Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: low end stutter

  1. #1
    Join Date
    Aug 2009
    Posts
    8

    Default low end stutter

    i have a 76 scout with rebuilt 345 and rebuilt 727, new plug wires, distributer and carb. vacum test shows to be ok. i can not get this low end stutter to go away did same thing with old carb, the carb is a350 cfm holley, pn 7448. any other ideas tired of throwing money in the wrong direction

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

    Default

    What's your timing setting? What happens when you block off the vacuum advance?
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  3. #3
    Join Date
    Aug 2009
    Posts
    8

    Default

    the timing is about 5 degrees and nothing happens when i un plug the vacum advance at an idle. its a new distributer with out gold box ive checked for vacum leaks pulled intake put new gaskets.

  4. #4
    Join Date
    Feb 2009
    Location
    Paso Robles, Ca
    Posts
    63

    Default

    When you say you have a low end stutter, are you talking about off idle during take off?
    Have you check your accelerator pump? If your not getting enough fuel on initial movement of the throttle, then this would explain it.
    Hope this helps.
    Rob

  5. #5
    Join Date
    Aug 2009
    Posts
    8

    Default

    can i adjust the accelerator pump carb is new did same thing with other carb its a holley 350 cfm pn 7448 what other possibilities is there

  6. #6
    Join Date
    May 2009
    Location
    AZ
    Posts
    21

    Default

    You probably need to adjust Acc. pump. does it squirt fuel into the carb whan you hit the throttle?
    Last edited by AZ scout guy; 08-27-2009 at 06:28 PM.

  7. #7
    Join Date
    Feb 2009
    Location
    Torrance, CA
    Posts
    154

    Default low end stutter

    Was the Scout originally set up for the electronic ignition but has been changed to a 'points' style distributor?
    Bill

  8. #8
    Join Date
    Feb 2009
    Location
    Paso Robles, Ca
    Posts
    63

    Default

    Quote Originally Posted by aaron View Post
    can i adjust the accelerator pump carb is new did same thing with other carb its a holley 350 cfm pn 7448 what other possibilities is there
    Note what AZ Scout Guy said. Check to see if it is squirting fuel when you move the throttle. I went through 4-5 "remanufactured" from Holley directly that had similar issues such as this. Some were lean, some leaked and another did not squirt at all.
    I ended up rebuilding my own and it works much better.
    Could you give us a little more info?
    Specifically what Bill was asking for... What has changed? Have you checked all of the connections? Does this happen when it is hot, cold or both?

    Thanks,
    Rob

  9. #9
    Join Date
    Aug 2009
    Posts
    8

    Default

    the studderis almost like clutch chatter, its an atomatic with 345 both rebuilt. i had the trans done, bought it with the motor done ,have receits. ive changed plugs, wires, cap, rotor, the ditributer was converted to electronic using msd box. the old carb i rebiult problem still accurde pulled intake replaced gaskets, same, bought the carb new fuel pump same thing.if i set the timing around 10 btc problem is less but pings to much but still excist other wise truck seems to run ok all day
    Last edited by aaron; 08-29-2009 at 05:33 AM.

  10. #10
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    If you're getting ping at 10 degrees, but not at 5, your problem may be in the distributor. The first thing I would do is drive it without the vacuum advance. Pull the line and block the carb side so that it can't suck vacuum. It might be that your vac advance is "fluttering" the timing as you give it gas. This could be caused by a power valve problem or by a vacuum advance problem, such as a crack or pin hole in the diaphram. A crack, at partial vacuum, does the open-close-open-close thing as vacuum increases, then stays open. Same as a pin hole, partial failure. Then it smooths out and gives you full timing.

    Ported vacuum is a smog thing, not a performance thing. Try it at 5 degrees with blocked vacuum. You may like the way it runs.

    It sounds like you have plenty of compression, but are you running rich? Could you have carboned up the valves/combustion chambers so that compression has increased already?

    If there is a chance of this, you might also want to try some sea foam. Use the ported vacuum line to the carb to suck it right out of the can. a few seconds at a time. When it starts to die, pinch the tube and rev it up. Tjem repeat.

    It sill smoke like crazy when you do this, so only do it when the neighbors are having a barbecue if you don't like them. Then pretend to be apologetic or just move, because they will be really mad.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •