[Healeys] Thread on oil pressure relief valve

[Herbert Miller]

Something to think about.
The illustration of the gear type oil pump in my shop manual shows 7 teeth,
thus 7 cavities between the gears per revolution.
At 1000 rpm the pump gears rotate at 500 rpm, that's 3,500 pulses per min.
or almost 60 pulses per second. 
I do not think the gauge can respond to this frequency. Even if it could you
could not see it. Tell me you can see the flicker of an
Incandescent household light bulb.

Herb Miller

-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of BJ8 Healeys
Sent: Thursday, October 07, 2010 8:27 AM
To: healeys at autox.team.net
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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