Hi Mark,
It looks like only you and I have any interest in this thread so I thought I would bring you up to date on the latest, and on my confusion. I pulled the elbow and found plenty of evidence of DexCool inside the exhaust manifold (red crystals), although most were in the passageways to #8, #6 and some #4. The one to #2, which was the cylinder with the most coolant in it when I took out the plugs was carboned up nicely and had little coolant evidence. ??? First mystery.
At this point I was tempted to put in some new gaskets under the elbow and put it back together as the evidence seemed to indicate that the leak must be coming from above. Since the system leaks I doubt it builds pressure. I put air pressure on it when I tested it and that could have squirted coolant down to #2 where as in normal operation it dribbles down the other way. Anyway that could be the story. But I was concerned that while the gasket on the coolant side of the divider did split upon removal (as these new graphite gaskets do) there was no evidence of coolant anywhere on the gasket. So was that the source of the leak? And later I saw that the valve stems looked perfect, which means I was not getting salt from the same gasket complex.
But I had a rebuilt head that has been in the garage for several years and a new gasket set, so I decided to press on and look inside. When I got the head pulled the gasket looked as perfect as I have ever seen. No evidence of leaking around the cylinders or water passages. #2 piston looked pretty good, some carbon and what seemed to be some cleaner areas on the bottom side, like maybe water washing. Ditto for #4 and #6, although there was some general crud that would indicate (perhaps) oil burning and my consumption has gone up the last 200 hours. #8 was fully carbon coated and no sign of coolant stain (even though that was the exhaust passageway that had most of the crystals.
Head story was a little different. Lots of red stain in #2. Ditto for #4 and #6, although also considerable crud that indicate oil burn. #8 looked very normal with carbon and a very small area of red.
I've gone on too long as most of this stuff is contradictory. Maybe it will light a bulb for you.
So my plan is this. I put the new head on and will send the old one to the head shop. They will check for cracks and do a rebuild so my garage spare will be back if it is OK. I will pressure test the exhaust manifold (once I figure out just how to do that) to insure that the very unlikely case of leaking coolant though a hole or crack in that thing is not the issue. I will clean up the surfaces between the manifold and the elbow and reinstall. I have the same gasket set I used last time (the graphite ones) and I know they go on dry. But if that was really the failure I am tempted to try a half torque with hi temp RTV and then a full torque the next day. Bad idea? I hate to do the same thing as last time knowing I was losing a gallon a trip of coolant.
Any other suggestions from you (or anyone else that might chime in) would be welcome. I will probably put the intake manifold/fuel system on tomorrow, along with a new raw water pump. Test the exhaust manifold over the weekend and if good install on Monday. Refill with coolant, change the oil and splash on Tuesday. I hate putting it back together without knowing for sure I fixed it, but I don't have any better ideas.