Vintage Mustang Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
4,193 Posts
Discussion Starter #1
So much is written about the proper sized pipes for our dual exhaust systems (based on each car's individual horsepower ratings). And nearly everyone insists that the mandrel-bent pipes are the best because their bends don't reduce the pipe diameter. Consistent, unrestricted flow from the headers back through the tips; makes sense to me. But I had a thought... No, really - I did! :p

If my car should have 2.25" piping - why couldn't I have my local shop fab up a 2.5" system for me? Their non-mandrel bends would decrease the diameter to just about 2.25", wouldn't it? Wouldn't the end result be about the same as buying a pre-fabbed 2.25" mandrel-bent set-up? The advantage would be an exact fit and correct routing through my GT rear valance. Any opinions?
 

·
Registered
Joined
·
6,630 Posts
You could do it that way, its just harder to fit 2.5".

Building an exhaust out of mandrel bends can be done at home if you can cut and weld.
 

·
Registered
Joined
·
4,193 Posts
Discussion Starter #3
Building an exhaust out of mandrel bends can be done at home if you can cut and weld.
Well, yeah. But that can be said for anything, can't it? If you have a spray gun and booth, you can paint your own car; and if you have your own rubber tree and mold, you can make your own tires. :: Let's just say for the sake of arguement that I don't cut or weld or have a lift...
 

·
Registered
Joined
·
5,066 Posts
mandrel bends are nice, but I wouldnt kill myself to get them. I always favor choosing the mufflers and tips you want, and heading to your local competent muffler shop and have them weld in the system you want. Kits from a catalog cannot account for every part, twist, bracket, whatever you may have hanging from under your car....plus, you can be there and answer questions, tell the guy exactly what you want, etc.

Long way to say that I wouldnt consider mandrel bends a showstopper at our power levels. Plus, your local shop may have mandrel-bent pieces available that they can weld in as they go.
 

·
Registered
Joined
·
10,006 Posts
Go buy a 24" section of 2 1/2 inch muffler tube. Then go under the car and see that the pipe is gonna be real close to the gas tank on the drivers side. because it fits between the spring and the fuel tank.
Another thing: the fit diameter will incrrease in both directions. both up and down. So, the tailpipes might get closer to the trunk floor, and, the rear axle.
 

·
Incorporated Sell Out
Joined
·
17,130 Posts
Well I know from experience that 2.5 bent over the axles and out GT valance style work just fine...however...I think even that is overkill for your application anyway...2.25 should be fine in your car.
 

·
Registered
Joined
·
326 Posts
The change in diameter from 2.5 down to 2.25 and back up acts as a restriction to flow. Anytime the pipe goes up or down in size, there is flow disruptance. The only exception would be a properly built venturi.

I would guess that 2.25 mandrel bent pipe flows better than 2.5 non-mandrel bent. No basis in fact for that. Just a guess.
 

·
Registered
Joined
·
6,630 Posts
Yeah, but I HAVE been cutting mandrel bends to make an exhaust, and it IS do-able. (And anyone who buys a lift shouldn't work on cars ;) )

On the other hand, exhaust isn't overly sensitive if you are just doing basic bolt-on stuff. The exhaust shop can set you up well, and the only real concern is if they will get you enough ground clearance. For that reason make a point of telling them you want those pipes tucked up there real-purty-like. ::
 
1 - 8 of 8 Posts
Top