Register now to get rid of these ads!

Hot Rods Does this tank need a vent?

Discussion in 'The Hokey Ass Message Board' started by Deere boy, Mar 18, 2019.

  1. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    I'm using this tank from Speedway on a speedster. Cap says "open slowly". Do I need to vent it or the line somehow before filling it full of gas and letting it set in the sun?
    [​IMG]
     
  2. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,236

    oldiron 440
    Member

    All fuel tanks need a vent or at some point you will not be able to pull fuel out of it.
     
    5window likes this.
  3. 5window
    Joined: Jan 29, 2005
    Posts: 8,241

    5window
    Member

    Other than adding that the vent should have roll-over protection, that's all you need to know.
     
    loudbang likes this.
  4. Hollywood-East
    Joined: Mar 13, 2008
    Posts: 1,463

    Hollywood-East
    Member

    If the cap Say's vented..... It's vented, if not You need one
     
    31Dodger and loudbang like this.

  5. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    Okay, so educate me a bit please. I've been around a lot of old cars and tractors but this is the first time I've built something from scratch. Does it need to be vented from the neck, or can I put a T in the line below, but before a shut off valve, and run a line up to above the gas level?
     
  6. oldiron 440
    Joined: Dec 12, 2018
    Posts: 2,236

    oldiron 440
    Member

    You need to come up with a plan to replace the fuel in the tank with air as you use the fuel.
     
    Bandit Billy likes this.
  7. BJR
    Joined: Mar 11, 2005
    Posts: 6,998

    BJR
    Member

    The vent needs to be at a high point of the tank that is not immersed in gas. A vented cap would be the easiest for this tank. If you T into the gas line going to the engine for the vent, it will push gas out of the vent line.
     
    flatford39 and Beanscoot like this.
  8. onetrickpony
    Joined: Sep 21, 2010
    Posts: 518

    onetrickpony
    Member
    from Texas

    It is vented through the cap. It's what is called a "pressure/vacuum" cap. It prevents vapors from escaping the tank ( pressure) while allowing air in (vacuum) as fuel is used. That is the way all modern caps work. Pre 70's caps were just vented and allowed fuel vapors to just leave the tank. That was changed due to air quality issues.
     
    flatford39 likes this.
  9. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    Here's the bottom of the cap.
    [​IMG]
     
  10. Hollywood-East
    Joined: Mar 13, 2008
    Posts: 1,463

    Hollywood-East
    Member

    Does it say non vented? I would assume if it came with that tank, an there's no other provision... It's vented
     
  11. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    It says, " Warning Remove slowly. Fuel spray may cause injury."
     
  12. try sucking and/or blowing on that little hole in the center of the cap
     
    flatford39 and TrailerTrashToo like this.
  13. 5window
    Joined: Jan 29, 2005
    Posts: 8,241

    5window
    Member

    Rarely a good idea to "assume" matters of health and safety.
     
  14. 5window
    Joined: Jan 29, 2005
    Posts: 8,241

    5window
    Member

    Of course, we have all missed the obvious answer "CALL SPEEDWAY AND ASK THEM!"
     
    clem and Latigo like this.
  15. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    I thought about that, but I have found that there customer service people sometimes know less about these things than I do.
     
  16. Ding,ding,ding we have a winner.

    Sometimes the obvious answer eludes us all. :rolleyes:HRP
     
    Latigo likes this.
  17. Deere boy
    Joined: Jul 25, 2018
    Posts: 60

    Deere boy

    Speedway says it is vented.
     
    Hollywood-East likes this.
  18. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 1,013

    TrailerTrashToo
    ALLIANCE MEMBER

    EDIT: See picture in Post #9

    I have used this style of fuel cap on several vehicles (both on-topic and OT) - it is designed to be used with vapor recovery systems. I found that the cap is one directional on the blow-suck test. The usual parts stores (NAPA, blister-pack-city, etc) did not stock original replacement caps.

    I used a small drill bit to drill about 3 holes through the center disk. Go gently, the disks wants to spin in place. The cap will now pass the blow-suck test.
     
  19. Question...with the holes you drilled, are you not vulnerable to a leak and possible fire in the event of a rollover accident? Not trying to be a smart ass here, just want you to be safe.
     
  20. Put a vented cap on it. Done deal.

    If you can't find one at the autoparts go the local Harley shop and buy a right side gas cap (early style) they are about 11 bucks.
     
    31Dodger likes this.
  21. So
    you'll need a vent when you fill it- (air out)
    You'll need a vent when you drive it (air in)
    You'll need a vent when it gets hot
    (Pressure and vapor out)

    Pretty much any way you look at it is that you'll need a vent.

    A vented cap certainly could work to cover it.
     
  22. onetrickpony
    Joined: Sep 21, 2010
    Posts: 518

    onetrickpony
    Member
    from Texas

    That style cap will allow air in but not out. That is why it has the pressure warning. It will keep fuel from leaking out when it expands from heat. That said, they can cause problems on early iron that uses less than 5psi of fuel pressure. The pressure build up can cause flooding if it gets high enough to push the needle off the seat. Using an old style vented cap can help prevent those problems. That is why fuel pumps in the 70's started having vapors return lines.
     
    F&J likes this.
  23. Inked Monkey
    Joined: Apr 19, 2011
    Posts: 1,831

    Inked Monkey
    Member

    This happened to me! I used a vented cap and could not get the thing to stop drowning the motor. Ended up taking out one of the springs in the cap. Probably not the safest in a rollover, but with an RPU I'd probably be dead anyways.
     
    porknbeaner and F&J like this.
  24. One time when I was broke (common thing still actually) I needed a vented cap and had one that was not vented. Well I didn't have any money but I did have a drill and a tiny bit (like about 3/32 or 1/16) so I just drilled a hole in the center of the cap. I used that cap for a long time. LOL
     
  25. So when did this fascination with roll-over valves begin?
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.