BBC 572 switch to mini starter a season ago worked perfectly. This season starter was grinding after a run . Then got stuck and to switch if for main switch .
today I bough a new starter put it on turned good ignition off to see how it turns . After 3-4 tries the 5 one it grinder switch key off and tried again turned good . Could it be flywheel ring ? Someone had this problem ?

Sure you have the correct starter bolts?

I went thru an issue a while back with starter bolts and a mini starter. Block holes, before threads start, was 3/8". Holes in starter were 10mm. If you have this situation, you need special starter bolts with "stepped knurling". That is, the knurling that enters block is 3/8" and the the other half of the knurling in the starter is 10mm. The correct diameter knurling keeps the starter from moving around and causing alignment issues.

Don’t know . I have a dart big m block and starter is a masterstarter ultra high torque 3.5hp

You had good no issue starter operation before putting this new one in?

Assuming you can access the starter, you can loosen the 2 bolts then re-tightening them but just so they are snug. Then try to move starter. If knurling size is correct, you shouldn't be able to move the starter much at all.

I had a similar problem last year. The flywheel ring was missing teeth.

solonide got stuck and burnt

I but the bolts that came with the starter so I think it’s correct . Will try what you said