I would take a hard look at the valve and the stem to see if any corrosion has taken place. Spin motor by hand to open exhaust valve to check it as well.

have no idea how old your spark plugs are but I would examine that one very close with a spark plug reader or high power magnifying glass. You are checking for water and or corrosion on any part of the spark plug. just some simple tests to possible confirm water or possible not.

BUP, plugs looked fine. I pulled them last year and checked them pretty closely, because I was concerned that I had run the engine lean due to fuel pressure issues.

I did look down at the valve stem and head that were visible through the port, and did not notice any rust on the valve head. Have not spun the motor over to open the valve. Motor only has about 20 hours on it.

whats the other bank exhaust look like ? (the other side of engine) Asking only one exhaust port looks like this and the other 7 are fine ? Is this a carb engine ? or EFI engine, sorry I really do not know your set up.

OK, I think I have figured out a way to pressurize the wet side of the headers with water to check for leaks into the primaries. How much water pressure should I apply? My thoughts are around 40 - 45 PSI should be plenty - the headers should see maybe half of that while running in the boat. Any ideas on this? Going to take a stab at this tomorrow, and possibly apply some heat to the tubes with a propane torch or a heat gun. Still no sign of a big leak - it was still holding about 15 PSI of air, and I know for certain that some of it was leaking past the plumbing plug in the end of the collector.

BUP, haven't pulled the other side yet. Not looking forward to that one - it is on the side with the batteries, and it was a real beotch to get on the last time. I have alignment issues because the boat was originally small block and the transom holes are closer together than for a big block. It is a 489 with AFR heads and a mild hyd roller; 800 Holley. The other three ports on this side look OK. If not a leak, then the only other thing that comes to mind is the possibility that I have a valve adjusted down to tight on #1 cyl and it is not seating all the way. But this thing made nearly 600 HP on the dyno - I would think something like that would have shown up there.

Listen to BUP, he's a very knowledgable guy. Whatever you do DONT GIVE UP! If anything ditch the lightings for something more leak proof if you can't find a solid solution.

Thanks for the comp above ^^^^^

Ok if you think that you have a possible sealing issue with the valve(s) then do a leakdown test as well. Also how about a combustion or ignition / spark problem in that cylinder ?

IMO It looks like that exhaust port / cylinder could has been running very hot to. I wonder if you had some detonation going on. You know a bad valve can suck water ( reversion) to.

IMO possible a valve(s) problem and its causing water reversion to on top of. OTHER possibilities for carbon deposits in the exhaust ports can be blow by (oil) ( ring seal) and or bad / worn valve guides and or valve seals.

I would compression test and leakdown test especially that cylinder.

What I do is cut a piece of the exhaust hose about 1/2 inch long and then cut a notch out of it so it is just barely bigger than the inner pipe. I then clamp the 5 inch exhaust hose to the header where it is normally connected and then using another clamp - clamp down on the 5 inch hose where the cut off piece of hose in installed on the inner pipe. IF done right this will seal off where the water comes out of the header. Then just hook the hose to the water inlet manifold and turn the water on slowly. If there is a leak the water will come out of the inner tubes. Cheap easy way to water pressure test. And water shows up the leak much easier than air.

I think I figured out a way to test it with water. I left the plug in the 4-inch collector inner pipe to seal that off, and slipped the 5-inch rubber hose over the end of it. Then I hunted around the shop until I found something round about the same diameter. I finally found a tin of wax of all things. Plugged it with that and tightened down the clamps. Tomorrow when I have some daylight I will hook the hose up to the water distribution manifold going into the primary tubes and see how it does. I suppose I might have to leave the "cap" or wax tin off the collector at first to allow the jackets to fill up with water, right?



FWIW, when I took my flange off for the air test it was still holding some air. At this point I am starting to doubt that I have a header leak.

Pressure tested with water this morning. Was not a perfect test because I did not have a pressure gauge and I could not get a perfect seal at the end of the exhaust hose, but I am confident that I was able to build at least 25-30 PSI of pressure. No leaks. Hmmm.

I'm tempted just to put the damned thing together and run it at this point. Maybe pull the #1 spark plug after running and look for some moisture. At this point I am confident that the deposits in the exhaust port were not from a header leak.

Might do a quick leak down test on it for peace of mind, but have to get / make one that works right now.