1st start no oil pressure

just fired up my 88 for the first time and have no oil pressure.oil is moving fine but there"s no pressure. block was completely bare when I got it so when we fired it up the first time it didn"t have the oil relief valve in it. went out back and robbed that from a different tractor. fired it up again no pressure. took pan off took pump off. pickup was really dirty... yea I mustve forgotten to clean it before I put it in. also the pickup seems to have oil in inside it like there is a hole in it or something. but when u shake it no oil comes out. veins are correct according to it manual. put the pump in a bucket of oil and it pumps fine. put it all back together and fired it up still no pressure. my question is am I forgetting something else in the block somewhere? is there another hole that needs to be plugged inside? are my main bearings installed wrong somehow? crank and mains were in the block when I got it... and no were not going just by the gauge.we r taking the gauge wire off at the block I would assume u shouldn"t b able to hold your finger over that hole while its running? the oil comes out of the hole fine there"s just no pressure behind it....

Worked on a 1655 gas once with the same problem after replacing a broken crank shaft found a plug missing near the timing gears thought the machine shop left it out. When we got it back to the customer said it never had oil pressure from new. Some people just don't worry much or enough?

Had a 66 motor rebuilt in a good quality shop AND they left that same plug out, the one behind the timing gears.

That is the best place to look! BTDT. Took my super 55 diesel apart and put it back together several years later, had the same problem. Put the plug in, good pressure.

Well we hooked up a gauge to the oil filter housing and ran it. It won't even budge the needle. Went out to my 77 and have 19 pounds at start up. So since the 77 has a rod knock and has to come apart anyway (just didn't want to do it now) I'm gonna take the pump out of that and put in the 88. That way we can rule out the pump that's in the 88. Speaking of oil pumps we pulled my 880 out of the weeds that I bought a couple weeks ago to rob that pump (motors tight) only to notice that there is no oil pump in it at all, lovely. Did the pump swap and still no pressure. Thinkin it must be the plug behind the cam gear now. Went and looked at a spare block I have and see where the plug should be. I bet that is not in my block. Time to tear it all back down tomorrow night