Do anti-reversion dams work?
 

I've been swapping around risers due to fitment issues. I have Stainless Marine exhaust, and the latest risers that I have are for a Bravo setup, and they go almost to the tips (about an inch short before going into the tip itself). I was curious about reversion with my old pipes so I thought I'd see what these were like since I now have the Silent Thunder off the boat. I was surprised to see that the inner pipes were fairly wet! Farther up the pipe, I see that Stainless Marine had welded in dams that cover the bottom quarter (maybe a little less) of the pipe at its tallest point. Obviously, it is sucking water (which is a surprise because I thought roots-blown engines resisted reversion). Are the dams sufficient enough to protect the engine?

This is the engine installed in the boat with the latest risers. 454, 525 EFI cam, B&M 250.

Any thoughts? Thanks!

I've never had a blown engine but I'm amazed at how strong the reversion pulse is on my 540 strokers. I had to replace my Gil risers this year and ended up going dry with the inner 31/2 in pipe extending 3" past the 4" exhaust tips on the transom. With that set-up, you can still see a lot of water and mist being sucked into the exhaust outlets behind the pipes. The inner pipes & the GGB muffler inserts look wet after it idles for a few minutes. I also had dams welded in about 12 or so inches before the end but I don't believe the water gets that far so I'm not sure if they do anything or not.

Some times I wonder what it would take to build a big LS motor and doing a custom cam for variable marine valve timing. I could maximize performance and still reduce the reversion.