Scaled harmonic balancer and timing

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    Author Topic: Scaled harmonic balancer and timing  (Read 3800 times)

    Offline shadango

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    Scaled harmonic balancer and timing
    « on: June 10, 2009 - 02:01:48 PM »
    While I am waiting for my carpet and exhaust to arrive (next week sometime  :banghead:) I have timeto pnder other things....LOL

    I had the car running yesterday (checking out how the new headers sounded......LOUD!!!! COOL!!!! LOL) and hooked up a timing light......just playin' really.

    I didnt unplug the vac advance.....I know you are supposed to when checking timing....

    I found that I have a mopar balancer up front with timing marks/scale on it....

    When I used the timing light, the o* mark on the car's tab lined up with about 38* on the balancer scale.

    WHen I gassed it, the scale went away....

    So, can someone clue me in on how to read this scaled balancer?

    The car idles rough and lumpy, but ....not sure if thats because I have no pipes/muffs, or because I have a cam (I dont know for sure) or if something else is awry.  It does idle on its own once warmed just a couple minutes, and it doesnt seem to be running rich......shut it down and restart and it fires up really fast.

    I did take a ride up the street and once you get off idle it seems to go...I never got over 30 though.....throttle is a little touch off idle

    Again, I was just playing....cant tune right now because I have no exhaust and its just too loud for the hood.....

    But can someone clue me in a bit on the balancer scale thing?
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    Offline UKcuda

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    Re: Scaled harmonic balancer and timing
    « Reply #1 on: June 10, 2009 - 05:06:28 PM »
    At idle the vac advance shouldn't in theory make any difference but in practice they do usually advance the timing a bit.

    38* advance at idle is too much.

    When you gassed it in Park or Neutral the vacuum and the centrifugal advance both stepped in and of course your timing disappeared off the scale.

    I can't remember what the recommended initial timing advance is but if you set it to about 15* with the vacuum disconnected you will probably find the timing doesn't go out of sight when you rev it.

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    Offline MEK-Dangerfield

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    Re: Scaled harmonic balancer and timing
    « Reply #2 on: June 10, 2009 - 05:28:23 PM »
    Quote from: UKcuda on June 10, 2009 - 05:06:28 PM


    I can't remember what the recommended initial timing advance is but if you set it to about 15* with the vacuum disconnected you will probably find the timing doesn't go out of sight when you rev it.

    With a bigger cam, 12-14* BTDC is a good guess. Just be sure you plug your vacuum advance line when you unplug it to mess with the timing. You don't want your carb to be sucking in unmetered air.
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    Offline shadango

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    Re: Scaled harmonic balancer and timing
    « Reply #3 on: June 10, 2009 - 05:48:40 PM »
    Ok, seemed kinda high to me too....but its been a looooong time since I had to adjust timing in anything!  LOL

    Any idea as to why the timing would be this high? 

    I was told the engine came out of a good running roadrunner in favor for a big block swap....

    ...was figuring everthing would still be set from that car......

    I mean the engine does run and idles......maybe my RPMs were up too high....like I said I was just messing around and looking.

    SO am I reading that scale right then?
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    Offline 422STROKER

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    Re: Scaled harmonic balancer and timing
    « Reply #4 on: June 10, 2009 - 06:44:10 PM »
    Where is the vacuum line connected to on the dist?  If you are on manifold vac you could be high from that.

    Tom
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    Offline 71chally416

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    Re: Scaled harmonic balancer and timing
    « Reply #5 on: June 10, 2009 - 07:14:07 PM »
    What matters is the MAX advance you have with the vac line to the dist unhooked and the RPM held up to get max advance. Usually 2,500 to 3,000 rpm. With a small block you want 36* and with a big block the same of a little more, like 38* with stock iron heads. The important thing is your TOTAL under WOT (wide open throttle) when vacume drops to zero. If it then pings under partial throttle you either need better gas or you need to modify your vac curve. That's best left to a pro with a distributor machine. You might just have to unhook the vac if you get the total set right and it pings at part-throttle until you get it recurved.

    Once you establish total advance you can then see what it is at idle. It is whatever it is, and there's no way to tell until you set the total first. A few degrees off at idle from what it "should" be or "what the book says" it should be won't matter at all,
    like say 12* instead of 10* at idle, but 2-3* off of the ideal total mechanical advance under WOT can cost you 20-30hp on a small block. :grinyes: That's why the total is the important setting and the idle figure isn't.

    And it should be STEADY and not jump around. If it does besides the obvious worn timing chain syndrome you could have slop in your distributor gear to distributor shaft coupling or even vertical movement of the gear.  They used to make a collar that clamped to the distributor shaft to keep the dist gear from jumping up and down (just a collar with a set-screw that held the dist gear down), but the only way to eliminate slop in the slot is to weld some metal onto the blade and grind it flat to take up the slop. :2thumbs:
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    Offline shadango

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    Re: Scaled harmonic balancer and timing
    « Reply #6 on: June 27, 2009 - 02:57:40 PM »
    Ok...finally got around to testing the timing "hot".

