Exhaust system for 383 stroker

[stringpickin]

Hello and good day.. Question, I appreciatte the responses. I have a 70 chevy 4x4 with a 383. I put a mild crane cam in it just above the torquer level for most custom cam setups for truck engines. I need a new exhaust system. I used the original 2" system for the last 7 years. I have been told that I should go to 2 1/4" pipe. I am concerned because I have always heard that with trucks if you loose the back pressure, you will lose torque.. Looking for user/or exhaust pro qualified input on this question.. Another place recomended that I go to a performance 2 1/4" dual to single muffler exhaust system with a 3 1/2" single exhaust to improve torque.. What do you think. Appreciatte your time.. thank you..

[72longbed]

Stringpickin,
In my opinion, the most critical area that affects torque, with regard to exhaust systems, is the first few feet outside the exhaust ports. For a 383 at that level of performance I would think a good pair of 1 5/8" i.d. tube full length headers to a 2 1/2" i.d. dual exhaust that has a cross over ( X pipe not H), around the end of the tranny. For best flow I would follow that X pipe with a true 2 1/2" dual exhaust out the back or wherever you choose to exit. Most performance exhaust pro's say when theres a question about header tube diameter " larger is not always better, and go with the smaller tube when you are in between sizes". Of course, the final application or intended use of the vehicle will play a part in determining header size. I.E. drag racing, circle track, street killer , or just daily cruiser

72

[MikeB]

Yep, 72longbed is right. Over-sized primary header tubes can hurt low speed torque. For a mild 383, 1-5/8" primaries are a good compromise between low speed torque and high speed hp.

From the collector on back, 2-1/2" pipes and mufflers are best. Larger won't hurt torque, but I doubt you'd notice any performance gains.

Heck, my mild 383 has DynoMax Chevelle shorty headers with 1-1/2" primaries, along with 2-1/4" exhausts and DynoMax Super Turbos. It pulls like a freight train off idle and revs to nearly 6000 rpm.

[stringpickin]

thankyou very much for your input. now to get the muffler people to listen to me.. lol....

[chevyhouse]

Agreed,for my 383 I run 1 1/2" primarys into 2 1/2" pipe with an x-pipe, also pulls ilke a freight train and I rev to about 6500-6800. In my opinion the X-pipe was the best part of the entire system, I ran with the same headers, 3" pipe and no X-pipe for a long time and the difference is like night and day. You can get an X-pipe from Summit for $30 but you have to ask on the phone.

Good Luck

[stringpickin]

Howdy again.. Okay, here is the scoop. Many years back I removed my header system and went to center dump manifolds.. Had my fill of headers after twenty some odd years of dealing with the heat, the continual loosening anc ets. I had hooker 1 5/8 id headers on my truck, but long short story, I got rid of them.. SO, that leads me to this point.. Do you think I should use 2" pipe to the mufflers and then go to 2 1/4 or 2 1/2 for the end pipe. Question about the X pipe.. Being that the X pipe is after the mufflers and the smaller tube at the dumps to the muffler, how could that affect torque.. thanks again..

[crazy longhorn]

with your stock manifolds, the restriction is 2".....I doubt that adding larger pipe at the rear will help perf, but will tend to make it louder. You can opt for a set of Vette centerdumps, to get to the 2 1/2" pipe size. A set of Dynomax Superturbos are a good deal for the bucks(good flowing, but not super loud). As far as the X pipe, they are better than the old H pipe......but will be d@mn hard to fit on your 4x4(I would stick with the H pipe). At the rear, you can cut the pipe size down a bit(if you like quiet), & you will be far enough from the heat that t wont hurt the flow. My 383 runs 1 5/8 tube Hookers, 2 1/2" pipe to the muffs, the H pipe is 2 1/4, & the tail pipes are 2 1/4(I tryed 3" tail pipes....loud as hell!) Like Mike said, the 383 pulls like stink right off the bottom, & runs to about 6000-6200......its running a 500 cfm Holley 2 brl, & a load of gear! Good luck,crazyL

[72longbed]

String,
You have misunderstood where the X pipe goes. Here's the layout from engine to rear of vehicle: 1. Exhaust manifolds or headers. 2. Dual 2 1/2" exhaust pipes. 3. The X pipe is next and within 3 to 4 feet of the rear of the engine!! 4. Again Dual 2 1/2" pipes into 2 1/2" inlet mufflers(2). 5. 2 1/2" outlets from mufflers to same size dual exhaust pipes to exit the vehicle where you choose. The X pipe should be BEFORE the mufflers and where the system gets hot enough to cook spray paint off of the exhaust pipes.

72

[crazy longhorn]

Originally posted by 72longbed
String,
You have misunderstood where the X pipe goes. Here's the layout from engine to rear of vehicle: 1. Exhaust manifolds or headers. 2. Dual 2 1/2" exhaust pipes. 3. The X pipe is next and within 3 to 4 feet of the rear of the engine!! 4. Again Dual 2 1/2" pipes into 2 1/2" inlet mufflers(2). 5. 2 1/2" outlets from mufflers to same size dual exhaust pipes to exit the vehicle where you choose. The X pipe should be BEFORE the mufflers and where the system gets hot enough to cook spray paint off of the exhaust pipes.

72

2nd that! not to be goofy, but I did exhaust work for a while.....on the 4x4, it will be tough to install an x pipe around the transfer case without stuff hanging quite a ways below the rails. Even the H pipe did not go in the optimum spot on the 4x4.....it fits better behind the transfercase.....crazyL

[stringpickin]

Yes, I did misunderstand on the x pipe. I do think it would be to much of a hassle to make that work before the mufflers.. thanks for all of your input.. Now I think I will keep it simple and go from 2" to 2 1/4 up front into some 2 1/4" pro-flows and 2 1/4' pipe from there to behind the tires.. Simple, clean,, and hey, doesn't my 383 make up for that 10 horseys I might be missing by spending a much bigger head ache making the H or X pipe work.. Thanks again guys. appreciatte it a lot.

[kickboxr3]

I sure am glad i ran into these post . I just pulled out my mild 350
sbc and will put in a very stout sbc 350 with trick flow head,air gap manifold ,crane cams,w/roller rockers and other goodies.
As stated earlier I would love to stick w/stock exhaust manifolds
but am afraid of losing all of the power i have worked for. Matching the exhaust with motor is not one of my strong points,any ideas or sugestion will surely help