2.5 vs 3.0 dual exhaust 426 Hemi

Where is the cross over from 2.5" to 3" Dual exhaust on a 426 B-body, full weight street driver?

Is it at the typical 5-550HP range, or does the Elephant gain from dual 3" even in stock form?

I don't know, but my '68 RR Hemi with headers & full 2.5" system didn't seem to be hurting...
4.10 4-speed car, 3780 lbs, dyno'd 540 before fixing carbs, couldn't hook up on 295/50R15 street tires 'til at least top of 2nd gear.
11s with good DOTs on a track.
And you could drive it all day without going deaf.

About 15 years ago, car craft did a dyno test on a 70 super bee 440 comparing 2.5 to 3 duals- the 3 duals gave very significant gains. I assume a engine with even better flow would benefit as well (like a hemi)

I've done at the track testing on exhaust systems, huge gain removing a 2.5 inch system with 2.5 turbo muffs, .9 ET and right at 9 MPH gain
The next street car I built I had a 3.0 inch complete system with the muffs mounted behind the rear end housing and it only picked up .020 ET (two hundreds)and .2 (two tenths) MPH by removing it at a 1/8 mile track
Any thing you can do to improve airflow, in or out, will result in better performance

Years ago I went to electric cut-outs. That way I can put whatever exhaust style and size I want on the car and do not have to worry about choking it. Besides, they are a blast at shows and cruises. Have had them on several different cars over the years. Absolutely one of the coolest mods you can make to your muscle car.

In stock form, I doubt it will gain anything meaningful or measurable. Guys make over 800 hp with 2 1/2" exhaust.. Doubt that a 450 hp stocker would benefit for 3".

When I uncorked by Challenger with 2.5 exhaust it would pick up .4 every time in the quarter, 426 with hooker headers and a slight .510 lift hydraulic cam. Everything else stock. Don't even bother with 2.5 inch.

Some interesting posts, Thanks all!

I think the bro is looking at the TTI 3" system with X pipe.

Anyone have any experience with TTI exhaust systems? Feedback?

There is an Engine Masters episode where S. Dulcich and gang set out to see how much power a 2 1/2" exhaust system would kill on a 625 HP BBC. It lost like 13 HP.

In my experience really depends on the mufflers, if you run turbo mufflers it probably really doesn't matter - both sizes will suck power out of your setup. They will neck down inside to 2.5 inch or less, and you will give up noticeable power.

Straight through mufflers you likely won't lose much with either system, you will probably give up a little with 2.5 inch pipes.

My TTI 3" system on my BB400 Dart Sport is cool. I bolted it all up myself. Fit needed some tweaking here and there and it still has some rattle issues that I need to sort out. Muffler guy with a big pry bar? All of the sound is out the back of the car but it's still a little loud for my taste. This has the quietest (I'm told by TTI) dynomax mufflers they sell. It is coming out of huge by extra large TTI headers. This is weak, little, high gear burnout when I first got it running. It gives you an idea of the sound. TTI 3" SOUND

Nice!