Big cam cummins miss

Hey guys, I bought an old school '79 pete 359 to use on the farm and would like to get your thoughts on a problem I'm having with the engine. Its a NTC 400 big cam 3, cpl 625 and its missing badly at idle and blowing an excessive amount of white/grey smoke. However under load over 1600 rpm it seems to run fine, the smoke completely goes away, and it seems to have tons of power.

I bought the cummins manual and ran the over head according the book, intake .011, exhaust .023 and the injectors just past finger tight, 2 in lbs seemed about right. Oh and I just had the injection pump rebuild because the throttle shaft was broken.
I also pressure tested the fuel system, and it held air for over a half hour, no signs of leaks around the injectors.
I pulled the turbo and exhaust manifold, and 1, 2, and 4 don't seem to be firing at all, just dumping fuel out of the exhaust ports. 3, 5, and 6 are firing but smoking really bad. I also tried putting a clear hose in the fuel return line, and there seemed to be alot of air bubbles coming out.

Do you think I should pull all of the injectors out and have them tested? I put a new one in #6 (the one that was smoking the worst) and I didn't seem to make a difference. Do you think I have a cracked head somewhere? There seems to be alot of oil around the back head, but its hard to tell if its coming from the head or the rockers.

Any ideas would be appreciated, thanks!

 

Thanks for all the replies! I'll recheck all the injectors maybe I set them too loose. When I ran the overhead all the valves were tighter than spec, is that normal? Also, someone told me to check the fuel tank for coolant, so I did and found a teaspoon or so but that was all. So could that mean a cracked head or injector sleeve?

And it was originally and big cam 1, cpl 324 I think. According to the tag it was rebuild in '88 as a cpl 625. Someone told me that meant it was a big cam 3, not sure if thats correct or not. Also, I'm pretty sure it doesn't have mechanical variable timing.