Your fiber timing gear was wiped out due to a plugged up oil nozzle. If engine sludge makes it into the 1/16" nozzle orifice it will stop the oil flow that lubricates the timing gears and the steel crank gear will eat the fiber cam gear.
Replacement fiber cam gears are available. At one time you could get over-sized fiber cam gears to compensate for worm steel crank gears.
Mike B
