After all this discussion, I looked to find a graphic that would help
to explain this and I simply searched google for "Healey 3000 oil
pressure relief" and found this informative article:
http://www.carolinahealeys.com/Technical/Engine/oil%20pressure%20diagnostics.htm
So, for those that are still stumped: your homework assignment is to
read the above. Test on Monday.
Olin
On Oct 1, 2010, at 2:04 AM, Joe and Lenore Armour 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.
> I drove my BN.4 on my honeymoon with 15 psi on cold start up, 12 psi
> hot and used it as an every day work transport from Dec. to April
> when a re-build was in order.
>
> Are there any hydraulic engineers out there? I am just a simple
> working man.
>
> Joe
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