Intermittent oil pressure drop

Yes, you could have a loose connection to your sending unit. That happened to me.

But the last time it happened it ended up being a hole in the pickup tube, which was caused by the pickup assembly breaking loose from it's mooring and bouncing against the camshaft.

I found it by pulling the sump plate and observing the pickup tube was loose to the touch.

If ???? there is a terminal problem . It will be  a rod or main bearing.  I tend to go witha bad sender or instrument with  lose ground.  But take Larry's advice and check the 2 relief valves  and the screen. That's a inexpecive safeguard. and i would replace the valves if they look the least odd or have major burrs on them . small nic's can be sanded and scotchbrited away

Do you have a deep sump? At any consistent rpms? Is this happening when going around corners or straight down the road? Accelerating or at steady speed? Is there any sort of repeatable pattern or is it totally random?

Al, this is a head scratcher! I wish the problem could be diagnosed with clues from a consistent, repeatable, pattern...but it's occurred while cornering, on straights, and varying rpm's...totally random. I've inspected the oil sender's connections and they appear good, but I have no idea what's going on, or what can sour, within that VDO's cylindrical body!

Barry's mentioning 'terminal' damage gives me goose bumps. So I hope the baddest scenario is Terry's experience with a loose pick up, and damage, if any, is minimal. Terry also experienced a loose sender connection...If the sender is malfunctioning does that mean that the warning light and zero pressure gauge reading is totally false and it's in no danger of becoming  catastrophic?

I've been on cloud 9 since LimeRock because it ran without a burp or a fart all the way up and back at the highest rpm's that road, and my nerves, allowed!!...Makes me ill to think that that was the last hurrah.   

Really need this info and what type of sender you have to make a good diagnosis.

I'm assuming a 10-180ohm dual sender. Check the wires for anywhere they could have damaged insulation and are grounding out. To get both sides to act the same, the damage to both wires would have to be in the same spot. If the wires were simply disconnecting, the gauge would go to full and the light would not be on. It could be damage to the mechanical part of the sender, but it would be unusual to get intermittent readings like that if it was. If it was a damaged electrical part of the sender, one or the other could be affected but both would be odd. But since the problem is intermittent, if you can't find the damage visually, you won't determine the problem with any diagnostic test, short of just replacing the whole sender and/or wiring and seeing if it goes away. Or temporarily installing a mechanical gauge+sender to view while driving.

A relief valve sticking open would cause lower than normal pressure, but it wouldn't be 0 unless your oil pressure was marginal to begin with, and it certainly wouldn't make the pressure suddenly drop to 0 under what I'm assuming are cruise conditions.

As the others mentioned, a cracked pickup tube (or plugged strainer) is likely if you don't find anything with the sender wires.

justinh, I can't visually find any problem with the sender's wires.

I don't want to take it on the road so I fired it up in the driveway to see if I could induce a 'worrisome' incident...nothing!

Ran it for about 15 minutes at varying rpm's from 900 idle to a sustained 2000 and tweaking it up to 3000. Got the CHT up to 250 where it held steady. The oil temp up to 140. (Under driving conditions it usually reads 185) The oil pressure gauge read just shy of 60psi when first started...which it normally is...then settled back between 40 and 45 fluctuating with the rpm's. At idle (stop lights) it's usually about 25psi, so 40psi at idle is above what I normally see. My A/F gauge is very irratic but it read lean...if it read at all! The warning light never went on...which makes me think that I have to be on the road moving and bouncing for an incident to happen, which seems to mean either a flawed pick up assembly, or a sender in need of retirement, or an undetected damaged wire.

Any suggestions or theories from experienced SOC people I'd sincerely appreciate. I think it's logical that I first follow Jowdy's advice and then move on to swaping out the sender. I've got a VDO#360 006D on order...plus oil relief valve caps, because I might have to drill and tap out the stubborn one that refuses to budge! I'm going to weld a hex nut to that slotted screw cap so the next owner of this VS to won't have to sweat and curse as I have!!!

Check the pick up tube....  With extended sumps, some will work loose and as oil level varies they leak air into the system, droping oil pressure...  I've seen one stock pickup tube come loose, but that is normally quite rare....

If you decide to remove the pressure relief valves, Sears sells a 3/8" drive, big screw driver blade (it looks like a socket with a blade on the end) that should fit your valve caps.  Push hard on the ratchet end while starting them - they tend to be pretty tight.  If not Sears, find a Snap-On or Mac tool guy.