Return Fuel line... Why?

Discussion in 'The Mixing shop.' started by Quick Buick, May 14, 2023.

  1. Quick Buick

    Quick Buick Arlington Wa

  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    Return lines in that era was "hit or miss".

    The driving factor was vapor lock, so in some cases the "mindset" was an AC car would be in a hotter environment, and the extra load on an engine with the accompanied heat from evaporator coil, compressor load etc., could be enough to create a hotter under hood condition creating a vapor lock, contrasted by a non-AC car. Cars in the late 60s and early 70s, with the EPA mandates, fuel quality/blends, also contributed to higher under hood, as well as engine operating temps, and issues with vapor lock.

    You almost cannot have a negative impact with a return line.

    If you can run a return, it will not hurt.
     
    12lives, Dano, patwhac and 1 other person like this.
  3. Dano

    Dano Platinum Level Contributor

    In '70 on a 350 A-body, only A/C cars got a return line (A/C included HD cooling but HD cooling itself didn't get a return line). In '71, HD cooling got a return line regardless of whether the car got A/C or not.

    So to your point, it was hit or miss and I guess in '71 they figured if someone was ordering HD cooling on a non-A/C car, then good chanve it was going to be used in a hot environment & the return line could be useful for preventing vapor lock.
     
    TrunkMonkey, 12lives and Quick Buick like this.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The return line circulates hot fuel and vapor back to the tank. The idea was to keep cooler fuel in the pump, and it's purpose was to prevent or lessen vapor lock.

    Bob,
    A description of the vapor return is in your 1967 Buick Chassis Manual, page 64-5, section 64-4, paragraph b.

    https://www.teambuick.com/reference/library/67_chassis/files/64-a.php
     
    Last edited: May 14, 2023

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