I have a 1990 Miata with the short nose 1.6. I noticed the crank pulley was slightly wobbling didn’t really notice any loss of power. I went to tighten the 10mm bolts a little and one sheared right off easily I tried everything to get the stud out and I ended without being able to get it out I reinstalled it with 3 bolts and didn’t put on the ac belt now it doesn’t wobble sometimes it will sometimes it won’t I haven’t driven the car but does anyone know anything about short nose cranks and how to identify if I need to fix it/ new engine Only 78k miles and well maintained

 

Remove the pulley, remove the 19mm crank bolt, and take the pulley hub off. You can replace this, along with the 4 bolts without even taking the timing belt off. That being said, the damage to the crank happens when that 19mm bolt backs off, and the keyway in the crank becomes damaged. You should be able to see the tip of the keyway once the pulley hub is off, if you rotate the engine over to #1 TDC.

 

I bought a new timing belt and water pump set new bolt timing gear and woodruff key how would the pulley boss come off with the timing belt on it or do you mean just look at the end with the bolt off?

 

On the short nose 1.6s the pulley boss comes off without having to undo the crank bolt.