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Cavitation at the pump resulting in aeration of the oil?<br>
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<div class="moz-cite-prefix">On 1/1/2020 12:16 PM, Michael MacLean
wrote:<br>
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<div dir="ltr" data-setdir="false">Well, then explain to me why
a Bugeye I had back in the 70s would read 60 PSI at speed when
the proper amount of oil was in the engine. At one quart low,
it would read 40 PSI at speed. Put in a quart and the
pressure would go right back up to 60 PSI. It amounted to a
rolling oil change with intermittent filter changes.</div>
<div dir="ltr" data-setdir="false">Mike MacLean<br>
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<div> On Wednesday, January 1, 2020, 11:24:06 AM PST, WILLIAM
B LAWRENCE <a class="moz-txt-link-rfc2396E" href="mailto:ynotink@msn.com"><ynotink@msn.com></a> wrote: </div>
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Oil pumps, vane, rotary and gear type are all positive
displacement devices, meaning that they will continue
to build pressure against resistance to the point
where something breaks. That is why they are all
equipped with a bypass valve which limits the amount
of pressure in the system. The amount of stress on the
geardtrain is directly proportional to the pressure
developed. I'm not sure if the problems related to the
rotary type pumps is a result of the stress of driving
the pump or to the larger pressure pulses (vibration)
that are inherent in the design. </div>
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The manufacturer selects the bypass valve and spring
assembly that will keep the pressure within a safe
range while protecting the drive system from over
stress. The four cylinder engines are supposed to run
at a maximum of 50-55 PSI, the sixes somewhat lower,
and it is the bypass valve that maintains that
pressure even though the pump itself is capable of
much higher pressures if it encounters excessive
resistance. </div>
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Viscosity change in the oil when at higher
temperatures will reduce pressure by reducing the
resistance of the oil circulating through the various
clearances in the engine. As the engine wears these
clearances will increase thus reducing resistance and
dropping oil pressure. Oil pressure alone is not as
important as is a constant flow of oil to all
components combined with the film strength of a good
quality oil. </div>
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Bill Lawrence</div>
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BN1 #554</div>
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<div dir="ltr" id="yiv5245057248divRplyFwdMsg"><font
style="font-size:11pt;" face="Calibri, sans-serif"
color="#000000"><b>From:</b> Healeys
<a class="moz-txt-link-rfc2396E" href="mailto:healeys-bounces@autox.team.net"><healeys-bounces@autox.team.net></a> on behalf
of Kees Oudesluijs <a class="moz-txt-link-rfc2396E" href="mailto:coudesluijs@chello.nl"><coudesluijs@chello.nl></a><br
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<b>Sent:</b> Wednesday, January 1, 2020 6:37 PM<br
clear="none">
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:healeys@autox.team.net">healeys@autox.team.net</a>
<a class="moz-txt-link-rfc2396E" href="mailto:healeys@autox.team.net"><healeys@autox.team.net></a><br clear="none">
<b>Subject:</b> Re: [Healeys] Oil Pumps</font>
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<div class="yiv5245057248yqt6284778669"
id="yiv5245057248yqtfd08562">Absolutely correct.
There may be theoretically a tiny difference,
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immeasurable probably, caused by the efficiency of
the various pumps.<br clear="none">
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Kees Oudesluijs<br clear="none">
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Op 1-1-2020 om 19:24 schreef Bob Spidell:<br
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> I'm not a fluid dynamicist, but wouldn't,
say, 45psi from either a <br clear="none">
> vane/rotor type pump put the same load on the
cam gear and driveshaft <br clear="none">
> as 45psi from a gear-type pump, all other
factors--oil viscosity, <br clear="none">
> etc.--being equal? Or, is there some other
factor(s) at play? Do the <br clear="none">
> gear-type pumps produce lower pressure (seems
to me that's the only <br clear="none">
> way they'd reduce the load on the gears and
the cam thrust plate)?<br clear="none">
><br clear="none">
> Bob</div>
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