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

[Simon Favre <simon@domain.elided>]

I think we're talking in different languages. ;=)

AlfaNeely@domain.elided wrote:
> 
> In a message dated 4/12/99 1:06:13 PM Central Daylight Time, simon@domain.elided
> writes:
> 
> << Subj:         Re: alfa-digest V7 #630 - Restrictors in the oil passages
>  Date:  4/12/99 1:06:13 PM Central Daylight Time
>  From:  simon@domain.elided (Simon Favre)
>  To:    AlfaNeely@domain.elided
>  CC:    alfa-digest@domain.elided
> 
>  AlfaNeely@domain.elided wrote:
>  >
>  > Simon,
>  >         I was not suggesting that everyone partly plug off the oil passages
>  > to the cam bearings and I am not sure I agree with it.   However, my friend
>  > HAS done this to 5 of the 6 bearings and his engine is alive and well in a
>  > racing environment.  Thus, all the concern about roll pins constricting oil
>  > flow to the cam bearings was, I felt, of no consequence.  That was the
> point
>  > I was trying to make: roll pins are not going to limit oil flow enough to
>  > matter.
> 
>  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.
> 
>  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? Do you
>  also plug the redundant crank passage, or leave it alone?
>   >>
> 
>         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.  If the crank has to be ground and renitritrated, having the
> crank grooved is a possibility.  On my most recent engine, I did have the oil
> holes chamfered and a radius cut in the corners of each journal.

I was not suggesting grinding grooves in the crank. I was talking about the
bores in the block, but that may be a useless idea.

>         I am not sure what you mean by a "redundant" oil passage.  The four
> cylinder Alfa crank is drilled with six holes capped by the infamous aluminum
> plugs.  One hole goes from the number 1 rod bearing throw to the number 1
> main.  The second goes from the number 1 rod through main number 2 and stops
> in the middle of rod bearing number 2.  The third goes from number 2 rod to
> number 3 main.  The rest of the crank is a mirror image of the front half and
> I will ignore it for this discussion.

If you have oil coming into #2 and #4 mains from the new holes in the block 
via the drilled bearing shells, then perhaps the oil passages in the crank
that fed #2 and #4 are redundant. It depends on your point of view, I guess. 
;=)

>         I said the holes go in a certain direction as that is the way they
> were drilled at the factory.  However oil goes from number 1 main through the
> hole to number 1 rod and BACK against centrifugal force to main number 2.  Or
> it comes from main number 3 out to rod 2 and BACK to main 2.  Main number 2
> gets its oil only if the oil pressure is great enough to overcome centrifugal
> force and come back to the main.  The oil pressure at main number 2 has got
> to be less than the pressure at #1 or #3, which are fed from the oil galley.
> This is also why every Alfa I have ever seen with a spun main bearing was
> either #2 or #4.

Except when the oil pressure was 0 and it spun them all...

>         With the block drilled from the main oil galley to main bearings #2
> and #4, all mains get the same oil pressure.  Oil can flow to rod bearing
> number 1 from either main number 1 or through what I think you are calling a
> "redundant" oil passage from main number 2.  Rod number 2 now gets oil from
> either main #2 or #3, et cetera.
>         Of course, the bearings for mains number 2 and 4 have to be drilled
> to uncover the new oil supply hole.  And I like to search for a fully grooved
> main bearing set.

This is where I was trying to ask a question. I guess I was confused about
the shape of the bearing shell. If the grooved shells don't require a groove
in the block bore, then it sounds like a viable option. Is grooving standard
shells an option?

>          The block is drilled from the driver's side.  On the Bosch 2000 the
> hole for number 2 main can be drilled through the oil pressure sender hole or
> just below it.  The 74 2000 in my garage has a boss cast in the same
> location, but is not drilled for an oil pressure sender.  The 1600 I have
> would require some study as the oil filter is right where you want to drill.
> Perhaps the 1600 could be drilled from the passenger side the same as the
> factory holes are drilled.  All three blocks I checked have a boss in exactly
> the location desired to drill main number 4 and plug with a set screw.  I did
> not check the 1300 and 1750 blocks in my shed.
>         I DO recommend this modification for any Alfa four cylinder.  Street
> cars can spin bearings just as a racer can.  The same friend who plugged the
> head oil passages drilled his own with a hand drill and a very steady hand.
> I send mine out and pay the $100.
>       As is mentioned in Pat Braden's Alfa Bible, I also have the aluminum
> plugs in the crankshaft drilled and tapped for set screws.  This is not an
> easy task on the nitratrated late model cranks and at least one machine shop
> is no longer willing to do it.  I sent my last crank to Jack Beck at Orion
> Engineering (402) 331-5913 in Lincoln, Nebraska.  Cost was about another $100
> plus shipping.
>         Simon, I am sure you know all this.  I have gone into more detail for
> others that may read this.

It's definitely more interesting than cupholders.

Ciao,

Simon

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End of alfa-digest V7 #636
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