Weird Rapping Pipes
So had a Stock LBZ with twin turbos and 60 over injectors. vvt turbo in valley with s475.No rapping from Y exhaust to two 4" 6' pipes at all.
Bought a Long block with built bottom (Mahl pistons .020) ,Rods, alternative Fire Cam, Ported heads, put a S366 in valley and S480 atmosphere twins, 60% injectors , free flow manifolds and ups. Now have a exhaust Rap that is scary. Only above 3000 rpm and hard load, it I let off throttle a little it stops. I do not mind the sound but afraid something is wrong cause never heard any duramax sound like this, What do you think.