In a message dated 1/18/00 6:55:53 AM Pacific Standard Time,
STELLMAN@noex.com writes:
> I need some expert advice. I have a 350 4 bolt main that I personally
> rebuilt and installed in my truck. When I start it ,it has 60# + of oil
> pressure but when I drive it a few miles (4-5) and stop at a red light or
> something the oil pressure will drop to 0-10# when idling. As soon as I
> accelerate it will shoot up to 40# and settle back to 25-30# when cruising
> down the highway at 2000 rpm. It had a brand new Melling standard oil pump
> that I have already replaced with another Melling standard oil pump. I
have
> never used one of these before. In the past I have always used Chevy oil
> pumps and don't remember ever seeing this much pressure fluctuation and
> those low of readings. Does anybody have any ideas what could be wrong?
Is
> this normal for Melling oil pumps? Should I replace it with a Chevy pump?
> Could there be some other problem? I Plasticgaged the bearings when I
> assembled it and everything was on the minimum side of the tolerances.
Also
> I am running 10W40 oil. Any help or suggestions would be appreciated. I
> really am not looking forward to taking the engine out and completely
> rebuilding it again just to try and find this problem. TIA>
>
>
> Terry Stellman
> 1949 3600
> Missouri City, Texa
Terry,
As mentioned before, any excess clearnces will cause a low PSI when idling,
but assuming you put everthing together correctly, I'd first verify the
pressure with a known, good, mechanical gauge.
In my '57 with a BBC in it, I still have the original mechanical gauge in
it, and a SW electric gauge.
Even when the SW was new, the gauge(SW) would fluctuate erractically at
idle, while the mechanical original would stay steady. Also, the SW reads
about 8-10 PSI higher (by "eye-balling") than the original.
Mike
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