Bonanza, You definitely got some problems there. Is this/has been a running engine recently or has it been sitting? At this point, a leak down test (or just compressed air in the spark plug hole) would be a good start. With both valves on that cylinder closed, If the air comes out the carb - intake valve, out the exhaust - exhaust valve, out the breather,pcv, dipstick - rings,ect. A bum cam is also a possibility. Maybe remove the valve covers & watch the rockers move on those cylinders compared to the others, or better, set-up a dial indicator & measure, but I don't think with that low, if it's the problem, you'll be able to see it. I've not heard of Seafoam, I'm guessing it's like GM's Top engine cleaner? I'm concerned with the "pour it in the spark plug holes & then start it" This sounds like a possibility to hydraulic the engine to me. Autolite....Autolite! GM used AC in their vehicles for a reason, also the NGK's seem to be good. Autolite? Lorne