Question for the cam guys
 

I installed this cam kit (see link below) in my new engine and a few folks brought up the possibility of reversion but were not for sure. I would like some more opinions before I sink a ton of money in an exhaust system this year or if I can get by without it this year and upgrade the exhaust next year. It's a SBC with stock Merc manifolds and risers, thru transom exhaust that exits about six inches above water line at the back of the boat while at idle speed. So in another words the tips are always out of the water. Any input or experience with a similar setup would be appreciated!!

http://sdparts.com/details/gm-perfor...parts/12480002

Thats a borderline cam for water reversion, especially for stock manifolds. Also your manifolds could be corroded making the problem worse. Reversion is not about where the tips exit the boat, its where the water from the exhaust enters the manifold and then the engine sucks water back into cylinders while its running. Some performance manifolds are a lot better at keeping water out with aftermarket cams than the stockers. Your cam has a 112 LSA, while a 114 is usually used as the minimum to be sure no reversion happens. Hopefully someone with more experience on SBCs chimes in as I have played mostly with BBCs

If you can swing a new exhaust I would do it, because you are going to see very little gain from that cam alone. And it wont do you any good to wait until next year for manifolds if all your valves are shot or you hydrolock the engine

+1 to the above... Look at stainless marine, they make a nice set up for small blocks...Also do a seach in the swap section, there was a set of stainless manifolds for a good price.

I'll give it a +2, well said

Tried to find the post in the swap shop but no luck. Is there any specific type of riser that I need? Can I put aftermarket risers on stock manis to get by for a season or is the manifold itself the issue? I understand that the water mixes with exhaust but how far back does the mix need to be? I'm kinda lost here, sorry guys. I appreciate your help I really do

There are so many things that contribute to reversion other then just lobe sep. I would have no fear of running that cam with the stock manifolds. Let it idle for a bit and pull a riser off right away before it cools down and condensation starts. You'll be able to tell if you have an issue.
If you can afford better manifolds now your engine will be able to take better advantage of the new bump stick. Also, a lot of engine failures are due to water leaking at the wet joint on factory manifolds.

When you say wet joint are you talking about where the riser bolts down on the manifold? And when I pull the riser where am I looking for water? Down inside the manifold?

87Magnum, FWIW, I was running a comp cams 226*/236* @ .050 .540/.547 on a 112* LSA in my 454 with stock exhaust and silent choice with no reversion issues. Of course, big block and small block are two different animals, so I don't know if that would make a small block less or more prone to reversion. I have read that larger cubic inch engines "see" a given cam as milder than smaller engines, but conversely, I have also read that the larger piston/bore/stroke "pulls" harder on the exhaust stroke overlap. I personally feel like you will be OK with the short duration on that cam. A lot more can be read into it with the actual valve open/close events rather than duration and LSA numbers.

I will see if I can dig up the cam card as it has all of the other info you mentioned and see if that helps

Duration numbers are usually smaller on SBC. They cannot be compaired to BBC specs.