Back in the day we ran half grove bearings- Vandervell etc because you loose a lot of bearing support with the grove- I think maybe 30%- you loose oil film near the edges of the bearing and half grove have twice as many edges as well as the groove
We found that quick and dirty cross drilling was not the answer
and some smart crank guys figured out oiling drillings that work much better
There is a graphic for inline which shows where you want to inject oil for best oil film- hydrodynamic wedge
when converting to V8 you have to consider both banks and the fact that two cylinders fire next to each other
one reason we grooved the blocks bearing bore with a tool that rotates with the main C/L but has a cutter on the eccentric- think like a crank throw with teeth
That puts the oil in the trough by the parting line and you do not loose oil where the big clearance is at the old oil feed location at the top- worst spot to feed a main
70 ATDC is closer to where the rod is tangent to the crank throw than 90 degrees close to where there is the most cylinder wall pressure
you get the most mechanical advantage at the tangent point
a long rod is at more degrees ATDC than a short rod another reason why each takes a different cam
