https://www.youtube.com/watch?v=imt0LJROxtY[/QUOTE]

That reminds me of when I tried a solid lifter cam on a 327. Total milkshake in the oil.
I wonder what cam Ilmor uses?

you need to dump most of the water out the back or sides, and only a small amount dumps into tips, never going to work like this, sons active thunder we just changed to new lightnings is the same way, message me and we can help you out...Rob

I ended up sealing them off to make them totally dry and am dumping the water out of the bottom of the tail before the tip. It's gonna be stupid loud, but I can deal with that a lot easier than I can with sucking water back into the engine. The modification is done, now I just need to get down to the boat later this week to get them back on. Hopefully be out on the water this weekend.

you can T the dump fitting to a very small dump at end of tail pipe, to give appearance of wet, keep the hole small, 1/4" or so and will work fine

I guess technically my exhaust is still wet. Water flows all the way to the end, it just doesn't exit into the exhaust stream. I installed a Merc pressure relief valve before the crossover that regulates the engine pressure to 25psi, the extra is dumped out the side via a thru-hull fitting. I just added 2" to the end of the collector pipe beyond the dam lightning put in outside the transom. I then made a solid dam and welded it to the end of the collector. I slipped the polished outer tail over the new dam and welded it flush on the end. Then between the dam that lightning installed and the dam I built, I made a 1" hole in the bottom of the polished tail for the water to dump. I figure with the water running over the top of the dam that lightning installed, then dropping down to dump out of the bottom of the tail, I'll eliminate any hot spots on the tail except maybe the last inch or so as the water dumps out 1 1/2" before the end of the tip. For protection against wave intrusion I added a set of Hardin Marine polished stainless external flappers. This also covers the discoloring on the end of the polished tip from being welded. I figure this will work pretty good, and if it doesn't, I'm only two cuts away from being back to the way I received them from lightning and can start over, or sell them to somebody wanting to do this swap with a less radical cam and can order a new set from Lightning that are totally dry and dump out the side of the boat with thru-hull fittings.

Hopefully all that work will pay off.

Is there not much "fall" in the tail pipes? Mine have a lot.

ezstriper is my dad and its my A/T hes talking about. My setup is like yours except I have a 1/4" hole letting water into the exhaust about an inch before the tip of the tailpipe to give the appearance its wet exhaust, another hole the same size on the bottom of the tip at the very end to drain the water from the whole tailpipe after you shut the engines off. My 1" hole is on the top of the tailpipe on the inside of the boat, and then I have a 90* fitting in them, with hose going from the 90's to water dumps on the transom sort of like this one from CP...http://www.cpperformance.com/p-12825...p-fitting.aspx

I would imagine with enough fall and the mods you did you should be ok.

Like he said, if it doesnt work out and want any info on my setup let me know.

Thanks man, I really appreciate the input. I'm really hoping that all this work will pay off and I'll finally be good to go. There is a good amount of fall in the headers, Without having them in front of me, id guess there is at least 15-18" from the top of the headers to the bottom of the tip of the tail. I had to lower the holes in the transom an inch to make the tails fit. So hopefully that is enough drop to make it work!! I'll find out this weekend!!

I'm getting reversion with my lightning headers on my LS to. And there extended 6 inches also. But it's running soooo good. Hit 65mph over the weekend. 8 mph faster than the 350 that was in it. Haven't found motivation to take it back apart to fix the reversion. I just try not to idle it fir to long

After all this effort & time, wouldn't replacing the cam with a less aggressive profile be a better solution ?

Not to me. That would require me to pull the entire engine, Order a new custom cam ($400) which would probably take over a month to get. Then I would have the time and expense($300) of re-dynoing the motor so I know what I am working with. With modifying the headers (I'm sure you would call it molesting again) I have maybe $100 in materials and can have it done in a day or so as I can weld them myself at my buddy's shop. I originally sent them back to Lightning for the initial mod because I didn't want any fighting with them incase I needed to send them back for warranty work. But with how long he took on the first shot, I'll just do it myself.

The latest mod seemed like it would work ok when I go it fired up this weekend, but I just wasn't happy with how it looked. So I brought the headers home again and am going to make them similar to TooLateVTEC's set up and dump them through a dual thru-hull fitting in the transom. I'm kind of OCD about how stuff looks and didn't like the way the water dumped out of the bottom of the tails. Plus occasionally a drop would run down to the tip of the tail and could get sucked in. I got home from the lake last night, gonna get them welded up tonight, and will head back down Friday. Thanks again for the help and input TooLateVTEC and ezstriper!!