Grooving lifter bores
I can't help but wonder how many of the camshaft/lifter failures happened using the rod bearing shells without the squirt hole.. The squirt hole was to align with the cross drilled crank to get a straight shot of oil, timed, when the other end of the hole aligned with the cam bearing hole.. I was taught that was to squirt oil on the cylinder wall,, but I wonder how mucha the "overspray" would shoot at the cam lobes, and reduce the wear/failure,,.. just thinking out loud..
I've always used the squirt hole shell,, even if I have to mod the shells myself.. and never had a failure.. fwiw
jmo...
THIS!!!
Many times older engine parts like bearing shells get superseded by later specifications. In our case, replacement rod bearing inserts for LA engines are typically Magnum engine parts. While they may physically interchange, they are not always backwards compatible. The oiling hole/notch on the big end of rods went away a while back for a couple reasons. First, later roller cams don't need as much splash lubrication, and second, by removing the squirter, the oil load on the piston rings is reduced allowing for lower tension oil rings while still maintaining oil control. This is generally a good thing as tighter oil control not only extends catalyst life (think 100K mile warranty), but also reduces detonation, which in the age of spark-knock feedback ignition control translates into increased efficiency.
But here's the rub, when we reduce the amount of oil slinging around the crankcase, we run the risk of underlubricating our oil dependent flat tappet cams. I think this is a bigger factor in cam/lobe wear failures than the reduction in ZDDP levels in current oils (which have come back down to levels similar to the oils available in the 60's). ZDDP being an anti-scuff agent really does not come into play unless the oil film breaks down. The best insurance against oil film break down is plenty of clean cool oil! Whether this oil is delivered through a grooved lifter bore, oil hole in the lifter face (Crower) or a small flat on the side of the lifter (Rhoades), or notched rod bearings, it is important to long cam and lifter life (I won't even get into the soft crap many cam blanks are made from).
A few years back when I rebuilt the Buick 350 in my Jeep Gladiator, I had to cut the notches in the bearing shells myself (I also went to full groove mains). The commonly available replacement parts are late model 3800 V-6 bearings. Going down the highway at 3000+ RPM (4.10 gears) I have no doubt that everything gets plenty of oil. But since it is still a working/hunting/camping/fishing/expedition rig, I was far more concerned with the ability to idle for extended periods at low RPM and not have anything run dry. So far, so good after 35K of abuse.
Long story short, grooving lifter bores on a street engine will probably pay benefits. And, since most install the larger M72HV oil pump during rebuilds, there is plenty of oil delivery to support this (the stock pump would probably be adequate).