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bugsy63

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

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
 
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.
 
bugsy63 said:
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
Click to expand...

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

Skylor
 
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