my 6.5 starts ok but when I get it up to 2000 rpms it starts running very rough. yesterday after getting it to 2000 rpms when i let off it stalled. any ideas ?

Thanks Guys

 

check fuel system for restrictions

 

thats my thought. My harmonic balancer went bad about a month ago. I read in a magazine that when the balancer goes it screws up the crank. Can this be causeing my problems. It only runs rough at 2000 rpms. at 2500 it seems to smooth out.

 

doubtful because it wouldnt run rough as you describe it but vibrate more.

 

A bad balancer will either get you a 2 piece crank, or you get lucky and replace it before that happens. You got lucky. Sounds fuel related, put a temporary fuel pressure gauge on it for now, need to make sure you are feeding it enough. have you ever checked the lift pump?