the differance in oil pump primers is that oil pump primer drives that look like this won,t seal both oil passages in the block LIKE THE LOWER DISTRIBUTOR BODY IS DESIGNED TO DO!

you need to use the CORRECT TYPE THAT LOOKS LIKE THIS



look at the oil passage lay out

now look at the distributor lower end, it forms one side of one of the main oil passages when installed in the block, without it that passage can,t build pressure so no oil flows past that opoint under pressure without the distributor in place!

those two oil rings on the lower body seal the oil passage, on a stock chevy distributor they allow it to leak so some oil flows to the cam/distributor gears,
bottom of a Chevrolet distributor housing can be modified to spray pressurized oil onto the distributor drive gear. The extra lubrication will reduce distributor gear and camshaft gear wear. This is especially important when the gear is used to drive non-standard accessories, such as a high volume oil pump, or a magneto that puts additional loads on it and the cam. When the distributor is installed, the bands at the bottom of the housing are designed to complete the internal right side lifter galley on all small and big block Chevrolet V-8’s and 90° V-6 engines. If you hand file a small vertical groove .030" wide x .030"( thats the diam. that crane recommends on the bottom band (above the gear), pressurized oil running between the two bands will be directed downward onto both the gear and the cam. This procedure is recommended for all Chevrolet engines no matter what material gear (cast or bronze) or what type of camshaft (cast or steel) you are using keep in mind the groove MUST be lined up with the cam gear when the distrib. is installed