Did you go through the oil filter housing? check out the bypass plunger, if it has one or is it full flow system? The crankcase looks very clean inside. Any deformation in that ball on the pump? Also, did you check the plunger between the pump and screen housing?

I had the head off my Model 12 8T for three years, sitting in the shop waiting for me to get it put back together. When I went to fire it up, no oil pressure with the pony turning it over on decompression. Ended up disconnecting the line to the oil pressure gauge and rigging up a line to prime the pump with fresh oil. That solved the problem. Apparently, the diesel had set long enough that the oil pump had lost prime. Have used it several times since and no further problems

A quick update to all you awesome Caterpillar enthusiasts, I took all your advice and went through each and every one of your recommendations. Nothing seemed to work. I was totally bummed and figured I would call the gentleman I purchased the pony motor from, His family has been in the Caterpillar salvage business since 1942, As soon as I told him my problem, he told me that when they sit for as long as mine did (24 years) I need to put 50 wt oil in until the dip stick is at the full mark and then add 2 gallons of 30 wt, So off to the store I went, And IT WORKED, I can't thank you all enough. The rockers were getting oil and the pressure gauge was topped out, I let it run for about 15 minutes with the valve covers off and the blow by disappeared and its running awesome, 24 years later, I'm off and happy as a kid in a candy store, Ill post picks as my goal is to restore it to like new then take it to the Caterpillar show with my sons and grandkids. Again, bless you all and happy New Year.

Great result, well done.

Great news! Keep an eye and ear on it and keep it in the win column. Great resourcefulness on your part-you came to the right place.

Cheers-
Bernie

Thats good to hear! Great! Is that you in the one pic with a mini mac 6 in your hands? lol

Great work! Your project is coming along nicely.

Well guys now that I got my old girl running, I'm looking to go over the Cable Blade attachment, can anybody send me pics of the manual that shows this attachment, I can't find it in my parts book. My serial # is 9U15770