I recently rebuilt the motor in my 2001 Ford ranger 4.0. I have had to pull the motor out 3 times, because it keeps jumping time. What am I doing wrong. Can someone please help me figure this out

 

How is it jumping timing?

 

Eagain. Jumped time so i pulled motor, decided to rebuilt it, after finding it had a tolal of 6 bent valves. After I rebuilt motor, I put it back in got it all hooked up. Started the motor, it ran for a minute then died. Then wouldn't start again. Had another mechanic come over to look at it. He said I had timing off. So I pulled motor again re-did the timing. Put it back in. This time when I started it, it ran real ruff. Then died wouldn't start again. Had mechanic come back again, he hooked up computer, code reader, to it, p1000 came up, and one about not recognizing the key, he pulled intake, and vavle covers to check timing, while doing this a bolt fell down in to cylinder #3 he forced it to TDC. He said timing was still off. Just before I got Rady to pull motor again, I saw the bolt. I pulled motor, got bolt out, removed cam on passenger side, to check valves. Had 2 bent valves again. I just replaced them two days ago, put motor back. It started ran nice and even. Sounded great, I tried to give a little gas and it died. Won't start

 

I've read that the timing gears themselves are not keyed onto the camshafts.
They are a taper fit held by a bolt (I assume).
Did you secure the gears to the shafts well enough?

This is a guess.