Oil pressure low in 427 C/O

[Eljaro]

I installed a brand new Melling HV pump, and the pressure is still very low. 10psi at idle hot and 40psi at 4000rpm.
Today I took out the oil filter adapter and there was this 1/4" hole which I had never bothered about or had never really seen, but which was mentioned as a possible cause by SFfiredog.
The gasket over the hole was blown
( that probably happened when I saw 90psi the first trime I fired up the engine after the rebuild, but never again thereafter), so the oil was pumping right back to the oilpan, reducing the oil pressure.
That is most likely the culprit. I bet that when I get the hole plugged I will get decent oil pressure.
I'll fix that this week and will probably get back with good news.
One thing that worries me though is that I did about 50 miles today with that low oil pressure. Even at 5000rpm the oil pressure never got above 40psi.
I hope I didn't ruin the bearings.
Thanks to SFfiredog, whose suggestion I did not consider initially, because I had never SEEN that hole. But there it was !!!

Nearly all 427 center oiler blocks have a small (1/4") hole under the oil filter adapter pad that should be plugged. I'm not sure what the hole was for but I believe it was for some drainback to the pan when FEs were used in undustrial applications. Normally, when using a passenger car adapter the hole is covered by the adapter and gasket. But in Cobra applications where a remote oil filter and/or cooler is used, nearly all of the adapters have an open area over the hole that is only covered by the gasket. If the gasket blows out or leaks, oil pressure will bypass internally right back into the pan. Depending on how bad the tear in the gasket is, this will result in low or no oil pressure at idle when warm. I'm not saying this is your problem, but I have seen it happen plenty of times and it is easy enough to check out and fix. See photo, an allen plug is installed in the hole.