For what it's worth many cars have used a similar system like Porsche (944s and
others). They did have a "fix" after many locked up resulting in no pressure.
The piston looks almost identical to the Healey valves.
________________________________
From: Chris Dimmock <austin.healey@gmail.com>
To: Joe and Lenore Armour <sebring@illawarra.hotkey.net.au>
Cc: Healey <healeys@autox.team.net>
Sent: Fri, October 1, 2010 11:07:12 AM
Subject: Re: [Healeys] [Fwd: Oil Pressure Control]
Ok. I'll post my oil pressure figures. With a bled valve.
The black and white car is due for an oil nad filter change anyway.
Weather permitting.
Me
Sent from my iPhone
On 01/10/2010, at 4:04 PM, Joe and Lenore Armour
<sebring@illawarra.hotkey.net.au> wrote:
> FWIW I have never been able to accept that the crude Healey (all BMC for
>that
>matter) 'pressure relief' valve, opens and closes that many times per second
>to
>manage the oil pressure we see at the gauge. The seat and valve are too poor a
>fit to be a positive seal and it does not remain shut until a certain
>pressure
>is reached. The volume of oil that flows thro a restriction, ie bearings and
>spray holes etc varies with tempreture, engine speed and general condition and
>bearing clearences.
>
> May I suggest that our 'relief valves' are flow control valves and apart from
>when the engine is stopped, the valve is never in the closed position and thus
>providing a positive shut-off. The spring/valve manages pressure by
>controlling
>the volume of oil allowed to by-pass into the sump.If you inspect a valve it
>usually is a loose fit in the bore and shows signs of having wear on opposite
>sides at the two ends, an indication that it spends most of its life rocking
>back and foward in its bore. Usually most of the oil supplied from the pump
>should be far in excess of the volume that can circulate thro the engine and
>therefore is continuously being by-passed back into the sump (pan).
>
> Most hydraulic system start-ups require ALL air to be bled before
>commissioning.
>
> Therefore it is most likely the weak spring tension that is allowing too much
>oil to by-pass when pressures are insufficient with the engine in GOOD
>condition
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