Did a leak down test on the newest project today. Pretty decent, worst one was 22%, best was 18%. But, I kind of guessed at TDC too, I just dropped an extension into the cylinder through the spark plug whole and rotated the crank until it was at the top. So considering I may not have been exactly TDC on all cylinders, I'm happy with the numbers. Also further evidence to me that it doesn't have a cracked head. So, I flushed the cooling system and put a new thermostat in it. Have to grab some distiller water and antifreeze in the morning so fingers crossed.