Paul,
Possibly just dreaming, but what grade inconel
is suitable for a muffler 601

Neil.

I don't really know. I always thought Inconel was Inconel.

Paul Lamar

When I was considering Inconel I was looking for 625. I don't remember where
I got that from though. I've since all but decided to use .065 321 SS.

Jay

Unless you're a Goldman Sachs executive, buying new Inconel
from a typical aerospace supplier is not realistic. I was
quoted $1,400 for 8 feet of 2" .049 wall tubing. They would
not sell just one foot. I can't imagine what the cost of a
sheet large enough to form a muffler body would cost, and I
bet they wouldn't sell you only what you need, they
probably would make you buy 4'x8' sheet.
Your best bet for affordable inconel are aerospace
salvagers (generally concentrated in the West) and some
intense internet searching.
I was able to find some inconel tubing scraps on eBay, but
they are all bends of one sort or another. Your results may
vary.

C. Smith

Mr Smith is absolutely correct. I had the same experience
looking for Inconel. The best alloy for our mufflersis 625
but good luck getting it. I finally found a piece on eBay
(in the UK) that I paid $75 for plus $75 to ship it to me.
But I have it. Its .049 thick sheet and it took a couple
months of patient looking to find it. Anyway, keep looking
at the salvage yards and internet and eventually something
will show up.
Best regards and best luck,

John Bell