Advance adjustment(s)

Discussion in 'Electrical and Ignition' started by canyncarvr, Aug 29, 2012.

  1. canyncarvr

    canyncarvr Well-Known Member

    Messages:
    82
    Likes Received:
    7
    Joined:
    Dec 31, 2011
    Location:
    State of Jefferson
    Local Time:
    11:44 AM
    Greetings:

    Re: A one-each 'performance' distributor, aluminum body. One of the <$200 units, not any fancy billet blingy.

    It was advertised as having 'quick' springs in it. I haven't been INto it to check, but mechanical is all in by 1800rpm or so.

    What I want to resolve is an idle speed issue. I'm running a 3844 HE cam. It will idle at 700rpm fine (oil at 60psi), but it won't DROP to that idle from a higher RPM without pulling the engine speed down with the clutch.

    The idle speed won't drop 'cuz the springs let the advance work, which raises the engine speed, which keeps the springs stretched..a positive feedback kind'a thing.

    I would prefer the idle to be around 1000rpm or so, but can't GET there because of the 'loop': Idle is either lower than I'd like (no advance) or higher than I'd like (mechanically advanced) if I don't pull the rpm down with the clutch.

    I see the lighter springs available for the distributor, but the only 'kit' I see that would get me stiffer springs is P5153446 and I don't need all the stuff that part comes with.

    Any input on some method other than stiffer springs to get to where I want to go rpm-wise?

    Maybe a set of springs that isn't $40?

    FWIW: Mechanical is set to 28º, total to 44º, ported vacuum. That's a good bit lower total than usual to resolve some detonation I get when not using rather 'exotic' fuels (Trick or VP...or clear 92 with a 5% toluene add). HE specs the cam at 175psi, my engine is 175.

    Any pointers appreciated! Thanks!
     
  2. 73SwingerBuild

    73SwingerBuild Well-Known Member

    Messages:
    1,006
    Likes Received:
    19
    Joined:
    Feb 22, 2010
    Location:
    Rhode Island
    Local Time:
    2:44 PM
    I had/have the same problem with the mystery 340 I bought and put in my swinger (I call it a mystery because I do not know what cam/compression it has and it basically came to me as a 2,000 mile crate motor.

    I believe the distributor is a stock Mopar part (based on the part number), but I have no idea what the springs are. I found that the issue goes away if I run the motor hard for a few minutes and then park it, as it idles fine right around 700-800. However, if I rev the motor in neutral it will let the idle creep up to 1,000-1,200.

    I wonder if I'm having the same issue with the springs that you have. Waiting for somebody more experienced to chime in here.

    Thanks for posting.

    -Mike
     
  3. canyncarvr

    canyncarvr Well-Known Member

    Messages:
    82
    Likes Received:
    7
    Joined:
    Dec 31, 2011
    Location:
    State of Jefferson
    Local Time:
    11:44 AM
    My distributor isn't new..but the car has been sitting in the garage doing nothing for a l-o-n-g time since it WAS new. I may find out differently when I get around to taking the distributor apart, but I am assuming the mechanism in mine to be in good shape.

    I can think of several things that might cause what you describe in your rig...a sticking spark advance mechanism being one of 'em.

    I see the YH (Mallory) 'kit' at Summit for a lot less than I had been seeing it. With a bit stiffer spring set and changing the stops, I think what I'm looking to fix will be fixed.

    I'm not looking to get into a 'It doesn't matter!' session, but my initial is 2º, and I want to change that, too.

    ...by doing the same thing: Tightening the springs and changing the stops.

    It'll all get sorted eventually!
     
  4. BillGrissom

    BillGrissom Well-Known Member

    Messages:
    7,197
    Likes Received:
    321
    Joined:
    May 10, 2009
    Location:
    Sacramento
    Local Time:
    11:44 AM
    Can't help you fix it, but can help confirm your theory of the positive feedback. The manual for the Holley Commander 950 (can find online) talks of setting the timing advance curve with a flat spot around the idle rpm so the engine doesn't want to run away when it sees more advance and likes it. I imagine the factory distributor weights were designed the same way with some deadband around idle.
     
