Re: Restrictors in the oil passages

[bearbvd@domain.elided (Greg Hermann)]

>The modification which Russ Neely mentioned that his friend did at the
>suggestion of a well known Alfa mechanic - restricting the oil flow to the
>cams in order to maintain pressure down below - is a new one on me.

Me too.
>
>I will admit that I can't recall having heard of great problems with camshaft
>bearing wear, but I have seen (and heard of) badly worn cam lobes and badly
>scuffed cam cups, and had assumed that they got their lubrication by a fairly
>substantial flow-through from the cam journals.

The lobes and followers are bath lubed--all the outwash from the cam
bearings does is replenish this, but I have a hard time believing that a
difference in flow rate which is pretty low compared to the size of the
bath would make even 5 degrees difference in the temp of the oil bath. In
fact--I suspect that thinner oil up here migh help a bit. Any cam with more
than about 10.5 mm of lift will lead to geometrically shorter lobe/tappet
life. Never tried synthetic oil, this might well help, especially an ester
based one with really high film strength!
>
>Using the allen screws, and then drilling them to get the desired
>flow-reduction seems odd. I have seen references to reducing coolant flow by
>plugging water holes with threaded aluminum rods and then drilling; the CRH
>says suitable "allen head set screws can be used if they are aluminum", but a
>friend did this sort of thing on his GTA with heliarc welding.

In this more modern day, I suspect that ceramic coating on the chambers and
parts would accomplish far more positive in the HP department than
restricting water flow ever did, and would also do a far better job of it,
and leave you with a far more durable engine (more even temperatures
because of higher water flow)!!
>
>I have just flipped through the CRH to see if I could find any historic
>observations about the head gaskets, O-rings, cam lubrication and all that.
>Didn't find it, will have to ask some of the Seniors. In the section of notes
>on Sebring follow-up (GTA) I noted that 7500 was the recommended max RPM

A fuzz low, but not unreasonable.

and
>oil pressure was given as 40 normal, 30 minimum, which I couldn't help
>relating to the "keeping the oil pressure down in the bottom of the engine
>will help late in a race when the oil gets thin" mentioned in the
>passage-plugging explanation.

Did any of these guys ever figure out that the REAL answer is to set up the
crank main journals so that their clearance is .0023"--.0025" AT OPERATING
TEMPERATURE?? (This translates to .001"--.0012" at room temperature.) (It
also translates into fairly careful warmups, but you will NEVER have
another oil pressure deficiency if you do it this way!! (The aluminium
block expands more than the steel crank as things warm up, thus increasing
the main bearing clearance at operating temp SIGNIFICANTLY above what you
would measure at room temp!!!)
>
>The CRH is perennially interesting reading. At the bottom of Group 1 Page 1
>there is a lovely section on valve train balancing - the camshafts must be
>balanced, and the cam sprockets must be balanced separately (and dynamically)
>while allowing for sprocket lock bolt weight, and everything else - heady
>stuff.

This strikes me as unadulterated and totally unnecessary B.S.!!! Did they
recommend checking the sponson rods and grease the muffler bearings
regularly too?? Or were those not profit center operations for their shop??
For starts--the cams turn at 1/2 engine speed, to continue, there isn't a
part of the cams far enough from their centerline to generate any really
significant imbalance force!!
>
Regards, Greg

------------------------------