this is the way i like to think of it. with a small block chevy around 400 ci, you would want at least 2 1/4 exhaust with duals. that is 200 cubes per side. if the motor is hotter, then go to 2 1/2. well a 230-250 is alot of cubes out one pipe. so i would tell you 2 1/4 minimum. 292's need more. on my motor , i have 3" w/ no muffler and when it is spooled up, the dust is really pushed by the force out of the pipe. almost like a leaf blower. tom
