Everything in the paper is based on physics and not on using whale oil or unicorn piss to lubricate an engine. Bearing speed, mechanical oil consumption based on clearances, and film thickness are all discussed. There is a meaningful discussion in the appendix too. Nothing is presented as fact, only findings and observations. What I find funny is that so many people will dismiss findings from decades ago on the mere premise that it's 'old' data - but it doesn't matter when it was documented if it's based on things which don't change.
What I often find is that there's nothing new under the sun. What we use today is a result of research done back at the turn of the 19th century, we just do it better and more repeatable today but it's the same physics as they had back then. We also benefit from economies of scale which are able to produce far more complex junk at a faster rate than ever before.
What the paper basically talks about is that pressure fed from the crank journals to the rod journals experiences several forces and phenomenon which are repeatable and should inform a best practices approach to a lubrication system. First is that as engine speed increases, oil consumption at the bearings increases. There's also less time for oil to find its way from the crank journal to the rod journal which can lead to a lack of oil available in the passageway from the main to the rod. The oil in that passage is under immense pressure caused by the rotation of the crank (centrifugal effects), but if the rod clearance is excessive (side clearance was found to have zero effect, even back in 1927) then the oil gets 'consumed' too quick and runs out before it can be replenished by the mains. Larger mains clearances can increase the oil flow from the mains to the rods by an order of magnitude (!!!), and this is where grooved bearings come in, even back then. Wider, deeper grooves are always better from an oiling standpoint. Now, we're talking 2800 rpm as the 'high rev' range of these engines, so it's not like anyone is going to recommend leaving .05" wide margins on the mains of a 12k rpm prostocker or anything - but it does show where additional rod oiling can be gained and demonstrates the concepts clearly. Concepts still in use because of course they are.
Speaking of centrifugal effects on the oil for the rod journal - imagine what happens when stroke is increased? It doesn't make things better. This suggests that those of us with strokers really ought to pay more attention to oil feed and supply..
They even tested a re-routed passage from the main to the rod journal and effectively 'reversed the course' of the passage. Guess what? It reduced oil pressure and flow at the rod (duh). Which is neat because at least they demonstrated the effect physically, it's not just a theory.
Worth noting in the discussion toward the end was that the centrifugal effects also basically helped 'centrifuge' the dirt/debris out of the oil. That when oil passages were drilled blind into the rod throw, then cross-drilled from the rod journal - there was dirt and other debris found packed into the end of the blind passage - a small passage drilled through allows that trash to be ejected in a desirable direction so that it can find it's way back to the sump and get filtered and prolong engine life. Neat stuff!
Another observation was that if the oil feed from the main to the rod happens to intersect the rod journal surface where the connecting rod aligns near TDC, the oil flow is severely restricted because the pressure acting down on the rod effectively occludes the oil passage and oil film can break down and despite adequate flow the bearing can still fail. This wasn't the main topic of the paper and they refer to another paper where bright light and photography was used to directly observe a translucent gap at the bearing in order to track the existence of an oil film. Neat stuff again.
Timing was discussed briefly, and more-or-less it was found that by having oil supply at the mains aligned with the rod journal passage prior to TDC but some time after BDC, the oiling system has less trouble keeping the rod journal full of oil. Which to me, is the big take away and explains what YR is on about with the oil distribution canister concept.
What YR describes is a system which allows filtered oil to reach the mains in an area where it's advantageous for multiple reasons:
- Oil pressure entering under the crank is going to resist downward forces from the pistons more readily. This can help prevent film breakdown due to loading.
- Oil pressure entering near the rod journal passage while the piston is on the up-stroke allows oil to reach the rod journal as the load on the rod journal is increasing. This helps reduce the chance for the oil film to reduce at a critical time.
What YR describes is obviously meant for a max-effort type build, not just mom's grocery getter. However, the criticality of the oil system increases as stroke increases and as rpm increases. Those who really want to try and make power in the upper rpm range should not take oil timing lightly. The better the oil system performs at high rpms, the more power can be made 'up there' before the engine grenades. I'd be willing to bet that stock blocks are actually stronger than popular opinion would lead us to believe, but that oil system breakdown leads to catastrophic failure that gets pegged on 'weak blocks' instead of on poor oil flow management.
Looking around at some high effort blocks that used to be available, I see pictures of blocks with no oil pump provisions (built for dry sump) with oil holes tapped into the main caps. So for those that think this is all just chest puffing and fabrication for the sake of self-pleasure, I don't think you're fully grasping what 'max effort' means.
