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SBC woes, runs great until....

Discussion in 'The Hokey Ass Message Board' started by Stevie Nash, Apr 23, 2013.

  1. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Former owner of my 59 F100 built the sbc. It runs great for the first 5 minutes then starts to sputter. Doesn't stall, but it does run rough.

    One thing I'm concerned about is he didn't put a vent in the gas tank. Is it possible it's creating a vacuum and starving for gas? That's the only thing I can think of. It also has a mechanical advance which I've never had before.

    Any other thoughts or confirmation of my suspicions?

    Stevie
     
  2. Larry T
    Joined: Nov 24, 2004
    Posts: 7,659

    Larry T
    Member

    It'd be real easy to check. Pull the gas cap off, drive it down the road and see what happens. If that makes you nervous, I guess you could just check and see if the gas cap is vented.
     
  3. Buford
    Joined: Aug 30, 2001
    Posts: 314

    Buford
    Member

    I'd start by checking fuel pressure. Good luck, Frank
     
  4. fridaynitedrags
    Joined: Apr 17, 2009
    Posts: 402

    fridaynitedrags
    Member

    Plug a vacuum gauge into the intake manifold and see what the motor's doin'.
     

  5. Lukcarnut
    Joined: Apr 6, 2013
    Posts: 41

    Lukcarnut
    Member
    from California

    Sounds like a fuel delivery problem to me, possible you are creating a vacuum in fuel tank i would do what Larry T said before any thing else. How is the fuel line run close to headers or exhaust, vapor lock? If fuel is all good check into ignition... coil is old and overheating?
     
  6. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    That's exactly what I was going to do tomorrow. Bought the truck in January and trailered it home. Just now getting all the changes done and driving it for the first time this spring. Still too damn cold! :eek:
     
  7. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Could be. Might be sticking on?

    Can just the electric choke be replaced?
     
    Last edited: Apr 23, 2013
  8. black 62
    Joined: Jul 12, 2012
    Posts: 1,895

    black 62
    Member
    from arkansas

    3 month old gas ?
     
  9. Grumbler
    Joined: Mar 2, 2009
    Posts: 358

    Grumbler
    Member

    Yes but just see if it's fully open when the engines warm.
     
  10. F-ONE
    Joined: Mar 27, 2008
    Posts: 2,273

    F-ONE
    Member
    from Alabama

    Most likely the F-100 is rejecting the transplant, anti rejection drugs may help but who'll write the script?

    Check for a dirty gas tank or clogged filter maybe water in the fuel. A dirty tank and lines will turn the best carb into shit real quick.
     
  11. I had a F-100 with a cleveland , started fine then turned to shit in a few minutes turned out to be a capacitor in the dissy.
     
  12. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Good stuff! But it's a 370hp runner with a mild cam. Try to build that cheap with a Y-Block.

    No apologies here...
     
  13. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Just put 15 gallons of premium in her...
     
  14. henry29
    Joined: Sep 5, 2007
    Posts: 2,835

    henry29
    Member

    Bad condenser will do that, Is it points or HEI?
     
  15. Fenders
    Joined: Sep 8, 2007
    Posts: 3,922

    Fenders
    Member

    Oh good.
    Maybe he could'a done that yesterday....
    Now I'll wait until his report tomorrow before adding any once-removed probabilities.
     
  16. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    hei
     
  17. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,352

    Mr48chev
    ALLIANCE MEMBER

    If it has a brand new shiny gas cap I'd bet on it having a cap that isn't vented even though it may have been bought as a vented cap. I went through three new Stant vented caps on my 51 Merc before I got one that was actually vented. The first time I walked a mile to a gas station for gas and back.

    Either loosen the cap and try it or run it until it stops and take the cap off and see if you hear a big gush of air running into the filler neck along with the sides of the tank popping back out.

    Then if that doesn't do it go after the electrical end of it.
     
  18. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Update... it's not the gas cap. It appears that the cap is vented. Drove it with the gas cap off and still the same thing. On to the next thing... carb and electric choke.
     
  19. landseaandair
    Joined: Feb 23, 2009
    Posts: 4,406

    landseaandair
    Member
    from phoenix

    Don't know if you said it was heat related or just time, but also check for cracks or pinholes in the pickup tube and fuel line before the pump that might be pulling air.
     
  20. Rocket man 88
    Joined: Sep 23, 2007
    Posts: 121

    Rocket man 88
    Member

    sounds like a carb problem...runs great when cold choke on rich, then stumbles on the warm side when choke should be open....either you have a sticky choke or you have a vacuum leak...could be a hose-gasket-or on the carb itself(throttle shaft?) is it mix'n the ratio right? adjusted properly.....timing isn't of is it?
     
  21. The HEI ignition modules and coils, can be heat sensitive.


     
  22. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Well, found a couple of problems. Timing was WAY off. Then tuned the Holley carb, runs like a champ!
     
  23. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Update... After the tuning and driving it a few times, the problems returned. Swapped the holley for an edelbrock that I had sitting on the bench, thing purrs like a kitten.

    Never had a holley before, don't think I will ever consider having one again.
     

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