Tim:

Your comment about letting the engine get to operating temp before "stabbing it" is well taken, and I remember a problem I had with a "D" (40 CUI) Konig in the early 70's. At the time the only piston alternative to the Konig piston by Mahle, were cast pistons made by Stan Leavendusky Sr. Stan of course had much experience casting pistons for the Quincy Flatheads of the time, and for quite some time right up to the end of their competitiveness against the Konig, was the supplier of pistons to Quincy in both replacement and OEM categories.

I had purchased a D Konig that was in bad shape insofar as the bores were concerned, and asked Stan to bore and fit a set of pistons to it. Long story short, I kept sticking one or more pistons as soon as I would open the throttle of the motor after starting and running a lap or so at part throttle, as I was always a believer in taking it easy for a little bit until everything had had a chance to warm up some.

This happened about 4 or 5 times with these pistons, and finally, as I could not afford a couple of pistons everytime I ran the engine, I sent it to Harry ZAK who had started to work on my engines, first with his pipes and cut rotary valve disks. Harry looked at the way the pistons were sticking, just barely a small smear right by the exhaust port and just above and a half inch or so below the ring, and only enough to kill the motor, and then the motor would be free by the time the boat coasted to a stop.

Long story short, he called it a "COLD STICK" and said it was happening because the aluminum used in the piston did not have the same coefficient of expansion as the Konig/Mahle pistons. He (Harry) fitted new pistons (4 Mahle's) and I never had the problem again. Not to say that Stans pistons were bad, but just not the right mix of aluminum evidently for that engine. We also tried various clearances and were not able to stop it from sticking by that method either.

Harry later made some small thermostat housings from billet aluminum and used OMC thermostats for various racers that ran both Konig and Yamato engines, and that seemed to help the sticking problem and also the motor ran much better from the word go, as it would usually take several laps in a race for one to really come on, leading him to believe that the motor was not fully at operating temp until it had been run hard for several laps. In the PRO category, since we only ran 4 laps, and usually took it easy for engine longevity while milling for the start, the engines never really got warmed up till run hard for a lap or so.

The one bad problem with the thermostat housing was that that is was just another place for water stoppages to occur due to picking up trash while running with the force-feed water type pickup, and you really needed a "telltale" so as to be sure you were getting plenty of water while running.