420a no oil pressure on new engine

[Shameless]

So i put a rebuilt engine in my 97 n/t. we had no problems putting it in, triple checked everything so no mistakes would happen. On the first start after warm the oil light would flicker on and after completely warm it would stay on. So i changed the oil pressure sending unit, thermastat, checked the pickup tube for any clogs, checked all seals. no difference. i was in a spot where i had to drive it as it to get to work and it inevitably got a knock from the lack of oil pressure. The pressure was at 25-30 at cold start, 10-15 at warm. Well I put in a new oil pump hoping to fix the problem as well as change the bearing that spun causing the knock. On the next startup after the build the same thing happened. So this weekend we're going to pull the head to check the oil journals for any clogs. but as of now that is just a guess. I was wondering if anyone could shine some light on my cars rainy day. If this next step doesn't fix it I'm running out of ideas. IF ANYONE COULD HELP I'D APPRECIATE IT GREATLY.
Sincerely,
Sheamus

 

[Shameless]

So yeah still stumped, anyone with some wisedom? kind of an odd problem. please help

 

[Shameless]

so we figured out the engine needed a new bearing thats a 20 over. thought that would take care of the problem. no way. back to no psi. any ideas. i really need some help

 

[vr4_3000]

seems that you may have a bad pump or it was over torqued. it could be a blocked passage but I doubt that. i would replace the oil pump.

 

[Locke]

Did you remember to install the o-ring under the pump between the bedplate and upper block? Many people forget this, and lose oil pressure.