Oil pressure goes way high @ idle, then drops???

OK, so this is what I did, and this is what I have. 65 Mercury with a 390 2 bbl. Carb needed rebuilt, water pump went bad, soooo picked up a reman Holley 4bbl, (600 cfm), a used Performer intake, and a new waterpump. Put everything back together, car starts in about 30 secs. of cranking. So far so good. Warm the car up to set the timing, notice the oil pressure climbs from about 50 @ 700 idle, to pegging the gauge! Turn it off, start the engine, oil pressure is back to normal for a minute or 2 then pegs again. Using Mobil Delvac 10-40 and a K&N filter, 6 qts. Before the changes oil pressure was about 40 or so at a 500 idle. The engine has about 87k, doesn't leak oil from anywhere so far, but the idle lopes a little, suspect a vacuum leak, another new symptom. Anyway, I'm looking for some guidance and I appreciate the help.

electric or oil tube type gauge?

It is the stock electric gauge, which I know isn't the most reliable but since I changed a bunch of stuff I'm assuming it's something I did vs. the gauge. That said, I call this car Golden Gate, since I started fixing from the front, move to the back and repeat, just like the painters of the bridge!

what kind of fuel pump are you running. also what does the oil look and smell like.

Stock mech. pump, same one used before the upgrades, and the oil and filter are fresh.

Why 6 quarts?

FE's originally used 5, but suffered oil starvation problems due to excessive oil being sent to the lifters. Somewhere in the early 60's dipsticks were replaced allowing for 6 qts to read correctly. All later FE's used 6. This of course assumes 5 +1, (filter being 1).

While I am not really a Ford guy I have owned a few. One was a 1976 Ford F250 4x4, these trucks were the first of the Factory High Boy trucks. Came with a factory lift kit and such. This truck was equiped aith a 390 and it only had less than a 1,000 miles on it when one day driving down the freeway I toasted the motor. No warning no nothing, I wasn't paying any attention to the oil pressure gauge ( Factory one) it just quit. Got out and noticed there was oil every where. Had it towed back to the dealer and they fixed it under warranty, installed a new replacement engine. Two weeks later almost the same thing happened again, this time I noticed all of the smoke and got it stopped. Crawled under there and the oil filter was just hanging there, walked and got a new filter and oil and everything was cool until a week later and it blew another filter off. Now the explanation I got from Ford was that the check Valve was sticking and oil pressure built up very high and blew the filter. Ford replaced something ( Check Valve??) and it never happened again.

Now I don't know but could this maybe what you have going on?

RS

Good news is that makes some sense to me, bad news is that I believe on the FE it is in the oil pump. I'll dig through the shop manual and see what I can find. Thanks!

Just my 2 cents. First, I never heard of the 5+1 on the oil deal. The only oil starvation problems with the FE that I was aware of was the 427's at extreme rpm's. That's how the side oilers came about. Second, did you verify that your gauge is correct? I would install a known mechanical gauge and verify what your seeing with the factory gauge. Lastly, the pressure relief valve in the oil pump can hang up and blow the filter off on any motor, I've had it happen to me twice. Once on a buick v-6 and another time on a dodge 360. So it's not all that uncommon. Heck, we used to add shims to force the pressure higher! Hope this helps some.

I'm going to put a mechanical gauge on today, just to verify. Also I'm going to make sure that the sending unit wire isn't shorted somewhere as well, beats dropping the pan. Got everything back together and to this point at the end of the day, so was looking for some insight before I started guessing. On the 6 qts., there is a lot of discussion on 5 vs. 6, oil passage modifications etc. When I first got the car, changed the oil 4 + 1, and the stick read 1 qt. low. Searched a bunch of forums and came up with the 5 + 1 answer. Most of the folks that rebuild theses motors do some of the oil pressure mods, (which ones always a debate), some add HV pumps, (again a debate), and always crank scrappers and windage trays. The extra qt. is an easy fix for the front sump configuration, not so good for horsepower.

A piece of insulation was burned off the sending unit wire, along it to short sporadically. Insulated it, and now good to go. Thanks for the suggestions.

That is good news. Thanks for filling us in on the resolution!