Sometimes when I try to start the car, the start will turn then stop for a second (as if something is interfering with the process, sounding almost like a clunk), then turn again.
I think this started to happen after my M6 swap. (although it may be a coincidence)

There are no grinding noises or anything and the engine runs fine. The battery has a charge and the alternator is charging well.
Ideas?

 

Got good teeth all the way around on the flywheel?

 

I have good teeth, yea.... wait... nevermind, same goes for the starter.

 

Have you check the starter houseing to see if its cracked?

Alot of guys will put them on with a impact, tweek them a bit and they will screw up exactly how you mentioned.

 

I'll have to check it again, but when I put it on, it wasn't cracked. (I don't use power tools either)

I just recalled of my flywheel fiasco, so it may be related to it. I might need to try another starter if it keeps giving me problems. Thanks guys!

 

I would check as those starter houseings are made out of a crappy aluminum. It isn't strong at all.

I had the exact same problem after I rebult the engine in my firebird.. I put a hairline crack in the starter between the two bolt holes. Probally 1 in every 5 tries you would just get a thud when trying to crank.

 

Yep. That's exactly what mine does. Thanks, I'll check it out.

 

I agree with Alvin, mine has done the same thing in the past.