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Technical Carburetor heat soak / hot start issues

Discussion in 'The Hokey Ass Message Board' started by Devin, Sep 18, 2016.

  1. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Hello fellas. I realize that this subject has been discussed to death however my hot start issues have me confused. First of all, this is totally unrelated to the starter, the engine turns over just fine when hot.

    The engine is a 327

    tripower,- Rochester carbs on an Offy manifold exhaust heat risers are not blocked off. Carbs are separated from manifold with 3/8" phenolic spacers.

    Mechanical fuel pump with regulator set to 3 psi

    9.8:1 iron heads mildly ported

    Solid lifter cam, nothing too big. Just adjusted valves

    pertronix distributor with vacuum advance (manifold vacuum source). Timing is 14 static and 36 all in by 3000 rpm. Engine seems happy with this timing. Verified with vacuum gauge.

    The engine is in a hood-less roadster.

    This engine starts on the first turn and runs really great. Water temp stays at 180 no problem even when hot out. Once stopped, I cannot restart, the engine turns over and over. I can still see fuel squirting from accelerator pump when actuating the throttle after shutting off. The carbs feel very hot though even though I have a spacers between carbs and manifold. Wondering if I should block off the heat risers to the manifold?

    I can't figure this one out. Starts fine after cooling. Makes me not want to take the car out for a spin and park somewhere. Any suggestions? Thanks


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  2. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    More info needed.

    Ok, so the squirters made no difference. That in common sense means two possibilities. one is that when shutting down, the carb bowls instantly start boiling gas, causing flooding.


    two is a complete loss of spark


    I'd get it hot enough to do it again, shut it off, then quickly remove air cleaners to watch in each carb.
     
  3. steinauge
    Joined: Feb 28, 2014
    Posts: 1,507

    steinauge
    Member
    from 1960

    Do block the heat risers.Another thing that helped me was using wood or phenolic spacers under the carbs.Good luck.
     
  4. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    Thanks guys. The carbs squirt has after shutting off when I actuate the throttle linkage, they don't appear to be seeping. Verified by removing the air cleaner. What could cause loss of spark? Once cool, the engine fires instantly. I do have phenolic spacers but may need thicker ones. Will try blocking off heat risers. I didn't originally as I was worried about fuel vaporization and distribution issues, but I think this will help.


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  5. carbking
    Joined: Dec 20, 2008
    Posts: 3,196

    carbking
    Member

  6. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,925

    brokenspoke
    Member

    I learned a long time ago....most carb issues are electrical issues
     
  7. You have gas, so think electric. What does the spark look like at the plugs, if any? You are probably fine with the 3/8" spacers. What Pertronix do you have? It could have a module that breaks down when hot. At what point will it start again?
     
  8. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

    It's a pertronix I. I'll crank it over and see what the spark looks like. Anything in particular I should look out for? Weird thing is it runs great when hot, just can't restart immediately.


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  9. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    Devin
    Member
    from Napa, CA

  10. I've had HEI modules fail when hot and they did different things. The last one, I could run the car all day as long as it sat for no more than 10 minutes. Give it 15... no spark until it cooled off, maybe a 2 hour wait. The other would shut the car off on me when I was driving. Then re-start and I'd be able to move it 300' at a time if I was lucky. Again, let it sit a couple of hours and it behaved. But if you have spark & no start, this goes out the window.
     

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