I'm almost ready for the Exhaust system and wonder what are the Pro's and Con's of both 2.5" or 3.0" and Stainless or Aluminized pipe.
I found a shop that will do an all Custom Mandrel bent system with a "X" pipe for my '70 Swinger with a Mild 440, Try-Y's 727, Mini tubbed.
I would think the 3" is an overkill but I may grow into it later.
What say you?
Thanks.

If I could afford a mandrel bent stainless system that's the way I would go. If your 440 is stock stroke and fairly mild 2.5 in. tubing should be fine and it will be easier to make the bends fit.

I've had 2 1/2" aluminized behind a 440 for 20 years...

The date-code is '94' on the tubing...

I've had to touch-up the welds, but other than that, it looks like the day it went on...


Back then, heard stories of stainless discoloration, and heat retention...

2.5 is good for over 500HP. Id go stainless.

3 inch stainless with mufflers on the kids 62 300.All mandrel and the guy charged him like 325 for all.That was about 12 years ago.Rocky

Rocky,
I've gotten estimates for around $1,600.
Using the 2.5" aluminized pipe only lowers the costs about $300. The expense is in the labor and custom Mandrel bending.
The system is installed from header flange to bumper with those special clamps, "X" pipe, Custom Stainless mufflers and fully serviceable too. Sounds like everything else on this build. OVER BUDGET!

aluminum vs steel on heat is that aluminum is so good at moving heat that it gives it up quicker too.
steel holds on to it longer. takes longer to heat up, takes longer to cool down.

so you will bake things longer next to steel exhaust vs aluminum.

not sure how much it matters due to wall thickness, but it will be noticible.

..why mandrel bends?

I seldom inner purge when welding SS tube, but my experience is it often forms nodules/burrs inside when tig welded, and likely not reachable or visible when welded on long tailpipe sections, and for max flow, that bothers me, FWIW.

That sounds like a ton of cash.The guy that did my kids did it at the time from the manifolds back.He even supplied the SS mufflers.My kid did cut them when he installed the custom headers he bought used.Another guy here was going to make him a custom set of headers for 1200 bucks.I didnt think that was a lot.You can buy TTIs exhasust for around 700 IIRC.Rocky

Thanks for your comments.
Do TTI's fit on a spring relocated to the frame rail and narrowed rear set up?
I need to look into them, I don't think my mods are anything radical that would affect exhaust routing. The only issue might be attaching the TTI's to the Schumacher Tri Y's. ?
As far as issues with the welds, I don't think there will be many welds, most of the connections will be those flat band clamps at service locations.
Nothing is in stone yet.

Just read on TTI's site foot note #57
Leaf-Springs relocated
MUST USE FUEL CELL..........

2.5 is plenty.The F.A.S.T. series cars use 2.5 and they are in the 10 second bracket.

I would go with the three inch system to start with, I also wouldn't have bought any brand of Tri Y headers , but that is me I had set of 2.5 inch pipes coming out of a set of Hooker A body 1 7/8 inch A body fenderwell headers into a set of 2.5 Turbo muffs and then a short set of tail pipes(side pipes almost) on them exiting in front of the rear tires on my 1969 Dart GTS with a mild 440 bracket motor, that car ran 3 runs in the 12.2s E.T. at 109.+ MPH with exhaust hooked up at the old LACR drag strip in SO CA on Friday night, I removed them and the car ran 11.39 at 117.+ MPH on the next three run I built another street and strip car several years later and put a three inch sytem on it with the same headers and that car would run 7.02 in the 1/8 mile at 97.3 MPH through the exhaust sytem that ended at the rear bumper on that car, 1971 Duster with a pump gas 518 C.I. low deck stroker motor, that car ran 6.98 at 97.5 MPH with the exhaust system removed I ended up figuring it was the weight of the exhaust system that made the car a tiny bit faster, not the exhaust sytem restrictions I had the exhaust shop used aluminized 3 inch pipes and a set of 14x7x3 side inlet and center outlet oval Magnaflow muffs mounted behind the rear end exiting at the rear bumper That system flat worked well BTW I used the stock Duster gas tank on that car, but the head pipes from the headers had to go under the rear end (do to the coil over shocks blocking the stock pipe locations over the rear end housing ) and then bent in and up to go between the stock inner sub frame and the outer 1/4 panels I ended up buying the old dart back and bought a 3 inch exhaust system from Summit and had it welded into place the same way, it has the leaf springs moved into the sub frames so the muffs and tail pipes are ran the same way as the Duster but the pipes do fit in the stock location and those pipes go over the rear end housing into the muffs beside the 1/4 panels Those Summit brand muffs sound a lot like and look similar to the Flow Stoppers muffs

I have 3" under my 66 Plymouth Satellite just saying ..

So Cab, do you really think that in your example of going from 109 to 117 mph was because of the restriction of a perfectly good 2 1/2 exhaust system and nothing else? What is that, like 80 hp on a pretty mild motor?

I have more than one example of going from a 2 1/4 compression bent system to open headers that netted 2 mph in 12 second cars.

Obviously your experience is your experience, but logic suggests to me that possibly something else was at play in your example.

i can't believe that mandrel bends would do anything.