OK, so I finally got my LS motor in the boat and fired up today. Motor fired right up and sounds great. But I ran into a problem, you guessed it, reversion. Here are the specs

408ci LS2
cam: 242/250 621.5/613 112ls. Cam came from Bob Madera
Exhaust: Lightning Headers with extended collector

Everything is brand new on the engine and headers. The motor ran perfect on the dyno.

After firing it up and getting the idle set, I let the motor run and warm up. After it was good and warm, my buddy noticed a drip out of the 2nd to back header primary on the port side. Upon closer inspection, it was coming from between the head and header flange. I instantly killed the motor. We pulled the header and there was probably a teaspoon of water in the back two primaries. I then pulled the other side, and it was the same way. So I pulled the plugs and cranked the motor over to get any remaining water out, then fogged the cylinders. Checked the oil, and it was slightly milky, so it has been drained.

Here is a pic of how my headers are made showing the extended collector




When the header is installed that extension is only 1-2" away from the back of my exhaust tip where the flappers are. I just put in new flappers and was wondering if maybe the water is coming out and hitting the flapper and bouncing back into the collector? If it just reversion from the cam being a little to aggressive, my only options are having new dry headers made or taking the flappers out and extending the collector well into the tip, but then I risk the chance of having a wave hit the transom and swamping the exhaust.

Just looking for some input on whether it would be worth trying to take the flappers out and firing it up or not? I really don't want to hurt the motor by getting more water into it. Any help is greatly appreciated!!!

Are the rear two cylinders primaries both on the bottom of the collectors ?

Also, a water drip at the flange would tell me there is a gasket leak there...which can cause reversion in of itself.

Yes, the rear two cylinders are on the bottom of the collector. And I agree, the drip shows little exhaust leak, but I really don't think that's the cause of the water since the other side had the same problem but no drip. In all actuality, I'm happy there was a drip. If there wasn't, my buddy would have never seen it and I wouldn't have known there was a problem till it was too late.

Needs a dam on the bottom between dry and wet section.

Cmi and revolution marine does this. Eddie marine just started as an option. Lightning should too as some others have run into this too.

What do you mean by a dam? I've never heard of that. Thanks for the input!!!

Here's one in a basic exhaust manifold:

Gotcha. Thanks. That looks like something that would have to be put in the collector since it actually sticks out farther than where the water is introduced.

Yes, in collector, but no, it is before the water enters the exhaust stream. This way, when water is sucked back, it hits this instead.

Cup your hand halfway, tilt at a 45* angle, and you'll see what it will basically look like put into a header collector.

If you look at how my headers are built, the exhaust part of the collector is necked down to 3" and extended out past the end of the larger collector where the water is introduced. So the water actually enters the 4" exhaust hose that connects it to the tip before it ever comes in contact with the exhaust. So to put a dam in, it would have to go into the smaller exhaust part of the collector.

Yes, exactly..... In the 3" dry part. I would put it further back towards, but not right at, the primaries because if you out it towards end of collector, water from top of collector can and will fall back into dry part as it runs over and some is sucked back. CAll Lighting and see if they have ever done this. If not, they should. Like I said, some of the other exh companies have learned this and do it standard or optional..depending on the company.