tgreese wrote: ↑Thu Mar 02, 2023 11:21 am
From what I've read, the second most common cause of LHIOP is delaminating cam bearings. Some of these engines have that problem. Obviously, this won't show up with a crankshaft inspection. Search and you will find discussion.
The oil pump gear clearance can be measured. If out of spec, it can be corrected without buying much more than a gasket. Naively replacing the gears (an oil pump "repair kit") won't change anything, and could be worse.
Or guess and spend a bunch of money and install the new parts. Up to you. If it doesn't help, then you've tested your guess.
I've read the same thing about cam bearings. Usually that brings overheating and a bunch of other problems with it though, according to what I've read.
I think in this case, regardless of the cam bearings and whatnot, the oil pump kit isn't going to hurt anything, except maybe the wallet a little. If they're like the Buick oil pumps, you can put a steel booster plate in between the gears and the lower plate--it will not only last longer than the aluminum plate but also means you don't have to replace the aluminum one.
As far as the springs go, I have no idea if the AMC ones have springs available, or anything like that. The Buicks do for sure, and I've also read that if you put washers in before the spring, you can make the pressure go up that way too. Supposedly on the Buicks at least, you can add washers until it literally makes the can on the oil filter explode. I have no idea why anyone tried that or would want anywhere near that kind of pressure, but somebody did it.
Changing the gasket exclusively won't change any clearances unless you put a thinner gasket in. It may help with pressure if you have a leak there, but otherwise it won't change anything. Also, since I know you like RTV a lot, do NOT use RTV on these pumps--it is too thick and will cause horribly low oil pressure (and maybe none at all if the gear doesn't reach up to the distributor). The stock paper thin gaskets are the way to go.
I think with 150ishk miles it's not unreasonable to assume there is some wear in there. I wouldn't replace the gears unless you buy/put in a high volume pump, as they last a LONG time. It sounds like your bearings have all been checking out, so I wouldn't put a high volume pump. The only reason yours given what you've said MIGHT need it is if the cam bearing is bad, as Tim suggested. The only other reason to replace the gears is if you take it apart, and like OldFarmTruck22, find that something's been through there and messed it up.
I've never measured the clearances except for around the gears when I installed the extension piece for the high volume function. I know there's a way to, but I think at the stage you're at, you'll know if it's terribly worn or not. If there are chewed up marks from the gears in the lower plate, it's worn. Otherwise it's probably ok.
Also, since you'll be disassembling the oil pump, you'll probably want to take out the distributor and prime the oil pump like you would a new engine. I have gone without doing it before, and just let it run at low idle for a minute or so, and it makes a sucking sound, and then stops clacking, as the oil pressure gauge rises.
Again, not 100% sure how the AMC pumps are put together, or where to find parts, but I know the style, as they work and are put together like the Buicks. Also sorry for another long response.
'71 Wagoneer (DD)
-B350 (HEI, iron 4-barrel, Edelbrock 1406), TH400, D20
-'74 D44 front (nonpower discs)
-custom headliner
-Front shoulder belts (rears eventually)
viewtopic.php?t=23070
There are 2 major differences between new Wranglers and FSJs. FSJs are meant to be both utilitarian and capable, not just capable. FSJs are also rarely initially recognized as Jeeps by the average American.