C20 350 True Dual Exhaust - Glasspacks or Turbos?

[OneShot]

Hi all,

This didn't seem to fit very well in any of the subcategories in Engines and Performance, so I hope nobody will mind if I put it here.
I have a 79 C20 pickup with a new 350 and I want to replace the stock exhaust. I'm thinking true dual, cut the cat (no emissions test here), and do 3" aluminized pipe. Only thing is I am stuck on which muffler to get.
I want really good flow, like the glasspacks would give, but I don't want them too loud it's not fun to drive 70 miles. I'd like to keep my teeth in my skull! So should I go with glasspacks or the (slightly?) quieter turbo muffler? Will the turbo impede my flow that much?

Or should I consider a different exhaust setup? I'm always open to new ideas.

 

[rich weyand]

3" is too big for a 350 in a dual exhaust. You can't flow anywhere near that much with a normally aspirated engine. Run 2.25" duals. Bigger is not better, just more money.

A 2" H-pipe will help performance. Easy for the muffler shop to cut it in. Check this thread.
http://www.fullsizechevy.com/forum/general-discussion/classics/517289-new-exhaust-system.html

For mufflers, I am running Flowmaster 40s, which are a little loud, but not crazy. The Flowmaster 50s are quieter.

 

[MadOgre]

Really 2 inch will do the job quite nicely. Too big and you kill low end grunt. I put 2 1/2 inch duals and I noticed the drop in low end torque.

 

[OneShot]

3" is too big for a 350 in a dual exhaust. You can't flow anywhere near that much with a normally aspirated engine. Run 2.25" duals. Bigger is not better, just more money.

A 2" H-pipe will help performance. Easy for the muffler shop to cut it in. Check this thread.
http://www.fullsizechevy.com/forum/general-discussion/classics/517289-new-exhaust-system.html

For mufflers, I am running Flowmaster 40s, which are a little loud, but not crazy. The Flowmaster 50s are quieter.

I like that setup, and his truck looks almost identical to mine but with a lift. I like that he says it's quiet cruising but loud down low and has a good idle tone - that's pretty much what I'm looking for. Looks like he had it done right. What's the advantage of a balancing pipe? It just equalizes pressure when under load?

 

[SkinnyG]

A V8 does not split the combustion strokes left/right/left/right, but rather you end up with pairs within each bank firing next to each other. This can create odd paired pulses in the separate exhaust pipes. Adding an H or X pipe helps the extra pulses move to the not-currently-used-during-that-pulse other tube.

A bit more work, but better torque and sound.

I did 1-1/2" primary tube headers, into 2-1/2" pipe, an X pipe, the cheapest "turbo" mufflers I could buy, and 2-1/4" tails.

With my lumpy cam, it sounds healthy, but not obnoxious. Like a bouncer wearing a 3-piece suit.

You must be registered for see images attach

You must be registered for see images attach

No idea about torque before and after, as I never drove the truck before I started building it. It's fine as it is, but needs more gear.

 

[rich weyand]

What's the advantage of a balancing pipe? It just equalizes pressure when under load?

No. If you look at the firing order, it's 18436572, or LRRLRLLR. So when 4 exhausts, the pressure from 8 is still there, and when 7 fires, the pressure from 5 is still there. The balance pipe gives more space for the pressure from 8 and 5 in particular to go. If the firing order was LRLRLRLR, I don't think a balance pipe would help. There's no actual flow through there, the air in the balance pipe just moves back and forth.

Anyway, two ways to do it, an H-pipe and an X configuration. I believe the H-pipe helps torque more, the X configuration helps horsepower more.