WTH Flywheel Damage?

[nameiztaken]

What on earth could cause flywheel damage like this?? I was using a Napa starter for the past several months.

 

[imp]

What on earth could cause flywheel damage like this?? I was using a Napa starter for the past several months.

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View attachment 341272

Usually, a starter operating improperly causes chewing of the edges of the ring gear facing the starter pinion gear, but I suspect that is not the case here, since each partially chewed ring gear tooth shows inadequate depth of teeth engagement. I am assuming the flywheel was NOT replaced when the starter was? If flywheel WAS replaced, the replacement may have been too small: several flywheel sizes have been used by Ford. If flywheel was NOT replaced, I am thinking the replacement starter had a pinion gear which was too small: they are made with differing numbers of teeth.

The flywheel teeth completely broken off may be explained by pieces of tooth getting jammed between adjacent teeth while cranking. Whatever happened here, determine exactly which replacement flywheel is needed, and be certain starter used is correct for the application also. After replacement, I would do a test: coat the replacement starter teeth with Prussian Blue, install starter, and crank engine over with ignition disabled. Several seconds cranking. Remove starter and LOOK at transfer of the blue grease onto the flywheel teeth. It should extend twice as deep as the ground off teeth appear, and VERY LITTLE NOISE should be made cranking. That chewed-up ring gear must have made a hell of a lot of noise.