Long time lurker, first time poster. I haven t found anything directly pertaining to the oil pump gear fiasco I ran into on my 2n during the rebuildand subsequent re-rebuild so I wanted to share my experience and what I found to maybe save someone some grief. The long and short of it is, I rebuilt my 46 2n 2 winters ago, The oil pump was rebuilt (new gears and bushing), I primed the pump and it fires right up with good pressure. Shut it down, start it the next morning and I notice it took 10 seconds to build pressure. I knew something wasn t right and At that point I should have pulled the pump and inspected everything but I didn t, and man did I pay for it. I was in a hurry to get my f100 in for some work so I sent the N out the door and ran it like that all summer with no issue. The whole time it would take 10ish seconds to build pressure on hot / cold startup. It sat most of the 2021 winter and in spring of this year I go to start it and it pops right off but the oil pressure never came up, even after 20ish seconds. I shut it down, pull the gauge line, check everything out and try again, still no pressure. At this point I m in almost 45 second of running with no pressure after a winter layup so I accept my situation and order bearings / a new pump kit to see if maybe something got messed up during the rebuild. I pull the engine, send the pump out to get rebuilt again, put it back together and reprime the pump. Fire it up, oil pressure pops up, then I shut it down, wait 5 minutes and start it again, no pressure it keeps losing prime. At this point I m losing my mind, I drop the pan and pull the pump back out and pressure / vacuum test it, it passes. Next I pull it apart to check all of the clearances. At first glance it was fine, even the gear tip to housing clearance measures fine from the top. However, I noticed a normal feeler gauge is fairly wide and more or less kind of binds if you measure from the top, giving a false reading. I ended up cutting some .003 shim stock pretty narrow and sliding it around the gears, there was actually over .008 clearance. I luckily had an old pump with old gears and I measured them with my calipers, both sets of new gears measure .020 smaller in diameter than the gears in the old pump. Yes, I said .020. I found a set of gears on eBay that looked like they were in an older box and they were spot on, I slapped them in the pump, bench tested it and it worked perfectly. Mind you both of the bad sets of gears were from reputable distributors (not Amazon) and both sets were undersized. Long story short, parts quality for these old machines is getting even worse. Even spending top dollar doesn t guarantee good parts. Sorry that was long winded but I hope it helps someone, I knew the gear thickness had been an issue in the past (throwing off the face to cover clearance), but I never saw anything on gear diameters. So if anyone has a fresh pump that won t hold prime and everything else (including cover to gear face clearance / pump isn t sucking air somewhere) checks out fine, double and triple check the gear diameter / tip to housing clearance. Hope this helps.
Andrew
Andrew
