Just finished installing my motor now I need exhaust and muffler help. I'm running a 470 stroker with a 3" collector. Should I run a 3" exhaust with 2 1/2" tail pipes or just run 2 1/2 all throughout?

My 451 has 3" with an X-pipe back to the mufflers so far. MO requires tailpipes of some sort. I'm still waffling over whether to make 3" or 2.5" tailpipes. The smaller tailpipes will be quieter and easier to route over the axle and won't hurt flow much.

I think 2.5" from the headers back is too small for a 470 unless it's built for street "stump-puller" (low rpm torque).

any pipe restriction (less than 3") with your 3" collectors from the collector flange rearward hurts you and not sure how much I go with this but many have said that reducing to 2&1/2 for tailpipes is acceptable cuz of the gasses cooling & shrinking & looseing velocity. #1 is noise management (how much are you willing to tolerate) VS max output. I think the best system is 3" cutouts right at the collectors either vacuum or electrical then T'd from there with 2&1/2" rearward with restrictive (quiet) muffs. this way the power and the noise is under your control & only there when you want (need) it. We ain't teenagers anymore. with the money in the hands of a (neutral) third party you open it up & ten seconds later it is all over ex the crying (collect your money/shake their hands/call it good!). they will never know what hit em

Use the three inch if your after max performance, I would mount the muffs as far back as possible to allow the exhaust gases to cool and that will make it a tiny bit quieter also. My last two cars with three inch pipes had the muffs mounted behind the rear end between the 1/4 panels and the rear sub frames exiting with 45 degree turn downs at the rear bumper My next car will have 3.5 inch pipse all the way back with those muffs mounted the same way

I've done the 3" to mufflers and 2.5" tailpipes on 2 cars and my butt-dyno couldn't tell the difference. But my ears could.
Gonna do the same thing on the new project.
Cab's right: the sound levels that I enjoyed @ 20 on my street cars are irritating to me now @ 64.

thanks for the input guys. looks like I'll go with the 3 inch and 2 1/2 tailpipes and dynomax ultra flow mufflers.

With my 493 I run the 3" TTI system and my tailpipes are 3" also. But honestly 2.5 tailpipes with a 3" system should be fine. Its not like you worrying about every hundreth of a second if it is any slower but I dont think it will make any difference with 3" or 2.5" tailpipe for you. Ron

when the time comes if you need more quiet You can add a pair of glasspacks in the tailpipes alongside the leaf spring. shop carefully as alot of em neck down significantly on the ends where the nipples are welded to the main case and the louvers are punched inward which hurts flow & going with 3" ones is an option

I'll ask a silly question, what kind of power are you making?

Agree the 3" exhaust is worthwhile with the 470... also the 2.5" tailpipes should not hurt much though I'm not sure what the benefit of smaller tailpipe is.

The 3" TTI system on my '70E goes over the axle fine even with rear sway bar.

I have 3" though the mufflers and 2 1/2" tailpipes and I love them. I added 12" mufflers in the tail pipe because I didn't like the drone

thanks for posting that video Feets. EDIT I was thinking it also said that below 3500 it is way less of an issue. for the street you've gonna be under that quite a bit of the time

Very interesting. Quite a drop in torque and hp with 2.5" all the way to the collectors, as expected.

But has anyone tried the combo we're talking about (3" to the mufflers, 2.5" tailpipes)? THAT would be really interesting to see on the dyno...

I would do the 3" from front to rear and not bother with the small tail pipes.

Is 15hp and torque really a big drop with a 600hp motor?

I haven't had a chance to dyno it yet. But it's a 400/470 stroker running a solid cam 240/250 lift I believe, trick flow heads, and of course the 1 7/8 headers. Hopefully it's at least making over 500.

My mild(very by you guys standards lol)496 has never been on a chassis dyno so I can't back it up.I have 1 7/8 headers (C body) with 3" from the collector to the x-pipe and then 2.5 back from there.Flowmaster mandrel bent tail pipes from a B body with some extensions before the turn downs.My X is an old Dr. Gas x pipe that is 3" in / 2.5" out.In fact the whole system came from my old Charger 15 years ago.
I hardly ever drive it anymore but if it would pick up 20hp and tq I might would redo it.
If I had to guess I would say mine makes 525 at the flywheel and maybe 550 tq.

if I had a 3 into 2&1/2 system up & running right now I would seperate it at that junction(s)/pop in some ear plugs/see what the butt dyno says

13 hp difference on a 615 hp engine. Probably less than 1/2 of that at 550 hp, and probably no difference at 500 hp.