this part drawn is the first part you find just below the lifter retainer clip, it falls out of the lifter housing first as soon as you take off the clip.
machine a groove up to the hole approx .010'' deep to increase oil delivery to the rockers up top.
i studied the depth of the oil galleys along the interior of our stock roller & non roller lifter housings... i see that this hole spends **VERY LITTLE** time aligned with the interior of the lifter body oil galley. Since im measuring from the outside because i cant step in side there to see, i calculate that this hole will be getting oil once the lifter hits approx 50% up the cam lobe.
This could be interperted into degrees and once there, can be converted into "time",adding this groove allows the hole to be accepting oil as soon as the lifter hits the cam lobe which increases how much time its capable of lubrication delivery.
thoughts?
see below,
Given that pushrods and rocker arms almost never wear out on these engines I'd say it's an unnecessary mod. They don't get much oil because they don't need much oil. I'd be more worried about the lifters collapsing from lack of oil pressure because you're letting too much oil out of the lifter bore...
if you're that concerned about not enough oil up there you'd be better served by running a high quality Euro-spec synthetic oil. That way you can make the most of the little bit of oil that's there...