Also relevant to the scheme of things is the "packing" inside the relief
valve cap. Moss shows this part as 460-165 "Packing, oil release valve".
Its essentially just a metal spacer, maybe 1/8" thick, but it presence or
absence will have an effect on the spring compression. If you are missing
that piece and/or your spring has weakened, that would account for some
lower oil pressure reading symptoms. I know this because I lost or left out
this packing piece when I assembled my engine and it did cause lower oil
pressure readings. However replacing that piece plus a new valve and oil
pressure relief spring on my new engine gave me great oil pressure on the
high end but idle pressure is still a bit low.
Keep in mind that the spring will already be compressed considerable when
it is installed. You will know what I mean when you try to install it.
David Councill
67 BGT
72 B
At 09:20 PM 3/29/2004 -0600, you wrote:
>I removed the old pressure relief valve and spring tonight. The spring is 2
>7/8" long. http://www.pokrefke.com/mgb/springlength.jpg According to
>Haynes, the free length should be 3 inches, so I'm a little short.
>
>The relief valve was in fair shape. There was some erosion on the valve
>face, and the side had an odd wear pattern in one location.
>http://www.pokrefke.com/mgb/reliefvalve.jpg All things considered I think it
>was fine, but it will be replaced while I'm here.
>
>I was able to compress the spring to 2" by squeezing it between my thumb and
>index finger. Haynes says the oil pressure release valve opens @ 70lbs/in2.
>The spring is 1/2" in diameter, and according to my father (an engineer),
>this translates to a force of 13.7 pounds. I set a half-full 5lb bag of
>flour on the spring, and it compressed approximately 1/8". 2.5lbs on the
>face of the spring is equal to ~13 lbs/in2.
>
>My theory is that while driving, the oil pump produces enough pressure to
>give me the 10psi/1,000rpm, but while idling with a sump of hot oil, the
>pressure valve was opening around 10-13lbs/in2.
>
>I won't be able to get her put back together for about 10 days. I'll let
>you know if I was correct.
>
>Thomas James Pokrefke, III
>1970 MGB
>pokrefke1@comcast.net
>http://www.pokrefke.com
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