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Hot Rods Surge while driving... What can cause that??

Discussion in 'The Hokey Ass Message Board' started by mack57, Jun 21, 2015.

  1. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

    Happy Father's Day to all the Dad's out there!!

    My '48 Chevy has a surge as you're driving, not under acceleration.
    It's a 305 stock with a th350.
    Have had some tranny issues and wondering if this is a new symptom in that issue....
    Anything else that could be causing?

    Thanks,
    Mack
     
  2. saltflats
    Joined: Aug 14, 2007
    Posts: 10,672

    saltflats
    Member
    from Missouri

    A lean condition can cause this but we need more info on your setup.
     
  3. pottsie454
    Joined: Feb 12, 2011
    Posts: 399

    pottsie454
    Member

    If the motor is basically stock its more than likely a lean surge. Check your idle mixture screws for dirt or dust, and make sure your float levels are in spec. Lastly, for good measure check your timing, if your to advanced it could cause the surge too.

    Good luck!!
     
  4. 2racer
    Joined: Sep 1, 2011
    Posts: 960

    2racer
    Member

    That could be someone pushing you from behind... go faster
     
    clem likes this.

  5. Buddy Palumbo
    Joined: Mar 30, 2008
    Posts: 3,870

    Buddy Palumbo
    Member

    I'd bet on a lean condition .
     
  6. What carb? Maybe a miss......however, I like 2racer's answer
     
  7. Roger O'Dell
    Joined: Jan 21, 2008
    Posts: 1,143

    Roger O'Dell
    Member

    To much advance on timing
     
  8. pitman
    Joined: May 14, 2006
    Posts: 5,040

    pitman

    This problem usually stymies. Thanks guys for some insight on it!
     
  9. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

    Lol!! At this point a push would be welcome!!
    Thanks All! Check timing & carb. I'll let you know what happens.

    Thank You!!
     
  10. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

    Ok, timing is good, floats are good, jets are clean.
    Air/fuel adjuster is non-operational on left side facing the carb. The right side adjusts as it should. I took it all the way out and cleaned it. Then blew out the carb... No change.
    What to do next?
     
  11. pitman
    Joined: May 14, 2006
    Posts: 5,040

    pitman

    Inquiring (clueless) minds are listening! What might reveal in the way of change, if you backed off the timing a couple of degrees? (Any change)? If the car idles well, it doesn't sound as though you've got a vacuum leak-contributing to leaning out.
     
  12. Sounds like a fuel pump about to go away, to me....
     
  13. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

    Ok, took another shot at blowing out the air/fuel idle screw. That's working & found a vacc leak!! She is running like new!!!
    Thank You all for helping me through!! Time to cruise!!
     
  14. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

  15. What kind of manifold vacuum are you pulling at idle and at a steady cruising speeds? Is it steady or does the vacuum reading drift up and down a bit?

    The idle mixture screws should have no real effect on anything much above idle speed.

    If the engine is otherwise in a decent state of tune it could be a weak fuel pump, plugged filter, or a tank venting issue. But I've also seen instances where a float set 1/16" below specs was enough to create a noticeable surge at cruising speeds. At first I had a problem convincing myself that such a minor change could make the improvement that it did.
     
  16. 69fury
    Joined: Feb 24, 2009
    Posts: 1,419

    69fury
    Member

    i had a car surging at cruise- new plug wires and all 8 stayed lit-problem solved- taught me to make sure ALL is right under the hood and reminds me of the saying 98% of all carb problems are ignition.-rick
     
  17. mack57
    Joined: Apr 17, 2013
    Posts: 176

    mack57
    Member

    I did change the filter this morning also, as the bowls had a sediment in them. So changed the filter & cleaned them out. That may have had as much to do with it as anything else huh?
     

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