What I have is a 4.6 Romeo motor in my 2002 f150. We recently changed the motor and put new heads on it. It was in time when we went to crank it over for the first time. Before we put it we rotated the motor with the timing chain on and set in time 8 rotation and everything was fine. But yesterday we finally got everything hooked up. We went to turn over the motoor it turned over a few the back fired. Now when we go to rotate it we can't get a full ration without it stopping. Does anyone have any ideas what would keep it from turning over. Is it possible a nut or bolt fell on to a piston. Or maybe the tranny is in a bind.

 

There are a few things you can try to eliminate some possibilities.
I'm starting from scratch here so bare with me.
The backfire tells us timing is not correct.
Before condemning the trans , if it ran alright before, the trans possibly was not part of the problem.
Crank pulley same /different ?
crank sensor?
Both can affect timing if electrical.
Can you turn the engine over , the correct direction, by hand?
will it crank over with the plugs removed? When we start switching engines of later model power plants, lots of things get into the picture.

 

Crank pulley and sensors are the same. You can only turn the engine over 3/4 of a rotation. After this happen I noticed that the guy didn't hookup all the 02 sensor and a couple things on the transmission.

 

It sounds like timing is off since you can only rotate 3/4 of a rotation. The 4.6 is an "Interference" engine. I would start by pulling the plugs and look for valve marks on a piston(s). You can only add to any damage by forcing the rotation.