Sudden oil pressure drop at idle

[dwdsm]

So I was out doing some pulls in the car driving it pretty hard and on return I noticed a 15psi drop in oil pressure at hot idle. The car has always idled at 30-35psi (going on 5 years now) hot and now suddenly it's between 15-18psi hot. I know it was high before and 15-18 at 950rpm is probally normal but the sudden drop scares me.
My balance shafts are deleted and the relief valve has been ported. I drained the oil and cut open the filter with no significant signs of metal. I was considering pulling the pan and oilfilter housing to see if the relief valve was stuck open.
Recently I put on a new valve cover so I'm sure some RTV made it's way to the pickup tube but I doubt enough to clog it. Plus high RPM pressure as always goes over 100psi.
Also just yesterday cut out the 2.25 resonators and welded in some 3" pipe (hence why I was doing some logging.)
Should I error on the side of caution and pull the pan?

 

[dwdsm]

I have to remove my down pipe anyhow to put on my new turbine housing so I'll pull the pan to see what's going on. Is a visual inspection good enough or should I plastigauge?

 

[99gst_racer]

What oil are you running?

I honestly don't know what to tell you about the sudden change, but 15-18 psi is just fine.
I would be more concerned with 100+ at high RPM. With a good ported OFH, my hot oil pressure is around 15-20 psi at idle and never goes beyond 85 psi at high RPM.

 

[dwdsm]

What oil are you running?

I honestly don't know what to tell you about the sudden change, but 15-18 psi is just fine.
I would be more concerned with 100+ at high RPM. With a good ported OFH, my hot oil pressure is around 15-20 psi at idle and never goes beyond 85 psi at high RPM.

1st off I admire your work, it's inspiring.
I run 10-30w full synthetic. I have been running heaver stuff to help my little leak on my main seal. Now that I have done a proper calan catch can setup I could go back to a lighter weight because that has cured my positive crank case pressure problem.
I have always been concerned with the high oil pressure but it's going on 5years and 40+ passes down the track. So I have no idea why it's so High. I made sure that the piston in the bypass valve was burr free and slid in silky smooth. JAM thinks the spring could have recently failed or the oil filter failed.

 

[dwdsm]

I fixed the little lope in the idle and changed the oil/filter and the pressure is back up. I just had switched to oem filters and that may have caused a drop as well as the idle lope. OK no bearings right now.. I am now going to switch to valvoline racing oil 5w-30. High zinc and it's 8.99 per quart so not too bad.

 

[97gst_spyder]

Brad Penn is just as good or better, $4.93 a qt.

 

[dwdsm]

Brad Penn is just as good or better, $4.93 a qt.

Where can I get it at that price?