I'm trying to finish up the fuel tank install, and the fittings at the most inboard end seem too tight. The pictures show it out of the threads, and then tightened with a wrench a little bit. To tighten much more would take a lot of force.

Should I keep tightening it down? Is this part of how it seals? Or is this far enough?


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Are you familiar with NPT  or gas threads? the hole and the fitting are tapered.

I looked into it, thanks! I can't find a lot of specifics of how tight it should be. 

From what I have found, about 1-2 full turns after it's hand tight?

There is no rule except "snug." If it leaks, it is not snug enough. If you over tighten you can wreck the threads or even possibly split something.

I could not get your picture to appear, but as Geoff said these are tapered pipe threads.  The key to these threads is the use of the proper sealant.  In all actuality the name sealant is not quite right, but it is the normal term.  The "sealant" actually primarily performs a lubricating function allowing the threads to tighten properly.  There are rarely torque values published for tapered pipe thread fittings, but snug will create a proper seal with the right thread sealant.  Loctite 567 is the recommended sealant for aviation fuels.

Thank you so much!


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