    At about 1100 rpms (what it is idling at now)....44 degrees, with the vacuum advance disconnected and the port plugged. Revving doesnt take it off the scale now, just higher....

    That is assuming I am reading it right.....I am using the "0" on the stock timing marks as the pointer and reading the timing scale on the harmonic balancer.....am I reading it right?  I am used to reading timing using one mark on the balancer and the cast-in marks on the stock tab.....)  :clueless:
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    Offline 71chally416

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    Re: Scaled harmonic balancer and timing
    « Reply #7 on: June 27, 2009 - 05:33:40 PM »
    That's about 30* too much.  :grinyes:
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    Offline Chryco Psycho

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    Re: Scaled harmonic balancer and timing
    « Reply #8 on: June 28, 2009 - 03:24:58 AM »
    if it runs "right" where it is then you may have other issues with a slipped outer ring on the damper or the scale in the wrong place on the timing cover
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    Offline shadango

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    Re: Scaled harmonic balancer and timing
    « Reply #9 on: June 28, 2009 - 06:36:07 AM »
    Well, it feels like it is running too rough and while it runs better up top, it feels a little under powered.........but since there is no exhaust on it, I figured I would wait till thats on and then see where I am at....I guess it wouldnt hurt to turn back the distributor and see if it improves or not....
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    Offline Aussie Challenger

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    Re: Scaled harmonic balancer and timing
    « Reply #10 on: June 28, 2009 - 07:26:57 PM »
    Quote from: Chryco Psycho on June 28, 2009 - 03:24:58 AM
    if it runs "right" where it is then you may have other issues with a slipped outer ring on the damper or the scale in the wrong place on the timing cover
      Always check to see if TDC is correct, everything else is guess work. Also mark the centre hub on the balancer so you can see at a later date if the outer ring has slipped.
      Always disconnect vac advance when setting timing with a light, check to make sure that you have ported vac & not manifold vac at the distributor, remember that the vac advance can be adjusted.   :2cents:
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    Dave

    Offline moper

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    Re: Scaled harmonic balancer and timing
    « Reply #11 on: June 29, 2009 - 12:05:42 PM »
    Set the timing at 15° at idle, but the idle should be lower. Anything over 900rpm is IMO too fast. Then ajdust the carb. Until the timing curve and carb are dialed in, it may run like poo. So in order of operations is always timing first, then carb. 
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    Offline shadango

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    Re: Scaled harmonic balancer and timing
    « Reply #12 on: June 29, 2009 - 12:12:09 PM »
    I checked the plugs when I changed them out yesterday for new ones and they are perfect tan!

    So I am hoping that once the exhaust is on (in the shop now) and I can get the timing set right, she will run well....

    Just setting the timing back to 18 or so made a difference I could feel in teh ride down to the shop.......
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    Offline shadango

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    Re: Scaled harmonic balancer and timing
    « Reply #13 on: July 01, 2009 - 05:38:54 AM »
    Well, the exhaust is on (though not done....tweaking still needed)........

    Set initial tim8ing at about 14* and while it doesnt vibrate as much, I now have much less low end throttle response and a bog....that could be carb...but I also still have the issue of idle wanting to be high....in park, if I set idle at about 1000 rpm, it will idle fine...when I shift into drive thecar drops to around 400-500 rpm and idles really low and wants to die......I did mess with the mixture screws (edelbrock 1407 750 cfm carb/edelbrock performer intake) and tried turning in and out but it didnt seem to make a measureable difference.....

    I did all this with the vacuum advance hose disconnected and port plugged, and when I plug the hose back in the idle smooths out a little and jumps way up...that cant be right, can it?

    The distributor advance is using the "timed vacuum port" on the carb (pasenger side), not the manifild vacuum side.....

    I am going to check TDC (anyone have tips on the best way to do that?) and the balancer scale today after work....I am also going to try checking for vacuum leaks with carb cleaner....

    I was told the engine ran great when it was pulled...carb, dist. and all...so I cantfigure out what could have changed to make it run like crap....

    Now, I have all new electronics.....and no idea what the guy ran before...maybe he was set up with a MSD system or something?

    But can anyone confirm that I am reading the timing tape right?  I am using the "zero" line on the water pump housing tab as the mark and the scale for the reading....maybe I am doing that wrong?
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    Offline 71chally416

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    Re: Scaled harmonic balancer and timing
    « Reply #14 on: July 01, 2009 - 06:16:59 AM »
    I haven't ever seen a Mopar balancer "slip", but I'm sure some have. Let's assume you're hasn't. Just unhook the vac line to the carb and hold the engine up at about 2,500rpm and set the timing for 36* aligning 36 with the zero mark on the timing tab.  Make sure that's as far as it goes by reving it a little higher while watching the mark. If it runs OK there, you're good to go. Whatever the timing is at idle is a function of your mechanical advance inside the distributor. If it doesn't run right then maybe you have a slipped balancer hub and you can worry about checking your TDC mark then. Comprendo?  :2thumbs:
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