Hi guys. I have never seen anyone do this before, but maybe I missed it somewhere. Anyway, it applies to Gen 1, 2, 3, and 4 LSx engines. Maybe this post should be somewhere else on the forum. If so, perhaps a Moderator can move it to a better place. I'm much more a mechanical guy than a forum guy, or I would post pics! Anyway, my priming tool is virtually FREE with just a small amount of work on your part. Here goes:
When most of us get a new timing chain and gears, we usually pitch the old timing gears. DONT DO THAT!!! You'll need the "old" drive gear.
Step 1: Get some "flapper" wheels that you spin in a drill motor. Be sure to get the right size, so when you spin the wheel, it will remove material from the drive sprocket/gear.
2: Place flapper wheel inside the drive sprocket while holding sprocket in a vice, or have some sort of device that holds the gear stationary.
3: With flapper inside the gear, spin it with the drill motor while moving the wheel back and forth, much like a hone.
4: Keep trying the altered gear on the crankshaft until you can slide it on and off the crankshaft, and spin it freely.
5: Use an existing piece of 1/4"-1/2" thick (doesnt have to be exact) piece of bar stock (or buy a small piece at a local TSC or Home Depot). The bar stock should be 1/2"-3/4" wide, maybe 3" long. You'll need this piece later.
6: CAREFULLY centerpunch 2 holes 180° apart, into the "meatiest" part of the sprocket, on the "toothed" end. Try to make them equidistant from the centerline of the sprocket, say 1" from centerline of gear, maybe 2" apart, or 1-1/2" from center, 3" apart. I dont have my sprocket with me, or I'd give more exact dimensions. You're basically building an oil pump drive that your drill motor spins. Anyway-Using a 13/64 drill bit (a drill press would be easiest way), drill 2 holes at least 1/2" deep into the timing gear. Now, using plenty of cutting oil, or old motor oil, CAREFULLY tap the holes to a 1/4-20 thread. If you break the tap, you're screwed!!
7: Heres where your bar stock strap comes in. As close to the centerpoint (both width and length) of the piece as possible, drill another 13/64" hole, this time drill it through the stock, then tap for another 1/4-20 thread. Now, back to your timing gear/sprocket. Whatever distance apart you drilled the 2 holes in the sprocket, you now drill 2 clearance holes in your bar stock/ strap. These holes should be around 3/8" diameter, and evenly centered from the middle 1/4-20 threaded hole.
8: Using (2) 1/4-20×5/8" long (length will depend on thickness of your bar stock) cap screws/bolts, snug the strap to the sprocket.
9: use or acquire a 1/4-20×1/2" long socket head/allen head cap screw, and, using loctite, tighten it firmly into the center of your strap.
10: After oiling both the 1st couple inches of your crankshaft AND the inside of your modified timing gear, slide your modified timing sprocket/gear onto the crankshaft and carefully guide it into the oil pump drive gear. You obviously cannot do this with the timing chain and gears already in place!! Using a cut off Allen wrench in your drill motor (A round end in the head of the screw works best, as it will allow your drill motor to "float"), insert the Allen wrench into the head of the cap screw, and spin the beejesus out of the assembly, and I guarantee it will prime your LS motor with plenty of oil!! Wish I had pics and knew how to add them. This works great and costs VERY little to nothing. Good luck.

 

Interesting idea I will say, but that looks like the hard way to do it to me. I'll I did was pull the fuel pump relay and fuses and unplug the coil packs and use the starter to build oil pressure

 

When I replaced my oilpump/harmonic balancer and timing chain i first filled 8 oz of oil in this hole to fill the pump and oil system .
Then I removed the fuses for injectors before I run the starter for approx. 10 sec intervals .
On the second interval the oilpressure build up was OK . Shown on the HP tuner trend (upper white trend)

 

I packed the oil pump with Vaseline during install on 2 different builds and had instant oil pressure at startup.