Alignment of fittings.

[bugsy63]

Hi Guys

I'm seeking advice on the correct method of aligning a dash 8 45 degree bend for the oil cooler discharge hose on my IO-320.

Due to the installation of a 90 degree oil filter adapter, the alignment of this fitting is quite critical to ensure that the minimum bend radius of the oil return line is not exceeded. Lycoming list a maximum torque of 110 inch pounds for 3/8-18 NPT fittings, however, a further 180 degree rotation is required to achieve the required alignment.

Although I haven't scoured the lycoming manual to seek specific giudance, is anyone aware of a proceedure that allows alignment of a fitting in this situation after the torque limit has been reached?

Thanks in anticipation

[flion]

I wouldn't go past Lycoming's max torque, if possible. However, NPT fittings are designed to be 'clocked' within a fairly large range of tightness over 1.5 to 2 turns. This is the best discussion I've found on NPT fittings.

[az_gila]

Each insertion seems to remove a little bit (microscopic) of the plating/surface finish.

So if you unscrew the fitting, clean it well and add more thread sealant (Fuel Lube/EZ Turn/your favorite) and insert it a second time it will now screw in just a little bit further than the previous time for the same torque.

Repeat until the clocking is to your satisfaction.

As Patrick's link says, do not back off to reach alignment.

[aerhed]

Or, you might want to honk it into a steel plumbing part first. Inspect, then try it in the aluminum engine.

[bugsy63]

Hi Guys,

thanks for the replys. I'm certain, with the recommendations and advice, I'll get the issue licked now.

Just one thing I note, however, is that an -8 AN fitting (elbow, bend and nipple) most certainly has a 3/8-18 NPT on it. Using the torque limits for 1/2-14 NPT would mean an exceedance of around 50%. It would be a really nasty place to damage the accessory housing

Thanks again

[SMO]

Just an FYI, you can get an -8 AN fitting with 1/4, 3/8, 1/2, and 3/4 NPT on the other end, elbows or straight.

[skylor]

Originally Posted by bugsy63

Hi Guys,

thanks for the replys. I'm certain, with the recommendations and advice, I'll get the issue licked now.

Just one thing I note, however, is that an -8 AN fitting (elbow, bend and nipple) most certainly has a 3/8-18 NPT on it. Using the torque limits for 1/2-14 NPT would mean an exceedance of around 50%. It would be a really nasty place to damage the accessory housing

Thanks again

Oops, yep my bad. The standard AN 822 and 823 elbows are 3/8 NPT in the -8 size. Sorry about that!

Skylor