Where to plumb oil separator return?

I am trying to set up an ASA air-oil separator on a very tightly cowled GP-4, with an angle-valve IO-360, front induction, rear governor set-up. There is insufficient side clearance to make a return port in a rocker box cover.

There is an unused plug on the stand-off adapter that goes between the accessory case and the prop governor. Does anyone know if that is a low pressure port I could use for the separator return line? It looks like it might be an 1/2" NPT plug. Anyone know for sure?

It won't be easy to plumb to there, if it is a low pressure port, but I think the only other alternative would be to modify one of the rocker box oil return lines with some sort of T fitting. Unless someone has another idea?

Thanks,

N729LS said:

There is an unused plug on the stand-off adapter that goes between the accessory case and the prop governor. Does anyone know if that is a low pressure port I could use for the separator return line?

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Turbocharger oil return port, perfect for your application. Note it's in the accessory case casting, not an adapter. There is an outlet port in the governor adapter, which connects to the oil line running to the nose case.

Oil Return

On Lycomimgs using a oil return line works too. One way is to install a T fitting (AN824-6) in the right rear cylinder oil return line. Cut & flare with the standard tubing tools. Install with center leg of the T pointing aft toward the firewall.

Don Broussard

RV 9 Rebuild in Progress

Dan: Thanks. That could, in fact, be what I was looking at. I will check today. The back side of this engine is so congested that it's really hard to see anything, no less get a hex wrench in there.

Don:

Do you think that a female/male AN6 union with a 1/8 NPT female pressure port would work? The 45? fitting in the head for the oil return hardline is AN6 male out. I could put an 1/8 NPT male-AN4 adapter in it to connect to the separator, which is AN4 male out..

I can't seem to find a T with AN6 female/male on the run and AN4 male on the tee. Anyone?

Hopefully, I'll be able to use the turbo return port that Dan showed.

N729LS said:

Dan: Thanks. That could, in fact, be what I was looking at. I will check today. The back side of this engine is so congested that it's really hard to see anything, no less get a hex wrench in there.

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Previous reports suggest that removing the plug has been a common problem. You may need a good hex drive socket and enough extensions to reach a breaker bar. A heat gun to warm the aluminum may help too.

Noticed that you're not a regular poster here. You know about the requirement to regularly check and clean the exhaust tap?

DanH said:

Turbocharger oil return port, perfect for your application. Note it's in the accessory case casting, not an adapter. There is an outlet port in the governor adapter, which connects to the oil line running to the nose case.

Click to expand...

I just installed an ASA separator and used this location. I have an O-320 and this was a 3/8" NPT opening in my case. My plug came out easily and I thought it was easier to work in this area than putting a tee in the returns from the rocker boxes. It is also low enough to allow a gravity return.

DanH said:

Turbocharger oil return port, perfect for your application. Note it's in the accessory case casting, not an adapter. There is an outlet port in the governor adapter, which connects to the oil line running to the nose case.

Click to expand...

That is what I used. It is working just fine after 600 hours.

I was unable to get the plug out of that port on my engine, even with heating it. After I snapped one good hex wrench and bent another, I gave up and went with plan B - tapping into the right rear cylinder oil return line as seen below. I used a -6 Tee and then a reducer coming off the T, I was not able to find a Tee that had the -4 center leg.