Hopefully last thing i need help with before getting motor back in boat this Saturday. Was kicking around the idea of converting my SBC Stainless Marine long risers (dry till 8" from tip-Apprx. 25" from top of riser at highest point) because my new motor and cam selection is quite large from what some have told me. We bumped up compression a good bit and went to a much larger cam with more lift. The though im kicking around is because i do NOT want any reversion but will it really matter that close to the tip where the water and exhaust meet anyway? Boat will idle at 950RPM. I could put a slight ring on the 3" internal pipe at end? would like to convert them to dry and dump overboard but what would that do the the rubber coupler that connects the riser to the tip? Tip had an internal flapper inside tip as well as an external flapper. Any help to get me pointed in the right direction without having to buy a whole new set of risers would be great. I do have access to a very good fabricator if that helps?

434 ci
cam specs are low 240s/high 240s on 112lsa.
Stainless Marine SBC manifolds and risers. Has a slight reversion ring in top bend of internal exhaust tube and riser bend.
was curious also if i could remove internal flapper and extend the exhaust tubing to almost the tip? loud is fine if thats what it takes. we have no noise law.

I would think at 112 you'd be fine with what you have. Dry is basically new tails from SM. There will be no tip and no rubber hose. New tail will go straight through transom.

i have my fabricator do that if it will help with reversion? the internal flapper being in the way is what is basically keeping from having already done that. Is the internal flapper necessary? Can i keep outer flapper in the water is an inch or 2 from the tip then? Exhaust exits bellow swim deck but above water line so i don't want a back up of water.

Thinking about pulling out internal flappers and running center section of pipe down to within 3-4" of exit if tip and seaing off water jacketed part of outer pipe and putting 2 or 3 bungs in it so it has some velocity when it exits so it contains more of a stream yet will still wash down the hotter exhaust pipe? Shouldnt that work and eliminate possible reversion? What size holes in end of water jacketed baffle? Should be same as dry with wet tips im guessing?

I just had my Eddie Marine lengthen my tails.. They now end right at the exhaust tip.. They necked down the outlet and then flared it to help throw the water against the hose. The water outlet is open for about 3" at the top and the rest has a piece of round stock welded around it but is not welded to both pipes allowing the water to drain from the tail...

What would you suggest in my case? Wish id have pictures but my risers are with the motor at engine shop. Where my riser ends (8" before tip exit) and where the tip starts is a slightly different angle. The tip has a slightly steeper angle. Was going to do something like a turndown so the interior exhaust pipe would follow on down the tip why putting the water bungs in the water jacketed portion of outer pipe to give the water some velocity so there is less of a broken water stream to be sucked back up in exhast yet it would still wash over pipe to somewhat cool it. Interior pipe would be exposed about 4" passed water jacket portion and about 3-4" from exit of tip

Pictures would be great.. Hard to picture what you're talking about as far as the "bungs" go..

I can get some but motor is a engine shop getting dynoed and manifolds/risers are with engine. Can get pics once i pick engine up.

I'll say this, I have a very similar motor in specs. 408ci LS2, 10.5:1 242/250 621/613 112ls and I just fired mine up this weekend with headers and instantly got reversion. I had to send my headers back to Lightning to get made dry. I think you are on the right track getting this taken care of before you hit the water!

COREY331 i am going to make them dry until about 3" from the tip. I have an external flapper but am going to take out the internal flapper in wake of room for the 3"internal pipe. the water will exit the 4" pipe about 3-4" before the end of actual exhaust pipe. going to flare the end of the exhaust pipe similar to Boatally Insane to about 3.5" diameter and idle at 950RPM and pray that works. from tip to top bend in riser is fairly steep and has a half moon reversion ring in bottom of top bend also. I believe it will work. also you have a little more valve lift than i do (read in another thread) and i believe my collector will be farther back than yours (appx. 25" from center of top bend may end up being about 28" when its all finished.