understanding a low oil pressure 360

70 Duster Herb said
I don't post here much, but none of my research has produced much. Everyone always pointing to galley plugs or just random things to attempt to help.

360 rebuild
5w-20 lucas break in oil
solid lifter roller tipped adjustable rockers
new bearings fresh hot tank reassembled, 90-degree oil filter housing with WIX filter.

Running idle cold oil pressure at 10 psi
spun the oil pump with a drill pre-start up and post start up; I get 25 psi with no oil up top and when I position the cam and crank 2 separate positions both rocker shafts get 25psi. low speed on my drill, I increase speed pressure goes up.

it seems I have all plugs in and have verified all but two, not sure if 7.5 inches down the oil port on the China wall indicates no plug or if it's there, but through all I have read it's there. and behind the oil filter housing haven't looked yet, But I remember seeing one, but I'm old and have slept and drank since then.
spun pump with oil filter off (nice mess because it wasn't on purpose) and getting a lot of oil there.
Rockers are getting a lot of oil while I spin the pump manually, flows out of heads on to the headers So I'm getting oil throughout engine.

running out of possibilities.

Kind of thinking out loud here: If no plug under the 90-degree oil filter housing, should be no pressure at all.
if the pump where bad there would not be pressure or very little while spinning manually.
Best I can tell the oil, while engine running, is leaking off somehow and somewhere or not getting picked up.
I was mulling this over and I can't think of where the oil is going. only thing I can come up with is that the pump (suction side of the milling pump) is pulling air at a higher rpm than the drill is making, or the higher rpm is producing enough pressure to overcome the pressure side but before the pressure gauge, gasket. I did use the oil pump gasket and torqued to spec.

I have compared pump drive shafts and I get full engagement.
When I did start the engine, it sounded good nothing rattling or knocking or pinging.

Does anyone have a different theory? same? looking for ideas before I remove the oil pan and 90-degree oil filter housing oil pump engine and brainstem.
thanks y'all

Oil pressure is a balance situation. The oil pump does not produce pressure, it produces flow. If you install the oil pan without the crank and cam in place you will get oil coming out of the galleries, but no pressure. The pump has a pressure relief valve that controls the maximum pressure, not the minimum.
When you install all the components, those "leaks" you noticed with no parts installed, are mostly plugged with those parts. The clearances are controlled leaks to allow fresh cool oil into the wear surface.
You have to check every bearing or journal clearance when assembling a new engine. It is almost common these days for bearings to be packaged wrong. A 0.010" US rod bearing shell on a standard journal will be tight. That same shell pair on a 0.020"US journal, will have 0.010" too much clearance. This allows oil to excessively leak out, providing low oil pressure. A high mileage engine may have main and rod bearings that are copper all the way around. Oil pressure when first started and put in Drive may be enough to keep the idiot light off, but after getting well warmed up that light will be flashing at a stop sign or red light. It is most likely no the oil.pump, but the worn bearings.
Con rod oil flow can be controlled with the bearing clearance OR the rod side clearance. In a land speed trials engine, they push the RPM limits hard. So in those engines the rod bearing clearances may be high with fairly high pressure to keep the bearing shells and journals from touching much. That would lead toscuffing the bearing and probably turning the bearing. In this case they control oil flow through the bearing by the rod side clearance. Using a tighter side clearance holds the oil in the critical bearing shell and journal. Remember these engines run at high RPM and full throttle for the better part of 5 miles, not 1/4 mile. At Bonnyville the air temperature is typically 100°F+. It will be 80°F+ at 5:30 or 6:00 AM when things get rolling. Cars that set a record speed the day before get first shot at the cool air, to possibly repeat it.

RustyRatRod said
:rofl: