Ira replied:
>Hey there Russ,
>
>Am I the "oil expert" you are refering to? If so, I appreciate the
Yup. (But don't let it go to your head. There are lots of experts on this
list - just ask them!) ;)
>You are correct that surface tension, viscosity, and
>probably dozens of other factors that only a physicist could
>understand
Whoa! I am one. But I don't do oil, and it's a mystery.
>
>Before you crank your engine, that thin film of oil will be there -
>sitting and protecting. 5 years, 10 years, most likely even longer -
>the oil will be there. However, crank that engine and that layer is
>almost instantly wiped / pushed / pulled away leaving your engine
>under-lubricated.
>
That's reasonable and, if there is any logic at all to the practice of
"priming the pump", it must be the answer (for lack of any alternative I
can think of). And, of course, there is the corroborating evidence that
engines run without oil will soon sieze up, so it's obvious they eliminate
oil from bearing surfaces when running.
But this means that any benefit of priming is lost unless the engine is
started immediately thereafter - otherwise the oil pressure will take about
as long to build up again as it did originally and the engine will be left
with only the same oil-coated parts it started with. The Bugeye (I think)
owner who mentioned running the starter before the ignition was turned on
accomplishes this perfectly. Ingition-off cranking can also be done on the
very early B's, and probably A's, by pressing the rubber cap on the back of
the solenoid. (Did you owners of 3-main-engined B's know that was there?
I found it by accident - "Gee, I wonder what this does" and the engine
cranked, in gear, of course.)
>OK Russ, OK guys and gals - does this answer the question?
>
Partially. There's still the issue of how much difference this all makes.
Let's accept the fact that idle bearings will remain well-oiled
indefinitely. Then the question becomes, is undo wear going to occur as a
result of all the oil being squeezed out by the engine running, with no
load, in the several seconds before the pressure builds up? I remember
reading several years ago that some organization had "determined" that a
hugh fraction - like 40% - of all engine wear occurs during startup. It
seemed to be an official proclimation but was undocumented and I was
skeptical. Anyone know of this?
Russ Wilson
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