All this recently talk is touching upon a subject dear to my own heart
lately. I've been suffering oiling issues that MAY likely boil down to a
drilling error in the oil passage, That notwithstanding let's ponder some
A race or two ago I observed the oil groove in the main bearings did not
entirely coincide with the main journal hole passing oil to the rods. I didn't
feel confident but I opened up the main journal holes to fully match the groove
and had no noticeable improvement. As I said, I think (hope) my problem was a
restriction in the block.
Putting in a freshly reground crank today I note that again, the rod journal
supply holes are poorly aligned with the supply groove in the main bearings so
I dutifully chamfer the holes to provide maximum coverage.
All good BUT, how much of the oiling is dependent upon the groove and HOW
MUCH is dependent upon the oil hole in the crank matching up with the oil hole
the block at Bottom Dead Center??
What I'm saying is, Is the primary critical oiling done when the crank is at
BDC and the clearance max, oil holes in alignment, lots of high pressure oil
flowing in, and the groove merely a support function. Or is the groove the
highly critical oil supply avenue.
It seems that the engineers made an effort to match the drillings so the
block high pressure drillings matched up with the transfer holes when the rod
at BDC or before. Thus, I tend to think the line up of the holes is an
important factor so how can I exploit this timing to improve my reliability.
This may be patently obvious to most, kindly help me work through this so I
can improve my understanding.