I was not happy with low oil pressure on my M30 after a rebuild in 2014. My motor is a 3.5 from late 80's. Probably less than a 150k on it.
After rebuild with new bearings all around and a rebuilt B35 head it still ran around 20-25 at idle when fully warmed up.
While I had the engine out for the recent complete body restoration I wanted to do a couple more things to the motor like powder coat the oil pan.
The old while you are in there comes up. Oh yeah, low oil pressure.
I did some investigating and asking some other engine guys and since new oil pumps are NLA I determined that I could replace some parts that were still available.
I took my existing pump to my friendly machinist and we went over all the tolerances in the pump and all seemed to be reasonable. One thing I did notice was a fair amount of wear on a plate that is next to the rotor pieces that are the actual pump. There is a flat plate called an intermediate plate. For $3.00 I replaced that with a new one.
Now I have 40 PSI at idle on a warm motor and 70-80 at speed.
Number 9, number 9, number 9.......... Oh sorry that was the Beatles song.
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