Oaky, got it, adding a shim impacts excessive pressure so there is no need to go there. The 235 in my truck does not have an oil filter, I recently removed it and installed a braided metal line (same diameter as what was initially on the engine) because the heat from the headers was softening the rubber hoses. I have a new pressure gauge on the car for the 261 and I will take extra care to make sure all of the oil pump connections are well sealed to stop air being sucked into the system. Thanks for your comments.
I'll leave the 235 engine diagnosis for another time and stay focused on the 261. I have a filter for the 261, what should the oil line inside diameter be to maintain oil pressure? Is 3/16" too large?
