Petrolum Jelly 'Primes' the pump, so it doen't have to try and eject the air in the system before it can do it's work...
Something you should know...
Most oil pump leaks are NOT the gasket at the bottom of the housing on an AMC V-8 engine.
Most of the time, the 'Mystery Leak' is the 'Idler' gear pin that stays in the housing leaking out of the top...
It's usually just a 'Seep' but it's enough to make a 'Neat Freak' loose his mind!
Simply drive the pin out, down through the oil pump housing with a BRASS DRIFT (looks like a punch, but made of brass so it doesn't scar up the steel pin...)
And be careful NOT to ding up the aluminum timing housing as you drive the pin out!
Once the pin is out, CLEAN THE HOUSING HOLE REALLY WELL!
Use Denatured Alcohol or Brake Parts Cleaner so it dries without leaving residue behind.
The next part is MESSY...
Slather the top of that pin, and the hole it fits in with 'Lock-Tite Green', and I'm talking the penetrating thread locker, not the stud retainer... (There are two kinds of 'Green')
And put the pin back in, being VERY CAREFUL to drive it straight in and NOT ding up or crack the housing.
Once it's in, use a LINT FREE RAG to wipe up the excess, and use a little alcohol to remove anything that is trying to stick down,
BUT DO NOT GET THE ALCOHOL IN AROUND THE PIN UNTIL THE GREEN LOCK-TITE SETS UP!
That takes about 24 hours... Just let it sit!
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Once the pin leak has been taken care of,
You can move on to the oil pump part...
Install your 'Gears' (actually called 'Impellers' when they are in a pump) and make sure the side wall clearances are correct with a feeler gauge.
If they pass the side wall test,
Then you use PLASTI-GAUGE between the floor plate and the gears to make sure you have enough clearance between the floor and the gears...
Most pump kits will come with AT LEAST two gaskets, one thicker than the other...
And one or the other will normally give you enough clearance...
DO NOT STACK THE GASKETS! They will blow out EVERY TIME you stack them!
If you don't know what 'Plasti-Gauge' is, then check here,
Summit SUM-PG1 - Summit® Plastigage
This is how you check bearing clearances, or any closed area clearance...
It is a plastic filament of very specific size, and once crushed, it does NOT retract, it stays flat to what it was mashed out to.
You simply crush, then take the floor plate off the oil pump, and use the gauge on the paper flap to read the clearance.
VERY easy to use!
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Once you have VERIFIED the clearances in your oil pump, then you pack that pump full of Petroleum Jelly or Assembly lube before putting the floor plate on the final time...
With Assembly lube or petroleum jelly in the 'Gears', it doesn't have to spin a long time to have any 'Suction' to get the oil into it.
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Also, something you might want to consider in '86 and older vehicles...
There is a PRESSURE BYPASS built into the filter head/oil pump floor plate piece.
Looks like a 'Plug' in the side of it, and has a plunger and spring inside.
You should ALWAYS replace the spring (and usually the plunger) when servicing the pump!
And clean out it's housing REALLY WELL before you assemble it again!
Crud can build up and keep that valve party open, and that will dump oil back into the system without being filtered,
Plus it will dump your oil pressure at the same time!
And I've found LOTS of broken springs down through the years... One of the first places we used to look years ago when people complained about 'Low Oil Pressure'...
Newer 'Chrysler' versions (Can be had in the salvage yards for cheap) don't have the bypass valve and work great.
If your 'Filter Head'/'Oil Pump Floor Plate' has deep grooves in it, then consider a new one,
OR,
You can add what is often called a 'Mid Plate'...
It's a stainless steel plate for the gears to sit on while they work, and it means you don't have to replace your filter head.
