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This topic has probably been covered, but while fishing around for the best sealant to use on my new project's fuel fittings (it's an '86 Vette, therefore EFI and high pressure) I found a lot of information on the web and in forums that bugged me. It involved #3 Aviation sealant and its clones.

It's great stuff. I've always used it to seal head bolts. It never hardens completely (like RTV does), which lets you retorque your head bolts even years later without concern. However, I saw a lot of folks using it on gas lines on the web. I know Permatex says it is resistant to gas, and I suppose it is. However, years ago when removing a head to change the gasket, I wondered how to get the persistent stuff off my bolts to reuse them. I found that immersing them in plain old isopropyl alcohol for a few minutes cleaned off the bolts like they were sandblasted! Modern pump gasoline contains ethanol or methanol, reactively almost identical to isopropyl alcohol.

So, just an fyi because I was shocked at the lack of easy-to-find info on the web for how to remove the stuff (and hence where not to use it). Much as I love the stuff, I'm not about to use it on a 40psi fuel line in a plastic car.

I plan on using teflon sealant. Not the tape, the paste. I don't want to trust the threads, even tapered, on metal-metal connections, and I don't want to be stuck with hardened sealant (or shredded tape) the next time I try to pull things apart. Suggestions welcome.
 

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Permatex #2 or #3 can easily be removed with isopropyl alcohol (rubbing alcohol) but not many people know that. Removing Permatex #2 and #3 from someone's fingers and from under fingernails is the reason modern gear heads don't like to use Permatex #2 and #3 . Most people prefer stringy sillycone sealant that stops up oil pumps and water pumps.

Permatex #2, #3 and Permatex Aviation Form-A-Gasket #3D is just like roofing tar, except it never hardens. I use that stuff on everything except fuel line fittings. It works wonders on the accessory side of gasket surfaces.
 

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Ditto MouseFink. Aviation is the best stuff out there. We use it the same as he describes. A little (keyword) "Ultra Black" RTV in the "corners", and they don't leak!

Jim
 

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Flared fuel line fittings should not require sealant. Like brake lines the flare is the seal not the threaded nut.
 

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