The vehicle: 1976 F-250; 460; C6; aft axle and (driver side) mid-ship fuel tanks; stock exhaust.
Stock exhaust consists of stock cast iron exhaust manifolds discharging into 2-1/2" exhaust pipes. Both exhaust pipes discharge into a single muffler on the passenger side of the truck. The exhaust pipes & muffler combination was serviced under part number D5TZ 5230-BM. The muffler discharges into a single 2-1/2" tailpipe which exits on the right side of the truck behind the rear wheel.
The exhaust pipes and muffler are in excellent condition. The tailpipe was somewhat "patched up" due to the effects of corrosion.
As the truck is driven very conservatively only on the street, I would like to replace the tailpipe with either two 2-1/2" or one larger (3" or 3-1/2") custom bent stainless tail pipe(s).
The problem is that I don't know the internal structure of the stock muffler, and if such a proposal is feasible.
I'd appreciate any advice regarding the internal structure of this muffler. I suppose that I could cut off the muffler's rear cap and restructure the internals, but I'm trying to make the job as simple as possible.
Thanks for any advice.

 

Best bet there would be to get a "dual in dual out" muffler. There's no one way I'm aware of to restructure your existing muffler to go from one to two tailpipes. Granted, you could always add a Y pipe after the muffler to give you two tailpipes, but that doesn't really accomplish much but drain the wallet.

Single 3" out is doable with an adapter from your local Mc.PartsStore. However again you're really not gaining much. Why not just replace the stock 2.5" tailpipe?

 

A dual 2.5 inch inlet, single 3-inch outlet muffler is perfectly acceptable for your configuration. Choose one of a reputable brand.. Magnaflow, Borla, Flowmaster, etc.

 

Do the current pipes (2 1/2"?) from each cylinder bank merge before the muffler or at the muffler?

Merge before the muffler in a "Y pipe" would be a common stock setup. Merge at the muffler would probably be retrofit.

 

I could, but I was hoping at the same time to get a bit better "breathing" for the 460 by increasing the outlet size on the muffler.

 

That has been one of my considerations, and I have been looking at what the industry has to offer, but since the existing muffler and exhaust pipes are in such good condition and "fit" so well, I thought that I'd first explore the possibility of modifying the outlet cap of the muffler to accept either a larger pipe or two 2-1/2" tail pipes.

 

Rear (outlet) cap on muffler connecting to single 2-1/2" tail pipe


Two 2-1/2" exhaust pipes from engine connecting to front cap of muffler


Muffler on truck showing driver side mid-ship fuel tank in foreground and driveshaft between them. Stain on muffler is lube spray from recently greased U-joint.

This arrangement is original, as confirmed by drawing in the Ford truck parts book. Please excuse the green tint. My work light was fluorescent.

 

I was fortunate enough to get a Flowmaster dual 2.5" in/out for my 460. Had the exhaust routed out behind rear tire. Love it Engine breathes easy and sounds great. Concerning one of your comments earlier, your engine will only breathe as easy as the smallest restriction.

 

I had some take-off 2.25-inch in and out Flowmaster 40s but needed 2.5 inches in and out. Come to find out they were the same internally so it was just a matter of cutting off the 2.25s and welding on 2.5-inch ins and outs.

 

Thanks to all for comments and ideas. I'll be doing a bit more research before deciding on the path to follow.