On my modified 302 GMC powered 37 Chevy truck,I used a Flowmaster Delta series 40 muffler,3 inch single exhaust system.It was way too loud for my tastes,even at idle it sounded like an open pipe.I switched over to a Flowmaster "Big Block" muffler,I forget the series,but it's a lot less noise and unwanted attention.
My engine has 9.5-1 compression,fairly rowdy cam and short tube headers which I believe increases the noise coming out the ehxaust although generally, a single pipe tends to be quieter than duals.
I have a short sound video of my 37 Chevy with the Flowmaster 40 muffler,I don't know how to post it on the Internet for viewing,but I can email it to someone who can post it for viewing and listening.
In comparison,I also have a 50 Chevy pu with a stock 235,2 inch single pipe.I got a Magnaflow turbo type welded muffler on it,barely more noise than the stock one.
