351W Troubles........................

[Jack21]

Like Bruce suggested, take both valve covers off. Remove the plugs so the crank is easier to turn by hand. Using a breaker bar and (If I recall correctly, a 15/16" socket) turn the crank in one direction until you have #1 piston on TDC. Now change the direction of rotation. Any movement of the crank should result in movement of the rocker arms, and distributor rotor. 2 - 4 degrees is typical "slop" on a high mileage timing chain. Substantially more than this indicates timing chain failure, and replacement time.

Fords of this vintage had sintered iron camshaft gears. They were brittle, but not particularly prone to catastrophic failure. Chevrolets, Pontiacs, and Oldsmobiles had nylon (plastic) camshaft gears and when they let go, they were done. I'd guess at this point against timing gear/chain failure.

If, however, you pull the front of the engine apart for a timing set replacement; replace cam, lifters, and distributor gear; and timing set with high quality aftermarket (Not OEM!) steel crank/cam gears, and roller timing chain. (My personal preference is Cloyce, but Crane, CompCams, and other steel/steel roller chain equivalents will work.)