I have checked everything I can,,,almost and can't, so far, find the cause of low oil pressure at idle speed when at running temperature. Can any of you FE guys help? ISSUE: When I first installed the rebuilt engine the oil pressure was: COLD: 45 at speed and 25 at idle Running temp (180): 30 at speed and 5 to 7 at idle I replaced the oil pump with a new blue printed Melling HV pump, installed one of the stronger pump drive rods, checked the mains and some of the rod bearings, all perfect, changed the oil to 10w40 and started her up. Now: COLD: 75 at speed and 45 at idle Running temp (180): 45 at speed and 15 at idle To me this is still too low, especially at idle. I have no oil leaks (externally). The engine has screw in oil passage plugs so the rebuilder did the right thng there. Now, I am familiar enough with the FE's & MEL's to understand where all the passage plugs are in the engine. I think I can assume that if any of them were missing (not installed) I would have one of two possibilities. 1) a massive external leak or 2) a massive internal leak. I have zero external leaks, none, NADA. Now, if I had an internal leak from any missing passage plug in any of the main passages, I would have extremely low or no oil pressure at all I would'nt think. Especially once at running temperature. Except for those 4 passage plugs at each end of the lifter galley passages that run the length of the block, if any were missing, I would think that the oil pressure would be almost nil to zero. If the two lifter passages at the back of the block were missing, I would have a major external leak. I don't. To me this narrows things down to the front two plugs in the lifter galley passages. Since the rebuilder installed screw in plugs, I feel almost sure he likely installed all the ones he could readily see. He did an excellent job on everything else. Now this leads me to that sneaky little shit passage plug that resides deep in the block and hides behind the distributor. Since you don't normally put a screw in plug in that one, I am think maybe it was left out by accident. Maybe. Now my question to you FE dudes out there is this. If this one plug was missing (the one behind the distributor) and all the others were in place, couldn't this cause low oil pressure, but not seriously low? After all, this plug is not in a "main" passage. It only holds the oil back that has pressurized the lifters. What do you think? Also, how the fuck to check it out without pulling the engine down?