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Pipe gurus.......difference between NPT and Flare?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BurbinOR, Jun 5, 2001.

  1. BurbinOR

    BurbinOR 3/4 ton status

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    Am relocating my electric pump on my Blazer.......have the Bosch pump and the standard IROC steel canister filter, as well as 3/8" flared fuel lines. No problem with the bending, etc. Question is the hookup from flared fittings to what appears to be NPT (female national pipe thread) on the filter. The 3/8" NPT flare fitting on the fuel line screws in what seems perfectly into the canister filter..........BUT there is nothing in the filter to "block off" the fuel line. Hope this is making sense.

    Is there a difference 'thread pitch wise' between NPT and flare fittings? Thought flare fittings were pipe thread..........

    Anyway, might I need an adapter from pipe to flare to enable the flare fitting to seat and seal off?

    Any input/opinion/help is much appreciated as always.

    <font color=blue>'79 ONE TON TPI K5 - See it at---&gt;<A target="_blank" HREF=http://www.blazzinor.coloradok5.com>http://www.blazzinor.coloradok5.com</A>
     
  2. 85m1009

    85m1009 1/2 ton status

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    You will need an adapter to change from flare to npt. The flare thread is not tapered and will not seal to anything except a flare fitting. Hope this helps.

    <font color=yellow>Steve Frisbie</font color=yellow>
     
  3. HarryH3

    HarryH3 1 ton status Author

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    On an NPT fitting, the threads themselves are the "seal". On a flared (also think "compression") fitting, the threads only apply pressure to the flare. The flare pressed against the inverted flare seat is where the sealing occurs. Thread sealant isn't required (and won't help seal) a flared fitting.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
    It's a great day to be alive...
     
  4. pcorssmit

    pcorssmit 1/2 ton status

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    Not sure about the TPI filters, but the factory truck TBI filters use a metric fitting that is a bitch to find adapters for.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  5. HarryH3

    HarryH3 1 ton status Author

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    I found the adapters for mine at a place that specialized in parts for foreign cars. They know all about metric stuff. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
    It's a great day to be alive...
     

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