Could be a couple of things but might be that the fiber cam timing gear may have self destructed. . . .
BH,
What is the engine serial number for your 235?
It is stamped into the block on the "ledge" to the rear of the distributor.
That will ID the engine as from a car or truck.
I think that the fibre timing gear was used on passenger engines and the truck engines had aluminum timing gears?
Nonetheless, the timing gear might be your problem.
Group 0.736 GEAR-SPROCKET, Camshaft Timing
