3 inch exhaust

[1969Chev]

Anyone running 3 inch exhaust coming out before the rear tires? I'm getting my exhaust done on Wednesday and that's how I am getting it. Anyone have any input or any pics?
Thanks!

[Lees68GMC]

2-1/2" with 4" stainless tips. Cheap $39.00 each Thrush (Flow-master rip-offs) sounds quiet, low rumble at idle, sounds great under power, no annoying cruise drone either. YES a quality X-pipe is superior, but couldn't fit one without possibly cooking the front u-joint and facing crazy bend issues, This simply balances the cylinder banks and still sounds damn good, again cheap versus $100.00 X-pipe too.

My opinion, I'm an old fart ex-racer, and can tell you 2-1/2 is good for up to 600 HP and any flow advantage with 3" is seen at high RPMs, so doesn't make sense to me to design for 5% of time performance in a street truck, in limited space but, to each his own, eh?

My Two Cents, hope it helps

[RustyBucket]

Lees68GMC, nice clean installation... are you the welder?

[Lees68GMC]

I wish, no local friend did it, I just said how and where I wanted it run.

[72MARIO]

I had my truck like that for a few months......dual 3" with super 40's. then I added the H pipe.....then tail pipes out the back made it better but it was still draining to drive. I couldn't take the noise. I am not a old guy either. depends how often/far you plan on taking the truck out.

[72MARIO]

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[Tillik]

Subscribed. Had similar question

[piecesparts]

I agree with the comment about the capacity of the 2 1/2" piping. The 3" piping may and in many cases will provide a loss of efficiency in the exhaust system. The larger tubing will provide for a loss of scavenging effect on the engine and in the long run, cost you horsepower and possibly fuel economy. The removal of exhaust is important, all the way back to the intake process, since the removal creates the vacuum that really pulls the new fuel laden air into the cylinder. If the exhaust gases are allowed to travel lazily out the rear, then the pulling effect is lost. The right size piping will allow the exhaust to cool and collapse the full length of the piping giving that vacuum effect and not a reversionary effect that will cause the engine to perform poorly.

Looking great is not always the right answer. I spent a lot of time on a phone, talking to engineers for Flowmaster and Magnaflow, when I built my exhaust for my GMC.

[kwmech]

A single 3'' pipe behind the rear wheels will flow anything you can throw at it, unless you're putting in a big block with a blower that's gonna spin above 6k

[trac209]

Originally Posted by kwmech

A single 3'' pipe behind the rear wheels will flow anything you can throw at it, unless you're putting in a big block with a blower that's gonna spin above 6k

Exactly,I know guys who run well into the 450hp range with a single 3 inch system. 2.5 is plenty in dual form.

[cdowns]

3" exhaust is the hot tip for makin noise and not goin anywhere fast

[volksworld]

had mine in front of the wheels with a shortbed and a sliding rear window (no A/C )....after 2 hrs of driving the fumes would damn near kill me

[Dave67]

Question for Lees68GMC. I noticed you ran your exhaust through the trailing arm cross member. My LWB C-20 has a brace on each side of the X-member going to the frame. Did you eliminate them, or does you truck not have them? Also, did you just weld a larger piece of pipe into the X-member to run the pipe through?
Great looking exhaust!

[msgdsrf]

Originally Posted by cdowns

3" exhaust is the hot tip for makin noise and not goin anywhere fast

Yup, +1

Drone

[Fitz]

Originally Posted by 1969Chev

Anyone running 3 inch exhaust coming out before the rear tires? I'm getting my exhaust done on Wednesday and that's how I am getting it. Anyone have any input or any pics?
Thanks!

Putting 3 in exhaust on one of these trucks is like putting lipstick and a tutu on a pig and taking it to a barn dance. The pig gets lots of looks but when the dance is over nobody is standing in line to take it home.

2.5 inch is more than adequate for anything you can put in that truck and you will leave the shop with a heavier wallet. You can always add 3 in tips. I ran 2.5 in straight out the back with the dumps exiting under the steps.

[michael bustamante]

I actually run 2 1/4" with ramhorns and super 40s flowmasters and i have no issues at all. Sounds good and i Dont get tired of the rumble while dring. I gotta add a h pipe though

[RManson]

I'm running 2 1/2-inch stainless on my '68 behind a supercharged LS327. Put out 500hp to the rear wheels on the chassis dyno so 3-inch isn't necessary.

The whole install is here.

Good luck!