Oil Pressure Drop to 0

have you tried hand lapping the relief plunger to the seat ? also, since you said this started when you installed the push rod tubes, the tubes themselves are just return lines, there is no oil pressure in them, the push rods do carry pressure have you checked that all the rods are seated correctly into the lifter bodies ?

The saga continues.  We determined that cylinder #3 had a good bit of blow-by prior to the piston traveling to the bottom and the the exhaust valve opening.  So, I ordered, and we installed a NEW ($$$$) Millenium cylinder hoping that would stop the oil pressure drop by not "cooking" the mineral oil (single viscosity).  Nope!  Next, we replaced the oil pressure regulator spring and plunger.  Better cold pressure but at about 30 minutes into flight the pressure begins to drop to 25 psi (still in the green) and then to 20 psi (top of yellow, bottom of green on MY gauge).  Let it cool and the oil thicken, and pressure is once again up to 30+ until it gets to a temp of 175 or so, then it slowly drops to 25 psi again.   Only thing left is a new set of oil pump gears and cover plate.  I can locate old new stock gears but no cover plate whatsoever.

Keep in mind, I did not have any oil pressure issues until we did the top end starting with new STC'd push rod tubes.  I called Continental Engines, and the Tech reps just scratch their heads.  Any suggestions?

Thanks for the advice.  We used a bench tester and the gauge is dead on correct. 

I'm surprised but try another gauge, etc

Just completed installing the Tennessee Real Gasket push rod tubes, new cylinder gaskets, bead blasted pistons, installed new rings, bead blasted valves and reseated them.  Filled with mineral oil and ground checked, no leaks.  1 lap flight, no leaks.  Compressions in the high 70's.  All's great right?  Nope.

I took her up for what was to be an hour of flying laps at 2500' and then checking for leaks.  On the third lap around around my oil pressure quickly dropped to zero and temp went over 220.  I immediately landed and taxied to the maintenance hangar.  No leaks, no oil traces.  Pulled the oil screen and it had a bit of carbon but no metal.  Pulled the oil pressure regulator and did find a fleck of carbon on the seating face of the plunger.  Great!  That's it.  Wrong.  Ran it up, good pressure.  took off and 3rd lap around same thing pressure drops to zero.

Checked screen...clean; check pressure plunger...nothing.  Drained the oil and flushed out the sump and fuel pressure seat.  refilled with oil.  Great pressure...until the 3rd lap then same thing.  My AP decided to drain the oil again and this time go to my normal Phillips 66 20/50 thinking the mineral oil is getting too thin and bypassing the plunger seat.  Good idea, but it didn't work.  Same result.

I called Contental's Tech support and talked to a really nice guy but he said it's a simple system, so wheat we did should have fixed the problem.  Only think he suggested was replacing the plunger, spring, and refacing the seat.  Ok, parts ordered...cant find the 88 degree cutting tool yet.

Can anyone give me any other suggestions?  This was not an issue before we installed new rings, pushrod tubes and gaskets.  HELP!!!