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Thread: 345 Idles on four cylinders yet

  1. #1
    Join Date
    Jan 2013
    Posts
    4

    Default 345 Idles on four cylinders yet

    Put a carburetor kit in this 345 that has a history of idling on 4 cylinders. It runs better now, but still not firing an all 8 cylinders just above idle speed. Actually it probably does't do this "untill" you give it a slight throttle advance - Then you can here it labor on only 4 cylinders for a little bit, and after that, if you give it more throttle it will clear up and pull like a champ. The motor is in a 1966 1800 Loadstar farm truck. This thing has had a history of this for all it's life. ( 35 years) This most recent carb. tear down showed very little contamination any where. With the exception of a lot of black from the backfiring it goes threw when you advance the throttle. It is running a 2300 Holley with a governor set-up from the factory. Allen E., You told me to check the cylinders and find out which ones where not firing during this. It's the center two( 3 & 5 which I pulled ) and the # 2 and 8. Could this be any vacuum leak that is isolated to only that side of the intake? That would effect the idle though wouldn't it ? The low end Idle screws seem to be effective, and it runs smooth at absolute idle. At tear down I checked the throttle openings at idle and they seem to be synchronized with each other. I'm very puzzled at this time. Could anybody come up with some advice as to where I go from this point ? ? Thanks in advance to all the I H Minds I read at this site!

  2. #2
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    2-8-3-5 is the left (driver's side) carb jet not producing any fuel. There is a spot where your carb flakes out, then kicks back in. Yes, it could be a leak on that side, but my guess is that your carb is unbalanced and needs a complete rebuild or replacement, or there is just a piece of crud in it.... etc...
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  3. #3
    Join Date
    Feb 2012
    Location
    Near Seattle
    Posts
    21

    Default

    If it's crud, I have had great luck using either Seafoam or Amsoil PI to clear it up. Another possibility is the power brake diaphragm or the PCV is bad and causing a major vacuum leak.

  4. #4
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    Quote Originally Posted by carnuck View Post
    If it's crud, I have had great luck using either Seafoam or Amsoil PI to clear it up. Another possibility is the power brake diaphragm or the PCV is bad and causing a major vacuum leak.
    Having a bit of trouble with this one. The brake booster would show up bad all the time as a major vacuum leak, not just at partial throttle. The PCV, same story. I would also think maybe the vacuum advance is pulling a worn out set of points out of alignment, but if the 2-8 and 3-5 cylinders are the ones going dead all the time, we're looking at all of them fed by the same side of the intake manifold. That screams "carb." Every other cylinder from a worn out distributor just seems very unlikely as well. On the other hand, the seafoam wouldn't hurt.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  5. #5
    Join Date
    Apr 2009
    Posts
    7

    Default

    Looks like a older post, but if you haven't fixed your problem yet, it wouldn't hurt to check that the accelerator pump is giving both venturis of the carburetor even squirts of fuel.
    Last edited by khf; 01-06-2014 at 12:37 AM.

  6. #6
    Join Date
    Aug 2019
    Location
    Syria
    Posts
    13

    Default 345 Idles on four cylinders yet

    Still a devastating side even with the replacements. Hell Kangaroos are so well stocked they arent replacements, they are equals.

    I got my tickets for this match With Greg.

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