That's a good point Mark, I think I once calculated a surface speed of 49
feet per second so the alignment is pretty brief.
I may be all wet (oily?) on this one but it is hard to imaging the hole
alignment at BDC being critical as the crank is moving so fast the
alignment is quite brief. I would go with the groove as the main effect.
Mark Weathers
----- Original Message -----
From: <Gt6steve@aol.com>
To: <FOT@autox.team.net>
Sent: Saturday, June 26, 2004 6:36 PM
Subject: More oil
> Greetings Amici,
> 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
simple
> drilling error in the oil passage, That notwithstanding let's ponder some
theory.
>
> 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 in
> 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 was
> 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.
>
> Steve
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