Mike,
Perhaps the cup at the end of the spring is worn or scored. Is it perhaps
not seating properly or hanging up when warm?
Rule of thumb I have heard from relaiable sources is 10lbs/1000 RPM. You're
probably OK, but it _is_ unusual for A-series to run that low, especially
on a fresh engine,
Gerard
At 11:39 AM -0700 9/17/01, Mike MacLean wrote:
>I have been following the recent posts about oil pressure with
>interest. I have been chasing an oil pressure problem recently with my
>948 that is at the 2500 mile mark after it's rebuild. From a fresh
>rebuild the oil pressure would be a little over 60 psi cold and 20 psi
>at idle. After warm up it used to drop to 50 psi or less and about 15
>psi at idle. About 2 weeks ago I noticed the oil pressure cold was
>still 60/20 psi but after it warmed up it would drop to just a little
>over 40 psi and 10 psi at idle! Peter C. on the list sent me a correct
>spring for the oil pressure relief valve and I put it in this weekend.
>The cold oil pressure rose to 70/40 psi ! After warming up the engine
>with about 20 minutes of driving around town the oil pressure dropped to
>50/15 psi again. After another 15 minutes or so of driving the oil
>pressure dropped further to 45/10 psi. Over the weekend I tried to
>chase this pressure loss down and Plastigaged the middle main bearing
>and found it to be perfect at .0015 running clearance. I observed the
>rocker assembly with the valve cover off and could run the motor for a
>few minutes before the area below the rockers filled with oil. The oil
>was migrating away from the rocker bushed slowly, so that looked fine.
>There are only a few places in the engine to build oil pressure. The
>main and rod bearings, the rocker bushes and the oil filter bypass
>relief valve. Why is my pressure so good at cold and drop so
>dramatically when warmed up. As part of my effort to improve oil
>pressure I changed the 20/50 oil with a straight Castrol 40 wt as
>recommended to me by my friend that has rebuilt Healey motors for over
>30 years. He says he runs straight 40 wt in all his Healeys, big and
>small. What's going on here?
>Mike MacLean Supercharged 60 Sprite
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