Re: alfa-digest V7 #630 - Restrictors in the oil passages

[bearbvd@domain.elided (Greg Hermann)]

>
> OK, on that part we totally agree. I know guys who have taken apart a lot
> of Alfa engines, and the cam bearings almost never suffer damage, roll
> pins or no roll pins. The cam bearings themselves provide most of the
> pressure drop in that path, as it should be.

Agreed!
>
> If you are fitting grooved bearing shells at #2 and #4 mains in a block
> drilled for direct oiling, do you also groove the main journal?

Not only no, but #%$ NO!! This would create a stress concentration in the
crank, and be VERY undesireable. The classic approach is to "cross-drill"
the crank--drill two holes at 90 degrees to each other clear through the
journals

Do you
> also plug the redundant crank passage, or leave it alone?

Would be inclined toward the latter, but careful study needed here.
>  >>
>
>	No, I have not had the crank cut for grooved mains or rods.  I really
>had not considered it, but it would increase the reserve of oil held at each
>bearing surface.

See above. Don't do it. rod journals may be cross drilled as well as
mains--increases the number of points where oil is applied to the bearing
when you cross drill the rod journals, improves the consistency of the oil
feed to the rods when you cross drill the mains.

 If the crank has to be ground and renitritrated, having the
>crank grooved is a possibility.

PLEASE--don't do it!1

 On my most recent engine, I did have the oil
>holes chamfered and a radius cut in the corners of each journal.

Chamfering works well. Pay attention to the direction of rotation when
doing it! Do it in such a way that the bearing going by the end of the oil
feed hole tends to draw oil aout of the hole.

Greg

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