Dual exhaust


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By rmk57 - 16 Years Ago
I have 1957 Custom, 272, auto, and I'm going to dual exhaust from the single thats on it. Is 2.5 inch overkill or would that work okay.
By lovefordgalaxie - 16 Years Ago
I have a '74 Galaxie with a 292, and dual exhaust. It was single exit from the factory, just like your car. I eliminated the Y connection, and ran dual 2.5 inch pipes all the way, with an H balance intersection just after the tranny, and one glasspack on each side. When I did the job, the car felt more "loose" with the dual exhaust. Nothing bad happened, so I think two 2.5 inch tubes is ok for your car.

One very interesting thing is that the exhaust sound got lower (I had one single tube, already with a glasspack). I was surprised, but is logical, since that with just one tube, all the engine gases will pass trough one glasspack. With the dual sistem, the gases will pass trough two glasspacks, and the sound will result a little lower.
By BIGREDTODD - 16 Years Ago
OVERKILL, in my humble opinion...the duals on my mild-cammed 312 in the T-Bird MIGHT be 2", no bigger...ran just fine, thanks...

I have dual 2 1/4" exaust on my 500" cadillac in my '60 F-100...it also does just fine... 

Look at your collector size on the manifolds...anything much larger than that would seem to be a waste...and a waste of $$...the tip size will make wondrous changes in the note without effecting torque...

My 2 cents, and my experiences...

By charliemccraney - 16 Years Ago
I don't think it will affect performance significantly. If anything, I'd go 1/4" larger than the manifold and that's it. If anything, keeping it as small as possible will ease the installation. Think about instaling an H or X pipe while you are at it.
By rmk57 - 16 Years Ago
The outlet on the exhaust manifold looks to be about 2 inches. I slid a piece of 2.5 up to bottom of the manifold, looks like sewer pipe hangin off it.w00t
By Ted - 16 Years Ago
rmk57 (10/25/2009)
I have 1957 Custom, 272, auto, and I'm going to dual exhaust from the single thats on it. Is 2.5 inch overkill or would that work okay.
Going to 2½” sizing on the exhaust can potentially reduce the backpressure to the point that the fuel mileage during cruising will take a dump.  2” pipes with a crossover or H pipe is what I would recommend for a daily driver and where fuel economy is a concern.