*Update*
turns out it was the crankshaft brace blocking rotation. fixed with spacers and it is now running!

Currently working on an engine swap to replace the old 4.0l in my '96 XJ for a new crate motor. in the process of re-bolting the flywheel to the torque converter, i noticed the engine will not make a full rotation. it will only spin around 330 degrees and then jams in the exact same spots. the valves *seem* fine as none of the rods are bent although one of the rocker arms (6th cyl. intake) looks like it's not sitting quiet right. i am out of ideas as to why this is happening because it is in the same spot every time and is firmly stuck and won't pass the marks. i am out of ideas and tomorrow i will be dropping the oil pan to see if it is something in there, but for now, any ideas on what else to check would help. i would like to avoid removing the engine again, and removing the head cause at that point I'd just return it under warranty

 

Did it rotate 360 before you put it into the vehicle?

 

I would take the spark plugs out (one by one).

That is the only thing I can think of that may give you a clue (even an answer)

drop a phone/USB borescope down the borehole

I can empathize, you must be pissed

 

as dumb as it sounds, i don't know. when it was out, i personally didn't rotate it on the stand before putting it in but the people i had helping me said it should have so i'm not 100% sure

spark plugs was the first thing i did and still seizing. rented a bore-scope from autozone and that didn't reveal anything. all pistons seem to be moving fine and hitting both the top and bottom of the stroke but i'll double check. main thing is trying to figure out what could be causing the bind because it has almost complete rotation instead of just being completely seized which is the most confusing part

 

Because the borescope didn't show some piece of trash on top of a piston- Just for the heck of it take the "flywheel"(flex plate) off and try turning it.

....as far as not seeing if it turned before putting it in....well next time
I still wonder if there isn't a piece of trash in there... maybe now stuck to the head. Wouldn't take muchOnly other thing I can think of is piston hitting valve

 

Can you post a pic of the entire valve train and not just the last 3 cyls?

 

fly wheel is good as I noticed the siezing before it was volted back to the torque converter. If looked in the bell housing and there's nothing there. but bad went to worse as its now completly seized. Cylinder walls seem dry so I'm going to try and manually lube them up to get it moving again

 

If that thing is stuck now, considering it's never even turned a complete revolution, I'd start wondering if there's any assembly lube on the bearings.....and start wondering about a lot of other things.

 

Already ahead of ya. Just finished looking at rod bearings and pistons. No damage on any and plenty of oil made it to the during priming. Pistons all move in cylinder but still can't turn the crank. If the crank bearings are fine, I'm gonna pull the engine out and see what it is. I'm gonna feel real stupid if it really is just something on the flywheel

 

*UPDATE*

turns out it was the crankshaft brace. the crank lobes of 2 and 5 were striking it and sticking. fixed it with spacers. not happy that it came like that from the factory but in the end i did get it running! thanks for the help and suggestions.

 

So you got a prebuilt engine from someone....that would not rotate from the shop? I hope you have been on the phone continuously and got some money back from them. Also its usually a stroker that hits the girdle...I didnt think a stock crank hit.