Join Date: Jul 2017
Location: Yadkin valley, NC
Re: 1975 Ford F-250 troubleshoot
Do a wet compression test on that cylinder. Squirt about an ounce of your regular engine oil into the spark plug hole then immediately do the test. The oil will seal the ring. If you still have 0 compression that points to a stuck valve.
I'll go out on a limb and take a wild guess that you bent a pushrod, because I bent several myself on my 390 about three years ago. I made the mistake of trying to burn off old gas left in the tank. The 10% alcohol in the fuel had basically turned into shellac, causing several valves to stick, and the weak link was the pushrod.
If that's the case, pull the intake and heads and have them disassembled and cleaned. New pushrods, new gas tank, flush out the fuel lines with brake-klean, and you should be on the road in no time.
1964 Thunderbird 390 V8, AOD, F.A.S.T. EZ EFI 1.0, Victor intake, MSD Ignition.