I agree with Craig,
Remember that we are dealing with fixed positive
displacement oil pumps. I believe the oil pressure
relief valve is set at 70 psi (from memory). So if we
ignore leakage in the pump itself, the volume of oil
pumped below 70 psi (or whatever it's value) is a
function of the RPM, not the pressure developed.
The pressure will be a function of viscosity, and the
bearing with the loosest clearance. The loosest one is
often the camshaft bearing(s). The loosest bearing
will also flow more oil, robbing flow to the other
bearings (remember fixed volume per RPM). And since
the amount of cooling by oil is a function of flow
volume, this then reduces cooling to the rest of the
bearings, etc.
As has been stated, oil foaming is *BAD*, but it is
usually caused by air at the pickup (too little oil)
or crankshaft thrashing (too much oil).
I would not rush out and tear down a street engine
solely because the oil pressure was low at idle. Mind
you, a rebuild is in your future, but you can plan for
it, instead of being forced into it.
Carter Shore
--- Craig Smith <CraigS@iewc.com> wrote:
>
> By what all the local racers say in my neck of the
> woods,
> " A pressure is what your after "
>
> As long as you have a pressure your good to go at
> idle.
> Running pressure is a little more important, an
> engine at high revs needs
> the circulation of the oil, one of the major reasons
> for oil in an engine is
> for cooling, of course the lubrication is part of it
> but with just
> lubrication and no cooling any engine will
> eventually get too hot.
>
> A major problem of high revving engines is oil
> foaming, foamed oil carries
> air, air is not good in a lubrication or cooling of
> an engine that is under
> a lot of stress. The racer on the list probably
> have oil pans customized to
> reduce the foaming of the oil.
>
> So all that junk said, a positive pressure is
> needed, a HIGH pressure is
> bad.
>
> Make sense ?
>
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