AN6 fittings with mechanical fuel pump

[Steinerj56]

I recently installed my rebuilt engine and am looking at finishing touches. I bought a Jeg's fuel pump and a straight 1/4 NPT to AN6 fitting. I installed only to find out when I installed it the end that went into the fuel pump stripped out. The aluminum came apart and was leaking when just sitting with out engine running. Threads were gone. I thought about trying to run a tap but since it was fuel related I decided it was best to just replace. I ordered one from Summit to see if it was any different. Look almost identical. Bought a Russel brand fitting also.

I started to finger tighten and found it only went in about 3 threads before it got tight. almost the same as the original. I am using a brass barb hose fitting on the inlet so I installed this and found it went a little further. I cleaned threads as best as possible and the AN fitting only went a little further. The whole threaded portion is approx. 1/2 inch deep and I am only going in about 1/4 inch before it gets tight. Before I throw away another $45 and buy a better brand fuel pump do you have any thoughts or ideas how to make it work better? should I use a non hardening sealer like permatex #2? Or just get it tight and see if it leaks?

[benny70]

I had the same sort of problem. Anyone find a solution?

[VetteVet]

I think the fuel pump is tapped for straight threads like brake lines not NPT. That would explain why the NPT -AN tightens up quickly.

[Steinerj56]

summit says fuel pump inlet and outlet is 1/4 NPT. Is that not the same size as a 1/4 NPT straight to 6AN fitting?

[SS Tim]

If it were me, I'd confirm it is not a "close enough" metric thread on either part. Then use a NPT tap to deepen the tapered threads so I could run the fitting in about 75% of its threaded length. Might need to grind the tap off or find a bottoming tap depending on the hole depth. Make sure you use a light, flushable grease on the tap to catch what it can and reverse blow the hole often. By that I mean use a tube extension on your blow gun and push it fully in before triggering the air and keep blowing as you extract it.