I finally got around to rebuilding a 6 bolt this last month to replace my tired 7 bolt. When priming the engine I noticed I wasn't getting any oil pressure to the head, it was getting some oil but no oil pressure. I went ahead and finished up assembly then did first start Monday afternoon and noticed almost immediately that the cam lobs and lifters weren't seeing oil after running for basically a minute so I shut it down. Then installed a mechanical gauge at the oil port by the turbo oil feed banjo. Started the engine back up and the oil galley that feeds the turbo is only receiving a trickle of oil when the engines rev'd above 2k rpm.
My rotating assembly's seeing the correct oil pressure (12.5-13 psi at 900rpm) as far as I can tell, which tells me its a cylinder head only problem. The heads most definitely a 6 bolt head not a 7 bolt head converted to 6 bolt, which rules out the possibility of the head stud being the culprit for low oil pressure.
The only other thing I could think of possibly being the problem is the HLA dumping the oil pressure instead of regulating it like it's supposed to, but is that even possible? would it be dumping the pressure so fast that it would cease the oil flow to the rest of the cylinder head components?
I did do a little grinding to the oil supply port on the head like many suggest doing, but i did very little. Only ground the area down closest to the stud about 1mm and rounded the curve just a little, so I don't think it would be causing my problem either.
Any suggestions? I really can't think of anything else that could be wrong.