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npt, AN ?!

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  • npt, AN ?!

    this is probably going to seem stupid..
    fuel inlet rochester carb. I only learned to get "3/8ths brake line"
    I want to put a fuel regulator right up close to the carb..with one fitting.
    I can only guess that the carb takes a 1/8th npt (.405 inch? ), but I buy 3/8ths brake line to fit.. and the regulator looks to be the same. The measurement on outside of the thread is 12mm. this is where I am confused. on npt they got outside pipe diameter at 10.29mm. is it the same?

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    I found a male to male 6AN.
    this is similar to what I seek..but it is not a correct looking seat.
    what do I look for as a male to male with an end that looks like this:
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    is it "1/8th npt"? I never see the connection written as such..but seems by photo it may fit. (read edit below)
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    thanks for help.

    ok a measurement resembling something..

    the fitting that they called a 3/8ths brake line is 5/16ths, outside diameter of the piping, not the fitting, is a shy of 8mm...that makes it a 1/16th npt by definition. (the second photo from above- that fits the carb inlet)

    are the 1/8th npt and 1/16th npt threaded parts the same size or no?
    if not..1/16th npt male to male is non existent and I would be out of luck.

    someone must have hooked up to the rochester with some accurate numbers...anybody?
    I always just buy brake line... never payed attention to actual numbering.
    Last edited by boxer3main; April 12th, 2012, 07:13 PM.
    1 gmc + 3 subarus = 824000 miles

  • #2

    Re: npt, AN ?!

    I think I can help, but would you be able to post a pic of the inlet on the carburetor, Barry? The 3/8" brake line you show must seal to a 3/8" inverted flare fitting. What you have shown on the 3/8" brake line is NOT NPT thread and is not to be used in an NPT application.

    It's really no different than trying to glue them back on after she has her way.


    • #3

      Re: npt, AN ?!

      I think this is the doohickey you need:

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      But I need to see the inlet in the carb to be sure.

      It's really no different than trying to glue them back on after she has her way.


      • #4

        Re: npt, AN ?!

        You need a -6 AN to Inverted Flare.....You said 5/16, here you go......

        Last edited by TC; April 12th, 2012, 07:30 PM.


        • #5

          Re: npt, AN ?!

          hey thanks..
          I found the caliper is off by a mm.

          the standard inlet for the carb is
          I need male to male 1/2-20

          npt or AN does not do that number, and fitting is nonexistent from the web.

          I guess I can get within 1.5 inches of carb after flaring my own brake line. the regulator takes the same fitting as far as I could decipher.

          I did find 1/2-20 to all kinds of npt or AN.. but not fitting my quest.
          1 gmc + 3 subarus = 824000 miles


          • #6

            Re: npt, AN ?!

            Look here...



            • #7

              Re: npt, AN ?!

              I guess I can get within 1.5 inches of carb after flaring my own brake line. the regulator takes the same fitting as far as I could decipher.
              that sounds like a good plan. But make sure you know what the regulator takes. Usually pumps and regulators are NPT, so you'd need a fitting to mate it to the inverted flare tube. If it has an inverted flare seat in it, then it's probably inverted flare. If it doesn't, it isn't.
              My fabulous web page

              "If it don't go, chrome it!" --Stroker McGurk


              • #8

                Re: npt, AN ?!

                thanks for help.

                I had to think a little more..

                the little sube is complicated.

                the pump only woks if engine is running. a number of places to switch this, I donlt need to know..

                it also used a return line, crazy stuff happens when I don't.

                ie: I can't fill the tank more than halfway when I stopped returning to tank.
                I think it may have been using the expansion of the round trip to help the pump stay stable...and steep hills...and a cough at idle to off idle...

                Holley uses it simply calling it "high performance"

                I'll stop messing with made in china and get the holley 12-803BP (bypass). This is more money, but less expensive than a popping tank.

                being it is a weird subaru..even has a surge tank in the rear quarter, I will use this with a 5-8 psi pump, not the 14psi holley recommends to use with that regulator. They specialized american anyway.. I don't feel I am doing a wrong by going smaller.

                in this way (if you read this far)

                I can go get the 1/2-20 to 3/8 NPT as one connector, right next to fidgeting with fittings and flares.
                the bypass version for holley has an idle bleed, shuts off as soon as outlet is demanded (exactly what the subaru hitachi had built in)... I am quite certain that is the cough I have now, the regulator will fix it.

                thanks for help.
                I actually got confused over the caliper reading wrong...and wanting to go cheap on regulator.
                the BP version is a bit more..but knowing what it does, I will not get a pump yet. Wait for regulator that really knows how to return line.
                Last edited by boxer3main; April 12th, 2012, 08:49 PM.
                1 gmc + 3 subarus = 824000 miles


                • #9

                  Re: npt, AN ?!

