Inverted oil sump port education

sbalmos · #1 09-09-2016, 06:50 PM

Hi all,

I need a bit of education or at least a talking through. I have a IO-320-E1A originally off a Citabria. It's one of those sumps with a vertical oil suction tube inside, and was factory STC'd with an inverted oil system. At one point or another during the engine's life, it had a full Christen inverted oil system installed.

For various reasons, I cracked off the sump last week. I was surprised to find the suction tube had no oil screen on it at all. This seems to be because the central 1.5" port, which is normally plugged off, has a reducer screwed in it, so a large AN elbow fitting could be installed. Don't know if this would've been part of the normal setup for an inverted oil system. Anyway, apparently the suction tube fits straight down into this reducer, so the screen (which I have bought a replacement one) won't even fit on. And the only way the suction tube would get oil is if this elbow is connected to one of the other ports on the sump.

Like I said, I'm completely ignorant of how an inverted oil system would've normally been plumbed to the sump, so maybe this was normal to not have a screen inside to begin with? Can I remove the reducer, plug the central port back up with a plug (I have one of those also, I know it's a special size), and thus I'm guessing the screen will properly fit on the suction tube then, allowing the tube to suck straight from the bottom of the sump? I /really/ don't like the idea of my whole oil feed being dependent on a tube connecting from one port of the sump to another.

--Headscratching in The Queen City

BillL · #2 09-09-2016, 07:09 PM

Scott,

Christen has a manual on their system that will explain all the workings, flows and components. Just google for it. I downloaded it for understanding the half raven. Sorry, but I don't remember all the particulars, and you should compare pictures of your parts to help identify.

edit - here is a link for the by-page version. email me and I will send a pdf, but the link can he zoomed for detail.

http://musclebiplane.org/htmlfile/invert.php

sbalmos · #3 09-09-2016, 07:33 PM

Ooooookay... Now it makes sense. Took more Googling than I would normally expect. For others' reference, I found a copy at http://monrv-3.fr/docs/Christen.pdf. I think the previous engine owner did a bit of a hack job. I recognize parts now. Where the Christen system has its 810-S strainer pickup feed to the oil valve, my engine (still?) has a quick-drain valve. In the other ports I now recognize the Christen sump weld boss for the return fitting, and the 804-V sump fitting feeding the engine pickup tube from the oil valve.

So, looks like tomorrow I'll be wrenching off the sump fitting as I thought, or at least attempting to. Then I can reinstall the sump strainer screen I have, as "originally designed".