Dreadful to hear about your problem, Dave

    My first six port had about 40 hours on it when I also discovered a coolant leak into number 2 rotor.  It also was the results of some overheating before I discovered that I had to "burp" the engine.  That engine was built for me using the stock coolant "O" rings.  I have since used the TES coolant "O" rings in both the rebuild of the six port as well as my current turbo II block and even though I have overheated the turbo II block (trying to get *&^%$ thermostats to work for me) I have had no recurrence of the coolant leaks.  You probably only need the TES type for the "inner" rings, I continue to use the stock outer rings.

    But, I agree, you need to find out why your setup is failing to cool.  As I recall you have a large radiator sitting under the block.  If I recall correctly its sitting at a fairly steep angle to the airflow.  If you are running the engine without a cowl/duct to capture your prop wash and force it through the fins, you may not be getting sufficient airflow through it.  I think someone suggest going to Home Depot/Loews and getting some of that large reinforced clear plastic hose and replace part of your hose runs with that.  I might provide some visual clues to what is going on. 

   After all there are only two possibilities.  Your coolant flow is insufficient to remove the engine heat at an adequate rate from the engine OR the radiator is not rejecting sufficient heat into the airstream (could be a bit of both I guess).  Determining why one or the other of those conditions exists of course is the challenge.  With the clear plastic hose, you should be able to get some idea of the flow rate.  If you wanted to get techie, you could try to time bubble flow speed along a measure section of that hose and using the cross sectional area of the hose to estimate a flow rate.  For that purpose you might want to insert several feet of hose into your circuit some place.

  I would suggest you try these things before tearing down the engine.  I ran my six port for about 10 hours with the leak (but it sounds like it was somewhat smaller leak that you have).  As you well know, not much point in rebuilding the engine with that problem unresolved.  If coolant flow appears to be adequate, then that would narrow it down to the functioning of your radiator.  If you don't have a duct built already, it might be worthwhile to mock one up to direct the airflow more directly into your radiator.

Ed Anderson