To the best of my skills I ran a leak down test on both of the "bad" cylinders.
In both cases, the only place I could find air coming out was the oil filler hole.
I had both pistons pretty much at the top of their stroke for the tests. One, the front one, I had at the top, but had air escaping the exhaust. Further cranked it to the top again and that quit with air only escaping the oil filler cap.
I did notice my radiator was very low and got it up a little higher, but there was no bubbling there. Oil level was normal and did not appear thinned down by gasoline, although I can't say for sure.
I had carb wide open. I had oil filler open, pvc opening open, dipstick open, radiator cap off and all plugs removed. Should I have removed the pvc from the hose to the manifold instead?
My instructions with my leak down tester did not mention what air coming out of the oil filler meant.

 

I got my new head for the 240 last week and got it running. My compression numbers were 90-95 wet and dry in five cylinders and 75 in #4.
It now runs smoothly, idles like a charm at 500 rpm and has more throttle. These little sixes are not powerhouses but I feel some more power on the freeway. I can now hit 70 mph. I do not yet have a reading on mileage.
The tab was $ 740 including gaskets, new seats and two new valves and odd hoses and belts. Pricey, but here in the SF Bay Area, everything is. Shop labor is $110 per hour.
I am pleased. These I6's are a dream to work on but the head weighs a ton. You need two guys to R and R. Actually, we used three with the head dangling from a 2x4.

Good luck to all.