In true List protocol, I am going to jump in a with a related subject and
probably further confuse the issue-
There has been some discussion recently of brake pressure switches, and the
same principal applies here, but you would want the opposite result- that is
no air pocket to compress and either slow the operation of the switch, or
compress enough to not allow a stiff switch to operate. So , a good
practice is it to try and fill the switch with oil as much as possible
before installation.
Dallas
----- Original Message -----
From: "BJ8 Healeys" <sbyers@ec.rr.com>
To: <healeys@autox.team.net>
Sent: Thursday, October 07, 2010 9:27 AM
Subject: [Healeys] Thread on oil pressure relief valve
> Hello, Healeyphiles -
>
> Before the thread on the oil pressure relief valve gets too cold, I wanted
> to provide some information I received via communication with an
> instrument
> engineer at Autometer (http://www.autometer.com) concerning the function
> of
> the restrictor hole in the oil gauge line and the advisability of
> "bleeding"
> the air out of the line.
> While this is unlikely to put this issue to bed for all time, I thought it
> would be helpful to have the input from someone who is actually in the
> business of designing instruments.
>
> According to the engineer, restrictor holes are normally built into
> high-pressure sensing gauges to prevent damage due to dumping pressure
> into
> them all at once. For the restrictor in the relatively low-pressure oil
> line on Healeys, he says it would help to prevent the gauge from
> registering
> varying oil pressures from the pump at low engine rpms. As far as the
> need
> to bleed air out of the line, he says it is not necessary. As a matter of
> fact, the line will "re-air" itself each time the engine is shut down due
> to
> drain-back of the oil into the engine. Combined with the lack of vacuum
> relief, the restrictor hole will help to slow down the drain-back, but if
> the car sits long enough some oil will drain and will be replaced with
> air.
> At higher engine rpms, any air in the line acts just as a shock absorber
> and
> will dampen pressure pulses from the pump.
>
> Happy Healeying!
> Steve Byers
> HBJ8L/36666
> BJ8 Registry
> Havelock, NC USA
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