Oil pressure relief valve plunger stuck, oil pressure up/down

[oc63rag]

I've done some searches and haven't found the exact issue I'm experiencing. 1600 DP, mostly stock (electronic ignition, header/exhaust, 30 Pict 1). It's been running great for years with no issues. I've got a VDO gauge for both oil temp and oil pressure. The temp runs about 160 on the freeway and around 130 on surface streets. The oil level is full. The pressure normally runs about 50 psi when cold, about 40 psi when warm and cruising about 45 mph and about 30 psi when warm and idling.
Yesterday the pressure jumped up to about 60+ psi when I started it in the morning. I drove it for about 20 mins and the pressure would move up and down with the rpm's and would drop to about 10 psi at idle once it warmed up.
I realize the pressure will fluctuate with the rpm's but this is drastically different from what it's done in the past.
This morning I pulled the relief valve plug and spring and the piston was stuck in the bore. I was able to remove it with that special tool (very handy, by the way). I cleaned the sides of the piston and made sure there were no scratches or anything.
I reassembled everything and made sure the piston would slide up/down easily.
When I drove it, it did the same thing as before with the swing in pressure from 60 psi to 10 psi.
I'll check the relief valve again in the morning but does that make sense? If the piston is stuck would it cause these issues? My understanding of the system is this should cause the pressure to be higher, no?
Thanks for any help.
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[Matt Wilson]

If I recall, the general rule is 10psi per 1000 RPM once warm. 60 on cold start and gradually decrease to 10, and fluctuations when driving would be normal in my experience. Sometimes gauges make people worry more than they need to.

Your driving temps seem a little cool - where is the sensor in the system?

Maybe something was plugging/obstructing the system and it finally pushed it self free??
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1972 Standard Beetle
1969 Baja Beetle

[oc63rag]

[Matt Wilson]

I think the pressure numbers you exhibit today are pretty normal. I've used a similar setup as this - the thing you have to be careful with here is the electrical connections for the pressure sender. Make sure they are tight and the terminals aren't accidentally contacting each other or something else that would mess up the gauge reading.
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1972 Standard Beetle
1969 Baja Beetle

[oc63rag]

[johnpded]

I have a similar but different problem. I had my 1600 dual port rebuilt 4600 miles ago and since that time my oil pressure has been at 60 on start up and as temp climbs so does my oil pressure. At times the temp is at 210 to 250 and oil pressure is at 75 to 100. My mechanic who rebuilt it doesn't seem to have a problem with those numbers. I am currently experiencing a problem with the way it is running also. It seems to be skipping and has a loss of power. I found a plug wire off, put it back on but still is not running correctly. Over the weekend i changed both plungers and the pressure is at 50 at start up but still creeped up as temp climbed. I to have a similar sensor setup. I also have oil leaks at my push rod tubes. Do you recommend the spring loaded replacement tubes?

[Matt Wilson]

Sounds like you may have some ignition and general tune-up stuff you could do. I've used the removable pushrod tubes, they can work well. Make sure the sealing surfaces are in good shape and clean.
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1972 Standard Beetle
1969 Baja Beetle