  5. srixon4406

    srixon4406 TURBO TOAD

    Messages:
    1,306
    Likes Received:
    86
    Joined:
    Oct 1, 2010
    Location:
    Clarklake Mich
    Local Time:
    2:44 PM
  6. canyncarvr

    canyncarvr Well-Known Member

    Messages:
    82
    Likes Received:
    7
    Joined:
    Dec 31, 2011
    Location:
    State of Jefferson
    Local Time:
    11:44 AM
    Yes. My Holley has access to both....ported and manifold. The engine will not 'settle' to idle with either. Vacuum advance is not causing the problem.

    At idle speeds with the HE3844 there isn't much in the way of vacuum, period. It's not as bad as the 292 PurpleShaft I used to run. That gave me pressure at idle. Great for vacuum boosted brakes!!! (kidding)

    I'm sure there is NO 'flat spot' in the YH Mallory distributor with the flimsy springs.
     
  7. ryanwblandon

    ryanwblandon Well-Known Member

    Messages:
    98
    Likes Received:
    1
    Joined:
    Jan 26, 2010
    Location:
    Breinigsville, PA
    Local Time:
    2:44 PM
    Have you tried looking into the springs on the distributor? If in fact they put light springs in you can purchase springs to adjust how fast you want your advance to come in. I have to do this back in the day I went with too light of a spring and had the same issue. Usually two springs I had one light and one medium, it did the trick. You may have to play around to find your perfect fit.
     
    • Agree Agree x 1
    • canyncarvr

      canyncarvr Well-Known Member

      Messages:
      82
      Likes Received:
      7
      Joined:
      Dec 31, 2011
      Location:
      State of Jefferson
      Local Time:
      11:44 AM
      Some notes that may be helpful to other Mallory YH (Mopar Performance) distributor owners....

      I used Mallory's kit to tune my distributor, Mallory PN29014:

      Mallory29014distkit.jpg

      As noted by ryanwblandon, my MP unit was setup with two pink springs which gets you a single stage 'matched spring' advance. Mallory's notes in the kit say that any YH unit PN that ends in -05 will have two pink springs. The mechanical stops were full open which provided 32º total mechanical advance. I started with a 28º total @2200rpm/2ºATDC @750rpm initial.

      I installed Mallory's recommendation for springs: Purple/brown. The purple spring is loose on one end which gives the curve a 'two-stage' effect. I adjusted the mechanical stops using the 20º tab from the kit. MP setup info lists 32º for my heads ('69 X). I was after something in the vicinity of 12ºBTDC initial with the listed 32º mechanical total.

      The stop tabs on the YH advance mechanism are iffy. The plate is sloppy, making it easy to end up with the two stops at different settings. The differently marked tabs are less than stellar when it comes to setting the stops. Even with making sure the stop-tab plate is 'equal' on both sides, the 20º tab fit differently from one side to the other. A bit of 'tweak' to the tabs will take care of that. DO take some care when setting the mechanical stops if you want both of 'em the same.

      The end result was a 33º total @3100rpm, a 12º initial @900RPM. Just a tad 'off', but something expected considering how loose the stop mechanism is designed.

      The vacuum can on my MP distributor is stamped '11R'. With vacuum attached, I had 52º @3300rpm.

      I did notice the timing tape appeared to be considerably more steady AFTER the spring replacement.
      I have read opposite explanations of what CW and CCW accomplishes, but what mine does is pretty much opposite of what I typed. Full CCW on my 11R marked can locks the vacuum out. At least to the point of putting 20" to the can.

      There is no movement of the pickup when adjusted to full CCW up to 20".

      My can took 7-3/4 turns to get to full CW. At that setting; advance starts at <1", max at 8".

      Adjusted four turns CCW from minimum; advance starts at 8-1/2", max at 14".

      Adjusted six turns CCW from minimum; advance starts at 9", max at 12".

      The plate assy was a tight fit in the distributor body. It had to be pried out. That made reassembly a pain when fussing with the vacuum can tab. A bit of look-see will likely show where the plates are binding on the body. In my case, where the screw tab was bent on the plate had a couple rough spots. A touch of a file (keep any filings off the pickup!) to those spots made the fit a LOT easier.

