Hello all,im a bit baffled and so is the exhaust shop on the exhaust tone emitting from the 425 nailhead fitted with duel through pipes 2.5' inch..we have tried various mufflers and i cannot get a decent big block tone result...i relize all engines sound unique...ive owned various big block engines including 430 Buick ..390 Ford.. plus various other V8 blocks before and never had bad results in regards to the noise emitting out back which has been strong and loud..the 425 has been a task...it just doesnt sound right... Im asking is there something very different about a nailhead 425 verses the 430 or other V8's in regards to exhaust sound/tone and why? ..is it to do with valves/head design/compression?..has any one had the same experience..am i going insane or am i using the wrong exhaust shop...im baffled!!... but the car aint ...Peter..Australia..