. The longer one is closer to the manifold. Probably about 36" as well. The shorter one is only about 6"s further back. They sit right about under where my feet sit. I did experience more snap, crackle, pop when there was an exhaust leak. I think the added O2 did something to the mixture or the way the unspent gasses burned off in the tubing. I have had really good experience with the "thick gasket" I got from Cliffords Performance. Seals and conforms well to both surfaces. With wanting to change the last few feet of tubing, my goal is to change the tone. Right now I'm happy with the amount of rap and decibels it's putting out. Just like musical instruments I want to change the diameter of the tubing so I can go from a Trombone to a Trumpet. Just a slightly higher pitch and crisper sound.
The Jalopy Journal
