If someone brought in a car or truck & it was skipping on one cylinder, the first thing I would check would be the spark plug & plug wire. If they were good, I would have to use my thumb as a compression tester. I would have someone turn the engine over while I held my thumb over the plug hole. If the compression didn't move my thumb away from the hole, I knew there were only three reasons it could be. A burnt intake valve, a burnt exhaust valve or a problem in the cylinder itself.
That's when I would screw in one of my adaptors & apply 90 psi of air to it after positioning the piston of that cylinder at top dead center on the compression stroke. If the air noise came from the carb, intake valve. If the air came from the tailpipe,exhaust valve. If the air noise came up through the oil fill tube or valvecover, piston,rings or cylinder problem.
It was a simple cheap way of finding the root of the problem. Have A Great Ford Day!
