Got a junkyard motor to put in my truck. It's a 4.2 from an 07. I've got it all torn down to move necessary upper parts from the old to the new, and re-gasket everything but the heads.

So that's the back story. Now to my problem. At the exact same spot in every 1 turn of the crank, there is a stop that's takes considerable force to work through. It happens at the exact same spot in every turn, so it's something that moves at a 1:1 ratio with the crank. Would bad main bearings cause something like this?

 

I'm guessing here, but check the thrust on the crankshaft. Some of the 4.2's had some real slop in them, but that might just be the earlier ones.

If you have the motor on a stand then maybe turn it up side down with out the pan in place and see if it is the crank rubbing on something.

 

Engines on a stand. Looked it over pretty well last night, didn't see anything rubbing. When it gets to that spot, it's like hitting a wall. It's a very hard stop