Problem with starter casing cracking/breaking

I had a new engine installed in my 1998 Pontiac Grand Prix. Problem is the original starter cracked with the old engine because I was told the engine locked. Replace with another starter and it broke/cracked again. Now I am told the NEW engine is locked and does not turn the starter. My car has been at the shop for 4 months. I thought replacing the engine was going to fix the problem and I was going to have a New Car; basically without the monthly payment. What could be causing the starter casing to break?

For one thing, the engine doesn’t crank the starter. You mean it the other way around, right? You should have a guarantee on that rebuilt engine even if you bought it from Pep Boys. If the engine is bad have it replaced again at the expense of the person who rebuilt it. It is really, really difficult to crack a starter even if the engine locks up. You probably have a problem with the flywheel, and that may have been the problem to begin with if starters keep cracking.

The starter breakage could be caused by any one of a number of things. Wrong starter, improper tightening of the attachement bolts, or the most likely reason; someone is not checking the starter fit against the flex plate and using the appropriate shims as needed.

The question I have is your comment about the NEW engine being locked. Is the engine locked or is the starter locking the engine?
I don’t know all of the details behind this repair but some of it sounds pretty strange.
Why, or how, in the world does an engine locking up crack a starter? No way can I see that.
And they’ve had your car for 4 MONTHS over this?

Just from what you’ve posted the shop sounds a bit suspect. Maybe more than a bit.