I have an old dizzy with only the shaft and I ground the top end to a 6 sided ordeal so my cordless drill grabs it easier.
I spend time on other forums. Over the years, I've lost track of the number of folks who post about burning-up 3/8 drills, especially cordless.
You're NUTS to use a cordless or 3/8 drill to turn an oil pump priming tool. The tool is spinning an oil pump that is geared to turn at 1/2 crankshaft speed. The engine develops plenty of pressure at cranking RPM--probably under 200 rpm.
You can prime just fine spinning the pump 60--80 RPM. About one turn per second. The oil is cold and thick, so it doesn't flow all that well.
And then someone puts a low-torque drill that's likely geared to spin 2000 rpm, but with little torque onto the end of the priming tool. Of course the drill burns up.
AT LEAST use a 1/2" drill, geared for 500 rpm, and four times the torque.
Better still, turn the pump BY HAND. For Chevy and Pontiac, take an old Points distributor, grind the teeth off the distributor gear. Thread a long machine screw into the top where the rotor used to screw on, and if you wanna be fancy, use a few inches of brake tubing over the threads of the machine screw as a handle. Works on any engine with a SUBMERGED oil pump driven by the distributor. (You may need a drill motor for Buick, Cadillac, Mopar B and RB, etc, where the oil pump is above the level of the oil, and must suck mightily to prime.) Oldsmobile is even easier--use a 5/16 socket to grab the oil pump driveshaft, and spin it with an extension on a ratchet or speeder handle. Ford with the hex driveshaft is probably similar.
But what about priming the valve train?
What about it? Priming the oil system takes less than one minute. The ONLY thing you're trying to accomplish is filling the oil pump, oil filter, and
main oil galleries with oil. The galleries will begin to drain immediately after the priming has stopped.
Some guys make a career out of "priming" the pump, turn the crankshaft, prime some more, turn the crankshaft, prime some more...all in the hope of squirting oil over the fenders from the rocker arms. I've seen posts where guys spend HOURS dicking with the oil pump priming tool. THIS IS CRAZY.
Every moving part in a new engine should be coated in assembly lube.
"Priming" doesn't lubricate anything--it just displaces air. And hydraulic lifters are notorious for needing to be bumped by the camshaft before they'll properly fill and pass oil up the pushrods.
"Over-priming" to get oil at the rockers is another reason drills burn up.
Priming is DONE when you see oil pressure on the gauge. Shove in the distributor, and fire that mother up.
With a submerged oil pump, "priming" the oil system is MOSTLY just a "feel-good" deal. It really doesn't do anything useful, because even without priming, the oil system will fill within five seconds of the engine starting and running. In the meantime, all the parts are sliding on the assembly lube, no harm done.