Last week we decided to run a test of the oil pump as it is right now. Since the plunger-type pump didn't have a return spring, I weighed the piston and estimated the spring rate we'd need. Then Roger and Craig measured the inside diameter, outside diameter and length that it should have, and at the moment a set of springs is on order from
McMaster-Carr.
Also, we've got some castor oil and some Aeroshell 15W50. There's some Aeroshell straight-weight oil on order, too.
We hope to take at least a first pass at that this coming week.
One of the key unanswered questions that we'll have, is how much oil flow is enough?
While we were talking about the lubrication requirements I brought out the oil breathers. There are two of these, one for the forward case and one for the aft case. If you look closely at the blue engine you can see the copper ends where they go. On this engine the breathers are somewhat different. The picture shows one assembled and one opened up.
Left to right, you'll see the upper cap, then the oil screen and the oil drain, then the breather body. When it's assembled, there's a bit of play axially, so that the screen assembly can be pushed upward. I think that the internal pressure in the case does that. It's necessary for the oil vapors to escape, with the path being up past the conical bottom of the screen, through the screen, and out the top. Any oil that wants to can dribble down the narrow drain, where it'll fall on the crank journals.
When the engine's off, gravity pulls the screen assembly down (down is to the right; left is up for these in this photo) and that keeps large dust and small squirrels out. And even at that, it won't prevent squirrels from putting their acorns in the vent and clogging it.
Unlike a more conventional oil screen, this one is simply a guard to prevent debris falling into the engine. It has no filtering capability - or rather, it's got a negative filtering capacity. Remember that the oil system is a dead-loss system? If there's any debris in the oil, it'll get retained. It's the cleaner oil vapor that escapes. The crankcase has two drains, and it's important to drain those sumps often, apparently, since whatever oil is down there gets gradually dirtier.
If we can get the oil pump to lift about 12 inches then we can make a drain tank, suck from that, and have an oil return that way. We can put a screen in there somewhere, if we can achieve that.