Poll - exhaust size

[65 drop top]

I know the topic has been beat to death, but I'm having trouble deciding so I created this poll. Car is a '55 Chevy with LS3 525 which makes about 525 hp and 490 tq, redlines at 6600 rpm's. 99% street car. 1 7/8" headers, the headers are designed for the chassis so I can't go to a different size. Leaning towards Borla or Magnaflow mufflers. Should I go with 2 1/2" or 3" exhaust system. I understand the pros and cons of each. I just think this combo could go either way and looking for opinions. Please vote.

[analyte]

I'm at 452rwhp which align well with your 525hp if that is off an engine dyno. My max rpm is at 7000.

My setup is 1 7/8 stepped headers to a 3in X-pipe then on to 3in tails. I like the deeper tone of the 3in over the 2.5in, but either will work for your application. The key is to use a properly designed X-pipe in your system.

Kerry

[65 drop top]

I'm at 452rwhp which align well with your 525hp if that is off an engine dyno. My max rpm is at 7000.

My setup is 1 7/8 stepped headers to a 3in X-pipe then on to 3in tails. I like the deeper tone of the 3in over the 2.5in, but either will work for your application. The key is to use a properly designed X-pipe in your system.

Kerry

Yes, I'm talking flywheel horsepower. It's the GM LS376 525.

I have an AME chassis for it, and the way it's designed it is pretty much impossible to run an X or H pipe. I'm about the mock up the motor and trans in the chassis so I'm going to look for a possible way to make an H pipe work, but I doubt it.

[Jerems]

I would say 3 Inch for sure. There is only benefits going with the larger exhaust. Watch the engine master test on it.

[dontlifttoshift]

I did a 2.5 in a Morrison TriFive chassis and it was the most miserable exhaust I have ever built.....if it was 3" I would have slit my wrists.

I would run 3" to the muffler and 2.5" out. There isn't a lot of space for a large muffler and they end up pretty far forward so the tailpipes end up longer than most. I would plan on some sort of resonator near the end of the tail pipe to take the bark and rap out of it.

[pittpens24]

Check out the Spintech stuff. Ron is a great guy over there if not the owner of the company. I have a 572 BBC and went from 3 to 3-1/2" which doesn't help you out, but they have very low profile mufflers(which I needed) and the option to run oval(which I also needed) for ground clearance. Options for S/S or Aluminized steel. Oh and they sound amazing!

[Jerems]

Check out the Spintech stuff. Ron is a great guy over there if not the owner of the company. I have a 572 BBC and went from 3 to 3-1/2" which doesn't help you out, but they have very low profile mufflers(which I needed) and the option to run oval(which I also needed) for ground clearance. Options for S/S or Aluminized steel. Oh and they sound amazing!

Do you notice any drone with the Spintech's? I agree on the sound...they are mean sounding.

[pittpens24]

Do you notice any drone with the Spintech's? I agree on the sound...they are mean sounding.

Car is not road worthy yet so I can't comment on the drone. I am about a month plus away from getting my car back from the upholster so I may get a drive in before I have to put it away for the winter

[nicks67camaro]

Do you notice any drone with the Spintech's? I agree on the sound...they are mean sounding.

Spin tech IMHO is one of the best mufflers out there. I had drone masters with a good x and the spintech is so much better sounding. I had zero drone in my old set up was a solid roller SBC 400. My new set up is a LSA (not running yet). It sounded so good. I wish i had a sound clip.

[Ben@SpeedTech]

Couple quick thoughts that may help- I had a nice conversation recently with Boyd at DR. Gas, the inventor of the X pipe and very influential in designing Nascar exhaust systems. His thoughts were that flow is critical right off the headers more so than what's down stream. In my case for example I want to run a single exhaust to save weight and space, so I hit him up to see if that were feasible. He said with my guesstimated 550 hp SBC I could get away with 3" head pipes into a Y and single 3" pipe and muffler. Mine will poke out the side but he said by the time the exhaust hits the muffler it's cooled and contracted enough to not need huge pipe so if I wanted to I could even run a single 2.5" (!) tailpipe out the back if I had tight packaging. Back in the day I had this same motor in a street strip car and ran dual 3" into the mufflers and then 2.5" tailpipes and it ran great, showing again that as the exhaust cools it doesn't nee huge pipes, smaller pipes down stream theoretically may even contribute to keeping velocity up.

I didn't watch the video but it's probably the same one I saw a while back and notice they specifically said they didn't tune the car for the smaller exhaust and left it there. Had they done so the smaller exhaust would have performed better, but I got the feeling they were pushing for the bigger exhaust from the get go.

[65 drop top]

I did a 2.5 in a Morrison TriFive chassis and it was the most miserable exhaust I have ever built.....if it was 3" I would have slit my wrists.

I would run 3" to the muffler and 2.5" out. There isn't a lot of space for a large muffler and they end up pretty far forward so the tailpipes end up longer than most. I would plan on some sort of resonator near the end of the tail pipe to take the bark and rap out of it.

Do you happen to have any pictures? I thought I had plenty of room under there, but maybe not. I do have a kick up in the trunk pan above the axle which should give me a little extra room. And I have a Ricks tank that is centered between the frame rails.

As far as the mufflers go I want to install them under the rear foot wells. The foot wells do hang down slightly into the chassis. I think I can pretty easily slice them open and move them up a little bit. The car is in bare metal so I can make modifications now.

[Razr20]

So I'm just going to throw this out there as I have been going down this road for the last year or so. My car is 75% street and 25% track. 550hp Pontiac GTO with 250hp nitrous kit. As what has been told to me by a few different engine/exhaust experts. I'm running 2.5in Holley Blackheart exhaust all the way back with a Borla 3in tip with 3in electric cutouts at the header collector which extent outward to the side for max flow and HP when I'm at the track. Awesome street sound and great performance with the 2.5in exhaust yet I can turn it into a different animal with a flip of a switch. Not sure if it fits or if anyone else has a difference of opinion..... Let me know.

[MAGONSTERZ68]

LS2 525 hp, auto, 3200 stall, Hooker mid-length header to full 3" duals w/ X pipe to flow tec terminators and Dougs elec cut outs mounted after. Continues over the rear axles and exits behind rear wheels. Horrible resonance at idle when in gear only, will be adding 3" in x 2.5" exit spintech mufflers the for each side, traverse mounted between axle and tank in hopes it kills off in gear idle resonance.

[pittpens24]

Choose your weapons wisely! Was just at a car show over the weekend and one of the vendors had a pretty nice looking '69 Camaro there with a 572 and full 3" exhaust out the back. They had an "x" pipe and round race mufflers. Couldn't believe my ears when I heard that thing fire up - it was absolutely horrible. Had a decent rumble at idle, but when they hit the gas it sounded like a deeper version of one of those massive cans on a rice burner with that high pitched tin sound. Man am I glad I went the direction I did with mine

[1989GTA]

I did a 2.5 in a Morrison TriFive chassis and it was the most miserable exhaust I have ever built.....if it was 3" I would have slit my wrists.

I would run 3" to the muffler and 2.5" out. There isn't a lot of space for a large muffler and they end up pretty far forward so the tailpipes end up longer than most. I would plan on some sort of resonator near the end of the tail pipe to take the bark and rap out of it.

This ^^^^^^ 3" to the muffler and 2.5" out the back.

[Reckn8]

3 inch1 exhaust is what we always build for our A-body cars and use a resonator back by the fuel tank to take the nasty full throttle bite that they make!

[Reckn8]

3 inch exhaust is what we always build for our A-body cars and use a resonator back by the fuel tank to take the nasty full throttle bite that they make!