      My idle is much better. It will still hang when the engine is hot..but not to the extent it did prior. A 12ºBTDC sure helped the brake booster! I used to 'run out' of power brakes on a regular basis. Yeah...I have a vacuum 'storage' can, but it happens to be sitting in a 'spare parts' box..NOT on the car. A whole lott'a good THAT does, 'eh? :-k

      The car runs considerably better. Part of that surely due to adjusting the 4-corner idle mixture screws. A completely non-scientific nor mathmatically correct fuel consumption 'test' (looking at the fuel gauge) showed a considerable increase in fuel efficiency. Engine runs hotter, starts a tad harder. By 'harder' I mean it used to fire with just a t-o-u-c-h of the starter, now it cranks a revolution or two. Not a big deal.

      IF you are running an MP distributor, don't hesitate to get it tuned. I should have done it LONG ago. Simply didn't get it done.

      A btw..but with a carb sync tool connected to the manifold/port nipples on my Holley the difference measured between the two isn't much..a couple of inches off-idle is all.
       
    • Kendog 170

      Kendog 170 Member

      Messages:
      24
      Likes Received:
      4
      Joined:
      Mar 10, 2016
      Location:
      Tewksbury Ma.
      Local Time:
      2:44 PM
      Sounds like you need to change one spring to a heavier one. I have a BB with the Mr Gasket springs and had to leave one stock spring in.
       
    • Mattax

      Mattax Just the facts, ma'am FABO Gold Member

      Messages:
      4,007
      Likes Received:
      1968
      Joined:
      Feb 7, 2013
      Location:
      Phila. Pa
      Local Time:
      2:44 PM
      Thanks for posting. That's pretty similar to the cans I've experimented with.
      One of which is graphed here: How To Limit and Adjust Chrysler Vacuum Advance Cans
      about 1/2 way down, a from Chrysler built MP small block distributor.
      :thumbsup:
       
      • Like Like x 1
      • canyncarvr

        canyncarvr Well-Known Member

        Messages:
        82
        Likes Received:
        7
        Joined:
        Dec 31, 2011
        Location:
        State of Jefferson
        Local Time:
        11:44 AM
        Yes. All that is in another thread. I have some 'test' springs on the way to try out. There are Mallory springs I have that might be close; purple/orange maybe.

        If my 'test' springs don't work out (Mr. Gasket 929), I got a Crane kit part number from Mattax that will do the trick. That 'kit' is $40, so I'll try some of the springs I have (or are 'in the mail'), first.

        I think the 'opposite' write-ups I've read on the subject get that way from being unclear about what 'more' is. Adjusting the can in a CCW gives you 'more' alright, but not 'more' timing. It gets you more diaphragm restriction, more pressure against the diaphragm, but LESS timing.
         
        Last edited by a moderator: Nov 26, 2018
      • Kendog 170

        Kendog 170 Member

        Messages:
        24
        Likes Received:
        4
        Joined:
        Mar 10, 2016
        Location:
        Tewksbury Ma.
        Local Time:
        2:44 PM
        Keep us posted when you figure it out. I'd like to know the results.
        Thanks and good luck !
         
      • Garrett Ellison

        Garrett Ellison Amateur driver on public roadway, do not imitate..

        Messages:
        89
        Likes Received:
        59
        Joined:
        Jan 1, 2018
        Location:
        Southwest VA
        View My Photos
        Local Time:
        2:44 PM
        Very good advice in thread, sometimes you can overcome the light springs by legnthening the advance slots and then welding back material toward shaft side. This puts the springs in a stretch and will usually extend rpm they advance to but will also prevent advance at idle. If it isn’t enough to keep the weights in at idle and you don’t want to fight different spring weights you can tie two or three coils of spring together with safety wire. Another option is to drill advance weights to lighten, but not completely through. Use a 5/16 bit. If you take too much out by accident, you can tap hole with a 3/8-16 bottoming tap and blue loctite in a socket head Allen to put half the weight back in.
         
      • canyncarvr

        canyncarvr Well-Known Member

        Messages:
        82
        Likes Received:
        7
        Joined:
        Dec 31, 2011
        Location:
        State of Jefferson
        Local Time:
        11:44 AM
        The drilling part I realize is an option; one I haven't gotten to, yet, don't know that I'll have to. Adding weight with a set screw..that is a great idea.
         
