STAGE 2 OILING
Austin, actually the individual lifter bores are drilled from the side above the cam. They are drilled from one side thru both sides so that the drill breaks thru into the oil gallery running parallel to the cam. The hole is recommended to be 1/8". You then tap the hole that's to the inner side, [closest to the C/L of the block[, and plug it w/ a allen set screw w/ loc tite on it.
This can be visualized as seeing the lifter bore as a beer can and you are drilling thru both sides and then plugging 1 back up!!
This is necessary only if the block you get was never drilled. Some were not as the rockers were fed thru the shaft [T&D] via an external oil line from either the ft or rear main pressure feed boss, to the end of the heads.[STAGE 2 heads ONLY]
The Jesel, paired rockers, were fed thru the p.rods, thus requiring the lifter drilling deal.
HTH, For a REAL explanation, w/ fotos, plse consult the BUICK Power Manual. All the details are there.
Happy Holidays to all!!
Back to takin BLACK BART apart!!

Damn, I just LOVE these 6 bangers!!

Actually, it's just time to add some more goodies!!