Re: 1966 FD 20 troubles

[frankr]

I’d say the head gasket is leaking a bit, but not enough to cause such a drastic loss of compression. You need to look further. Pull the intake bypass covers and exhaust cover for a look inside. And go from there, according to what you find. Once you find it, it will be obvious.

BTW, that lower cylinder is washed clean, either by raw, unburning fuel going through or yes maybe water. Water can be coming from the exhaust cover—which you are going to pull, right?