Originally posted by Layman
What is the Theory behind this process???
Reversion is only bad when it sucks water back into the engine. It is the natural "reverse flow" of exhaust gasses encounterd at low engine speed or idle through the exhaust pipe. Larger cams with more overlap have more reversion as a general statement. Gil actually did a study years ago on reversion in their exhaust systems by building a transparent pipe and photographing the water droplets working their way backwards on the inside of the pipe with the overlap pulses at idle.
That's why riser height and water exit location within the pipe is so critical especially with large cams. They will suck water right back into the engine if designed wrong.
Reversion without the water factor though really is just a normal part of the engine running. Once engine RPM increases sufficiently reversion is generally no longer an issue.
Hope that helps.