Fired the engine up, 50 psi oil pressure, no problems, all great..then on a test drive the pressure dropped to 10 psi, I limped it the block and a half at idle. I checked it with another gauge, sure enough 5-10 psi at idle. Beats the crap out of me, I've built a crapload of engines, this is the first one that had an oil pressure hiccup.
I'm using an aftermarket HEI distributor and am wondering if that might be part of the problem (the oil pump drive end). The oil pump is a Mellings hi-volume. I spun it with a drill before running it in order to prime the engine and it had 30 psi on the drill motor.

 

Was this a new build? All brand new bearings? Sounds like the cam bearings are worn out...

 

Does the pressure go up as you rev the motor up or does it sit at 5-10 above idle?

 

No, basically, I'm an idiot, apparently in the block cleaning process I missed something there was crap in the oil pump, which killed it dead. I took the pump apart during the build to make sure nothing was left in it from Mellings and to oil it. When I pulled the pan today there was some kind of funk that went through it, nasty, scored the heck out of it. Anyway, I pulled the #1 main and it seemed OK, the oil filter apparently stopped it. I couldn't get the pan all the way off, so I had to pour kerosene into it, slosh it around and open the drain, did this about 500 times, 3 cans of carb cleaner later, unbolted the windage tray so I could at least feel all the way around the pan. Put it all back together (by Braille) with a new pump and it has plenty of PSI. For those scoring at home it was a low budget rebuild but I pressure cleaned the block, someplace somewhere I just missed some crud. Hopefully that's the end of it.

 

OK fired the shitbox up, good oil pressure, drove it about 2 blocks to my neighbors, let it idle (180 degrees) on the way back to my house I jumped on the gas a little, no problem, as I let off I noticed the oil pressure fluctuate then head right for the basement. POS had about 20 psi and started dropping even more on the way back I idled it into the garage and shut it off. It's been my experience that with oil pressure losses, 2 strikes and you're out so tomorrow I start pulling the engine to see WTF is going on. I've NEVER had an oil pressure problem with any engine that I've built and this SOB is driving me nuts. So it's coming all the way apart.