Flow Ezy Fuel Filter... NPT fitting question

[Charles Davis]

I ordered a Flow Ezy fuel filter from AC Spruce with 3/8" NPT thread size.

When it arrives, the holes measure about .565 and a 3/8" AN fitting is way too small.  I assume AC spruce sent me a 1/2 fitting, so I call.  They say, no, you need an adapter.

Wanting to avoid an adapter, I get an RMA and order direct from the factory, a 4ILA-03-25-F3-B to be exact; should be a 3/8" fitting.

It arrives: same thing!

What gives?  Do I need to order a 1/4" fitting to get a 3/8 NPT?  

Thanks for any insight!

[D]

Hi Charles -

Looks like your new filter wants 3/8" NPT per the part number.  That's a different animal than AN.  If you want to transition to AN- fittings, you'll need an adapter.  It'll be either a 3/8" NPT to AN-8 or AN-6... depending on what sort/size of fuel line you're running.

Check out Summit Racing (www.summitracing.com) for the fittings.  Search for "AN to NPT" and look at the Product Lines from Aeroquip, Aeromotive, CSR, Earl's, etc.  Prices are usually better than the aircraft shops for the same products.

The "secret decoder ring" for NPT vs. AN fittings (that I found when I got hit by the same train about a year or so ago) is as follows:

For NPT (Nat'l Pipe Thread) fittings, the size represents the inner diameter (ID) of the hole through the fitting.  NPT is also a tapered thread that "seals" as you tighten it... although a thread sealer (e.g. - Bakerseal) is strongly recommended.

AN (Army/Navy) fittings are spec'd according to the outer diameter (OD) of the fitting.  The number after the dash (e.g. - AN -6) represents the number of 1/16"'s in the OD of the fitting.  AN fittings are flared and don't require a sealer.

Hope this helps!

D

[Charles Davis]

Yes, that helps a lot!

Very confusing when it first hits you!

Thanks for the reply.