        • Thanks! Thanks! x 1
        • Garrett Ellison

          Garrett Ellison Amateur driver on public roadway, do not imitate..

          Messages:
          89
          Likes Received:
          59
          Joined:
          Jan 1, 2018
          Location:
          Southwest VA
          View My Photos
          Local Time:
          2:44 PM
          You can also use a 13/64 if you get close, that way you could tap 1/4 20 set screw in to add weight back. If you need to put all the weight back, use all-thread cut off flush and file/grind smooth. If one needed to add extra weight in, lead shot under a very short set screw epoxied in place. I wish badly for a distributor machine... we very much need an exhaustive online directory for spring and weight combinations to come up with different curves. It seems that almost every combination requires quite a bit of trial and error and custom tuning to get things optimized, it would help tremendously knowing what combination would provide what curve beforehand.
           
        • Garrett Ellison

          Garrett Ellison Amateur driver on public roadway, do not imitate..

          Messages:
          89
          Likes Received:
          59
          Joined:
          Jan 1, 2018
          Location:
          Southwest VA
          View My Photos
          Local Time:
          2:44 PM
          What we all really need is a locked rotor distributor and an affordable analog timing control with adjustable dip switch presets for rpm limit, advance/rpm curve, and vacuum advance with a map sensor or throttle position sensor. A lot easier than pulling the distributor apart to make changes.
           
        • RustyRatRod

          RustyRatRod Just another dumbass. FABO Gold Member

          Messages:
          46,898
          Likes Received:
          11566
          Joined:
          Jun 7, 2010
          Location:
          Georgia
          View My Photos
          Local Time:
          2:44 PM
          All in by 1800 is WAY too early. Typically, depending on many factors, all of which you left out, the "all in" RPM is around 2500-3500, depending on all the factors you left out. Give all details regarding your build. Engine specs, manual or auto, what stall speed converter if auto, gear ratio, vehicle weight. You know. All those important factors you left out?

          Until then, ALL advice you've been given is useless as tits on a boar hog.
           
        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

          Messages:
          4,007
          Likes Received:
          1968
          Joined:
          Feb 7, 2013
          Location:
          Phila. Pa
          Local Time:
          2:44 PM
          Guys, guys, guys. This thread was revived because Canyncarvr wanted to make correction to his own post from 2012 about vacuum advance.
          @toolmanmike fixed it (I think).
          His current development is
          This one about Mallory YH-YT Distributor springs
          :thumbsup:
           
          • Thanks! Thanks! x 1
          • canyncarvr

            canyncarvr Well-Known Member

            Messages:
            82
            Likes Received:
            7
            Joined:
            Dec 31, 2011
            Location:
            State of Jefferson
            Local Time:
            11:44 AM
            Thanks for saying.

            Does that mean the tits on my boar hog are no longer useless? Should I post here the timing specs for my HE3844 just in case some one wants not to bother with looking 'em up? Oh my...I think I left out the 1.5:1 rocker ratio I used with my HE aluminium (sic) adjustable rockers! Oh my #2: I left out that I had my custom JE pistons KoolKoated AND I used C/A gapless rings! These errors may prove fatal I'm afeared. :drama:

            ...just kidding folks... Then again, a local tuner prepped my Holley 750 before I even bolted it on. Who knows the foils and errant catsasstrophes which may be wrapped up in that.

            p.s.
            Some facts about the car and maybe answers to some questions can be found in my signature.
             
          • RustyRatRod

            RustyRatRod Just another dumbass. FABO Gold Member

            Messages:
            46,898
            Likes Received:
            11566
            Joined:
            Jun 7, 2010
            Location:
            Georgia
            View My Photos
            Local Time:
            2:44 PM
            You know man, I responded in kind to try and help. With answers like this, I'll be darned if it'll happen again for you.
             
          • canyncarvr

            canyncarvr Well-Known Member

            Messages:
            82
            Likes Received:
            7
            Joined:
            Dec 31, 2011
            Location:
            State of Jefferson
            Local Time:
            11:44 AM
            No offense(s) intended. Some light-hearted jousting? I s'pose. My apologies for any infringement.
             
            • Like Like x 2