Lycoming O-320 restrictor fitting - Alternatives?

[S. Soule]

The restrictor fitting for my O-320 D2G is a 45 degree AN823-4 with an insert/plug that has been drilled to 0.04". It goes in a hole in the engine case right next to the engine mount. It has to be clocked just right BEFORE you mount your engine because you are going to connect a hose to it. I used Aeroquip 303 hose. I should have used a "lifetime" hose because the 303 hose has to be replaced periodically and is very hard to reach, being behind the engine mount. The time came this month to change that hose and I fiddled too much with the hose fitting and jiggled the restrictor fitting and now have a tiny oil leak from the fitting, where it is screwed into the engine case. It seems to me that every Lycoming O-320 owner has the same issue with the hard to reach fitting. Wouldn't it be great to have a low-profile fitting for the engine case that, like a banjo fitting, could be clocked in any orientation and tightened? Or be able to take off oil pressure from some other location?

[Avanza]

The Cessna 172's since the restart of production use the front port of the right gallery for oil pressure pickup. The pressure reading at that point will be 8-10 # less than at aft end. This is in front of cylinder nr 1.

Good luck

[jrs14855]

The new Cessna location is so that Cessna can run 10 # higher pressure and still read the previous number on the gage. Highly recommended for better valve train lubrication.
A 90 degree automotive "street elbow" with a straight pipe to flare fitting orientated straight aft will usually help with access problems in the normal location. At least some recent manufacture engines have an additional port in the accessory case oriented straight aft.

[lr172]

I used a different fitting that can be installed with the engine on the mount. It is a brass fitting that is block shaped with a 1/8 NPT male on one side and a 1/8" NPT female in a 90* orientation to the male. It is quite small and has no 90* appendage that prevents it from spinning. You can install that fitting with the engine mounted, then install a straight AN fitting into it, with the restrictor on it.

Fittings available at mcmaster.

Larry

[jrs14855]

Originally Posted by lr172

I used a different fitting that can be installed with the engine on the mount. It is a brass fitting that is block shaped with a 1/8 NPT male on one side and a 1/8" NPT female in a 90* orientation to the male. It is quite small and has no 90* appendage that prevents it from spinning. You can install that fitting with the engine mounted, then install a straight AN fitting into it, with the restrictor on it.

Fittings available at mcmaster.

Larry

That is "street elbow" in the automotive world. NAPA has them. Used on certified Pitts. Large diameter rivet drilled #50 or smaller for restrictor, rivet pressed into male end.

[S. Soule]

The street elbow looks like a good choice. What are the odds that I have enough space to unthread my existing restrictor fitting and thread in the elbow? Anybody out there ever removed that fitting without loosening the engine mount(s) and moving the engine away from the engine mount?