I think the low compression might be causing the bottom cylinder to be cleaner/wetter than the top cylinder. The air/fuel charge can’t burn properly with that low compression and goes right thru the motor half burned leaving the oil behind. Wet looking carbon deposits are more common on the 24:1 and 16:1 motors but these 50:1 motors usually leave hard and dry deposits on the pistons and head. Water getting in will usually clean the plug white and leave small rust deposits on it but these plugs look well used and are probably ready to be replaced.
A small amount of water may be getting in thru the lower crank seal as you can see how the lower piston is clean where the intake ports line up. Water getting in here will wash any oil off the cylinder wall causing scoring and galling which causes, you guessed it, low compression. The head gasket may be weeping but if it was blown, exhaust gases would get into the cooling system causing the motor to overheat so it’s probably a mechanical issue causing the low compression.
Ahhh, mid sixties FD’s, great motors!
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