                  I can do it with two fittings.......

                  These fittings screw into Rochester Carbs and convert it to -6 AN....

         (this one is for '75 and up Rochesters)

                  Then all you need is one of these fittings, it's a -6 AN female to 3/8 NPT male which would screw into your regulator......

                  Last edited by TC; April 13th, 2012, 12:44 AM.


                  • #10

                    Re: npt, AN ?!

                    yes, that is what I found. thaks for help people.
                    I may have the one inch..will double check.

                    Going to grab the whole pile at summit in one cart.

                    and swiveled.. I can level the regulator.

                    I was almost giggling at bigger than the SPFI subaru made for these (it was a little genius, I loved it).
                    making it even bigger, ensured cathode (protected), a chance to go even bigger with heat at the regulator (any pump I want) and just 1/16th in the throttle bore gained is somehow a steady 30cfm larger. The heat rise was a natural one after going cathode on the carb (live wires resisted).Now exactly injected with no troubled 1 time code ECU. Just needed much bigger fuel to create the same friction, preheat.

                    none of this really planned, the way the math played out. injection meets 34 year old electrojet...until seeing 43mm bore of monojet next to approx 40mm bore of the SPFI (singular point fuel injection).

                    I also learned the regulator for carbs to have a bypass was only recently put into production in 2005 by holley. I clearly remember this frustration in high school days. making thier own regulator proper enough.
                    the little sube has been there for more than 30 years..starting at 30 below with 1 to 3 psi fuel...and funny enough, that is where the epiphany came from local "hey why don't carbs have a bypass"
                    between the spec clutch (2002), the holley stuff, the brass copper radiator found in new old stock for a real fit..

                    I hope I am building a bigger little awesome once impossible. The boxer is not a pile of crap here local.

                    never thought to spend 100 for fuel regulation..but that is the last magic trick.
                    Last edited by boxer3main; April 13th, 2012, 07:11 AM.
                    1 gmc + 3 subarus = 824000 miles


                    • #11

                      Re: npt, AN ?!

                      npt to unf

                      ok griping done about fittings.
                      I looked up lowes hardware..
                      assuming it is npt stuff? just look in plumbers sections..should find what I need..
                      lowes stuff even mentioned gasoline etc.

                      seems I can hard line it with brass, flare my steel. elbows etc. All cheap.
                      the unique connection at the carb kinda gets on my nerves..I do not want to spend any more for a special connect. The rest can be cheap.
                      I will get it up close..and it does cost strangely.

                      I need to hard line to help hold up the regulator at the inlet side.
                      the bp model of regulator has inlet where normally holley regulators have an extra outlet. Thisis just right for my setup. in one end, out the other..return is on the bottom.
                      Last edited by boxer3main; April 13th, 2012, 12:02 PM. Reason: done bitching
                      1 gmc + 3 subarus = 824000 miles


                      • #12

                        Re: npt, AN ?!

                        inverted flare

                        found this at thirdgen forum. I am not the only one who got perturbed.

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                        this apparently does 3/8ntp, to inverted flare or whatever the never in english definiton is.
                        I can go back to my 2 dolar per 4 foot pre flared brake line again...

                        photo looks promising.

                        I need to hard line as simple as possible. 3/8th npt to whatver it is I have for gas line that is unf with a half inch connector and 5/16th fuel line.. you know it is exactly convenient and correct.

                        this an/npt stuff...holy cow.

                        this deciphered would need a clean start sticky thread.

                        it is every carb with a regulator known to automatic transmissions..
                        oh wait.. that overlapped something else.
                        Last edited by boxer3main; April 13th, 2012, 07:17 PM.
                        1 gmc + 3 subarus = 824000 miles


                        • #13

                          Re: npt, AN ?!

                          thread standards

                          if this is good enough, maybe keep it in the library of deciphering immortal confusion.

                          AN standard
                          unf standard
                          NPT/NPS standard
                          brass inverted flare

                          in some of the links there is conversions.

                          what I want must be real so very confusing and sophisticated.

                          5/16 tube (1/2-20 thread or -5an) inverted flare (this means female) to 3/8npt male.

                          these mixups clearly identify no standard.

                          4 standards to lead to no standard at all.

                          above can decipher what most want..browse the links. It is as retarded as it appears.

                          remember..words are confusing for the extra terrestrials who stand their ground with their standard...

                          "union", is another word for "connector"
                          "flare" goes with "tube",
                          "inverted flare" goes with "female"

                          and male.. well you have to look at drawings. IE:
                          I found -5an has the same thread as 1/2-20 unf..but to see how they coonect ..that may get a grinder.

                          this makes web searches turn in into 24 hour festivals.
                          Last edited by boxer3main; April 14th, 2012, 11:11 AM.
                          1 gmc + 3 subarus = 824000 miles