Exhaust 2.5 or 3.0 for a 274

Philv6

Member
Joined
Apr 25, 2003
I would like your opinions, I need a new cat back exhaust. If it was for a stock block 231 I would just go with a 2.5 ATR. Hopefully (if done) I will be putting in a 274 TA headed oncenter motor next summer. Will a 3.0 ATR sytem be needed? If I decide to go with a 2.5 system for noise how much HP might I be giving up? 2.5 vs 3.0 has been discused for stock blocks but I could not find any information about it's use with a stage motor. A single 3.0 would just be too loud.
 
What size downpipe? I ran low 9's with the ATR 2 1/2 and a 3" downpipe.
 
Well IME a single 3" will run measurably faster than a dual 2.5" and is some 20-25 lbs lighter, but either will still go pretty fast, per above :) I put an Edelbrock muff on my single 3" system, which helped the noise some.

TurboTR
 
I currently have a 3 inch downpipe. Bought long before I ever thought about going to a big motor. So I could upgrade the down pipe if that is the bottleneck. So I guess the real question is at what point would a dual 2.5 system become a restriction? Cal you are proof that a 2.5 can go very fast, but was it holding you back? I'm really torn between a quiet 2.5 and the louder, heavy 3.0 system. I heard the single 3.0 is just plain loud. I would like to only upgrade once, but I still would like to stay somewhat quiet and light. I would be willing to give up some HP to stay quiet, but at what point and how much will it cost (HP). It will still be a daily driver. I will be listening to alot of cars this year at Bowling Green.
 
I am gona use a 3.5" downpipe with a 3" ATR single shot.

Of course that's just to keep the neighbors happy when I load the car on into the trailer.

If I were street driving mine, I wouldn't use the single shot. Way to noisey and drones too much. A 2.5 system makes better sense for a street car.....with a dump of course.......for that occasional 9 second pass.

DR
 
I think you answered your own question, when you said you wanted to stay quiet even if it cost you a little hp. The cross sectional area of dual 2 1/2's is greater than your downpipe which has much hotter gases in it. For what you want, I would go with the dual ATR 2 1/2
 
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