Water intrusion check valve?
 

Friend of mine is very competent drag racer/pleasure driver/engine builder. Take what you will from pleasure driver title. Anyway, he has a 357 he built a few years ago that the deal fell thru on. (Pregnancy induced) Anyway, it has a pretty radical cam, basically as good as it gets for a flat tappet. Anyway, I've seen stuff about a "check valve" to put in exhaust to prevent water intrusion for such an engine. Anyone know anything about it

Re: Water intrusion check valve?
 

I dont know how the story of the 357 relates to a check valve but in regards to said valve I am pretty sure the device you are referring to is specific to the use of marine engines being placed well below the actual waterline. As far as I have even seen in the I/O configuration one of these valves is not needed. The most typical thing one might see is the flapper valve near the exit or over the exit of the exhaust meeting the open air.

Re: Water intrusion check valve?
 

My boat has the flaps at transom, but I've seen in other forums people saying there's something to go in manifolds ahead of water injection to exhaust. Kinda think it's just confused people, but thought I'd ask. Reason why is a big cam with big valve overlap will suck water back during low rpm on the intake stroke.

Guess I should refer to it as water reversion, but my understanding is the big blocks, big displacement engines, are the worst