Thrush Welded/Flowmaster knockoff sound?

[hillytim69]

Hi guys I have been away from the garage for a while (other projects) such as a new baby girl last week... but finally had an exhaust put on my 75 Stepside with the 383. Now can hear things a little better. I've never ran Flowmasters or chambered mufflers in the past, usually just ran Super Turbos or cheap turbo muffs. This time i thought i'd try something different and got the Thrush Welded (Flow knockoff) mufflers. I have a mild 383 10:1 compression, Summit headers into 2.5 piping then mufflers and turndowns before rear axle. I don't mind the tinny sound but is it normal to hear a bunch of pinging/rattle noise on part throttle accel? It kind of sounds like detonation but i really dont think it is. I run 91 octane non-oxygenated gas and retarded the timing a bunch by hand and it always sounds the same. Of course i have no floor mat in the cab and a couple holes but still... Do you guys think I'm hearing exhaust pulses banging around all over the place under the truck or what? I'm thinking I'm gonna put some stock manifolds and y-pipe on with a quiet muffler and see if it goes away. I really don't think its from the engine or detonation but it sounds similiar. Maybe I'll advance the timing to make it ping and testdrive to see if its a different noise. If this is what the Flowmaster/and flow knockoffs sound like I don't like it. Opinions welcome. I told my wife if this thing blows, I'll have to do a big block but I don't think thats gonna happen. With all these kids now I'll be spending most of my time behind the wheel of the Odyssey minivan.