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

[AlfaNeely@domain.elided]

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 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.
	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.
	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.
	 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.

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