Gentlemen, I am building 2 into 1 for my Heritage (finally, since it's supposedly the best thing, haha).
I got a set of dual headers for softails, that somehow resembles stock dresser headers, except that the split to the left pipe is of small diameter, and the left pipe later balloons up to the normal size. All this is pretty weird, so I am obviously eliminating the left pipe and just plugging in that smaller outlet, thus being left with normally looking 2 into 1.

So, we made an aluminum plug, but the outlet is not a right angle to the pipe, and obviously the main pipe is round inside, thus plugging it would create a weirdly shaped "indent" inside the rear header.
Is that a cause for concern? Should I make a sophisticated plug, or try to fill it up with muffler cement? Or there's nothing to worry about?

 

"Theoretically" you want it as smooth as possible. In practice and in this case in particular, I doubt you will notice any difference. I would not use aluminum, though, on an exhaust system. While the chances of your exhaust getting to a melting temp for aluminum are small, I just don't think it's a good idea. Make a patch out of some other exhaust tubing and mig it over the hole.

 

Your "built" 2 into 1 will not give you the HP boost of a store-bought pipe. Those are tuned exhaust systems.
It is common for the right side of the y pipe to be plugged for "true duals", but always with a steel plug.

 

Thanx Dr Hess and Beemervet for the answers. So I take in my case I can just plug it in and not worry about details.

What's wrong with aluminum plug though? My idea was it expands more than the steel pipe, so will seal the hole well for sure

 

Maybe nothing wrong, I just know that the ones I know of they used a steel plug. Good luck.

 

A muffler shop will weld that up for you pretty reasonable.