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Building an Aerovee turbo Onex with Dynon avionics and an EarthX battery. After adding oil to the engine I removed the lower spark plugs and rotated the engine with the starter to check oil pressure. EarthX spins the engine pretty rapidly. Plane is still in my shop (along with spouse’s plants) with thermostat set at 70 degrees 24/7. My EFIS was showing oil pressures of around 76 psi after two ten second spins with the starter. Onex VDO (80 psi) is not listed as a Dynon option in their data base so EFIS reading was suspect. Checked psi with an inexpensive O’Reilly gauge and was seeing about 87 psi (half way between 75 and 100). Ordered a Dynon recommended 150 psi VDO and installed. EFIS registered around 99 psi. Drained the oil (very very slow from the mini sump so left it drain over night). Removed both the Oil Relief and the Control springs. Control plunger (rear, short spring) came out immediately. Replaced it without modification. Oil relief plunger (forward) did not appear to have come out so I spent a day reviewing how others had removed a stuck plunger. Next day I found it in the oil drain pan. It apparently fell out overnight (perhaps even the first overnight). Given the high pressures, I polished the plunger with 3M wheels but did not use emery cloth. Oiled and replaced the plunger all the way up with it on a half inch diameter dowel and it fell out almost immediately several times. Inserted plunger and spring (with great difficulty) and turned the engine a couple of 10 second periods. High psi still, showing 96 psi on the EFIS. Bought the Harbor Freight oil pressure kit and it also showed 96 psi so am now confident in EFIS/new VDO readings. Drained the oil again, removed the oil relief plunger and this time spun the plunger (on a dowel in a drill) against emery cloth, then sand paper and polished on 3M wheels after. Oiled plunger, when pushed in fully by the spring, would fall out in one or two seconds. Replaced (again with great difficulty) and readings on the EFIS showed 88 psi. I’m assuming given the oil is room temp that my oil pressure readings are still too high. Given how much pressure is required to compress the Relief spring I’m beginning to wonder if the spring is flawed. Has anyone else had a similar problem or a faulty Relief spring?

Tom Jones
ONEX 0133
Aerovee Turbo 0838

I had the same problem with one Aeo Vee I built---The bypass hole that is drilled into the plunger hole
was ABOVE the bottom of the plunger hole ---The oil pressure had to lift the plunger
to bypass the oil which raised the pressure-- I reduced the diameter of the plunger about .020 diameter for about
1/8 inch from the bottom ---This allows the oil to escape without lifting the plunger more than needed --
The valve will still function as it supposed to-- Merle

I too had extremely high oil pressure. On my first engine start, the top mount oil cooler burst. Second start oil filter gasket blew out. I replaced the rear plunger spring with a much weaker one from local hardware store. Oil pressure still high but not excessively so.