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The oil sump plate from Sonex, is drilled for a return line from an oil separator. I don't understand why you would want to return oil to this location, that being the lowest point in the engine. It seems to me the oil return line would collect all types of debris and would need flushed out at oil changes. Plus, you have an extra length of hose filled with oil sitting at the bottom of your engine, not really circulating but at what, an ounce an hour? (I have no idea how much oil goes out the breather). Wouldn't it be better to return that oil to a higher location, if possible?

So, let's say you are filling the engine with oil for the first time. The oil will go down from the filler hole, into the sump and into the oil separator return line, filling it up to the level equal in height to the level in the engine. Now, as the engine runs, the oil separator does it's job of scavenging oil from the breather tube and sending it down its merry way to the bottom of the sump, via the oil return line, along with any contaminants found along the way, only to settle in the oil return line which is the lowest point in the system. Since this pathway isn't an active part of the oil pump system, I think it's safe to assume there will be very little movement of oil between the oil separator and the sump, thus a great place for crud to settle out. This could be a good thing of course, since it's not in the engine, but cleaning out the return line sounds like a lot of extra work every oil change.
I'm probably over thinking what must be a minor point as I couldn't find any history on it. And maybe I should have just ask a simple question from the get-go....Does the oil return line get filled up with crud? And is there enough room to return the oil at a higher location?

Late at night thoughts and getting ready to buy engine,
Darick

If you want the same oil sump plate without the extra hole, you can get it from Mofoco:
http://www.mofoco.com/item/EMPI_16_8964 ... IA/339/c78

I have no idea how the design works as far as the issues you describe... but I think folks who use an oil seperator are usually doing so for aerobatic (inverted) flight. In which case the oil system is effectively reversed (and effective) during sustained inverted flight, using this design. I think.

Without an oil separator I was getting a lot of oil on the bottom of the plane.

I chose to install the oil return into one of the valve covers, but I don't think there is any problem with using the sump plate. If you were clever you could use the oil return line as the method to drain engine oil at oil changes...kill two stones with one bird.

radfordc wrote:If you were clever you could use the oil return line as the method to drain engine oil at oil changes...kill two stones with one bird.

That's what I do!!! :)

Sounds like a good idea. After all, a bird in the hand is worth two in the sump.
Darick

If you are planning on using the machined sump plate I would sugest test fitting it to your case before you assemble your engine. The studs on the bottom of my case did not stick out far enough for the nuts to grab when using the thicker machined plate insteaed of the thinner stamped plate. You can put longer studs in the case if needed but once it is assembled you can't get to the one stud that holds the oil pickup tube down.

Keith
#554

Thanks Keith, I will make note of that.

kmacht wrote:If you are planning on using the machined sump plate I would sugest test fitting it to your case before you assemble your engine. The studs on the bottom of my case did not stick out far enough for the nuts to grab when using the thicker machined plate insteaed of the thinner stamped plate. You can put longer studs in the case if needed but once it is assembled you can't get to the one stud that holds the oil pickup tube down.

Keith
#554

I bought my engine much later than Keith, in Oct of 2012. My machined sump plate fit fine.

Mike
#439