Low oil pressure after long high speed run

[gkent]

Bearing clearance doesnt affect pressure anywhere near what leaky lifter bores will.

That's a fact jack !!!

 

[dammstrate]

Thanks guys for the info. It normally idles and drives around town at ~50 psi. I have only seen the low pressure after that extended 4000 rpm run. I haven't had the car that long. Motor was supposely built by an "old school" guy. I will change oil and try some 20W-50 with some zinc for extra protection. Something like this:

 

[69hemibeep]

Maybe foaming the oil a bit at high RPM?

 

[j-c-c-62]

Maybe foaming the oil a bit at high RPM?

Good question.
However, based on OP, "Pressure gradually rose back up at each stop" the question then becomes, how gradual?
I would think hot thin oil at bottom of oil pan with a running/vibrating engine would not take long to de-foam at idle.

 

[RoasterStrudel]

I see there's plenty here about mechanical stuff, but...What are you using for a gauge? My stock gauge scared me with low oil pressure a couple times, turned out it was just the sending unit failing!

Just a simple thing to check before you start taking the big stuff apart.