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Hot Rods My car only runs well at at least 20 degrees initial timing. What gives?

Discussion in 'The Hokey Ass Message Board' started by Jasper6120, Aug 17, 2019.

  1. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    Hey Hambers
    Just a quick question that hopefully someone has a simple answer to.
    I have a freshly rebuilt 283 (bored to 292) SBC with an RV cam, 416 heads and Edelbrock Performer intake.
    I can get this thing to run pretty damn well. It lays rubber free and easy, but only with the initial timing set at at 20 degrees advance. Anything below that and I lose a lot of power down low. 12 Deg advance and its proper sluggish. One noticeable problem I have is that the car is reeeeally hard to start when cold. It only turns over well when its warm. 20 + degrees advance would be the cause of the hard starting yes? I was using an old points dizzy and just upgraded to an MSD ready to run. (21 degree advance bushing and light silver springs give me an all in timing at just below 3000rpm). I'll need to change the bushing to about 15 degrees if I'm going to stay with 20 deg initial, for a total of 35, however:
    I know folks say set the total timing and don't worry about the initial. But with the hard starting and all I figure I better investigate whether something is amiss in my setup. I feel that it may be running kinda rich too (though the company rebuilt my quadrajet for me - Hume Performance, swear that it is setup perfectly for my 283 as per my request) I'm keen to hear your opinions. Thanks in advance..!!

    **UPDATE**

    So I found a thing. Unless I’m reading this wrong it basically states that until 1969 SBC used a damper that had TDC marked at 2 degrees before the timing tab centerline. After that they went to a damper that marks TDC at 10 degrees before centerline (for the most part. Some are different). And apparently all aftermarket dampers have the later TDC marker. This to my sleep deprived brain makes me think that my 20 degree initial advance is ACTUALLY 12 degrees - taking into consideration the 8 degree earlier markings on the aftermarket damper. Performance wise this is all making sense. I WILL confirm by finding true TDC on the engine when I get some free time.

    “The pre-1969 damper has the TDC line on the outer ring at the 2:30 o’clock position- or 2º before the keyway centerline- i.e. the line is to the LEFT of the keyway, looking at the front of the damper or engine. The keyway is seen in the ID of the damper nose. Includes a majority of the 2.30" small journal main engines and the 1967-69 2.45" large journal engines.
    The damper used from 1969 to about 1995 (some 1978-86 GM automobiles do not use the 2 o'clock position balancer and associated timing cover where there is some overlap usage e.g. G-series vans which retained the 2 o'clock balancer while the passenger car and C/K light duty trucks transitioned over to the 12 o'clock position which used a centrally located timing pointer spot welded) has the TDC line at the 2 o’clock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold by the aftermarket, unless they're adjustable. The 2 o'clock position was reintroduced during the 1987 model year trucks with the 8" balancer (only with the LO5-optioned 350/5.7L).”

    Found on https://www.crankshaftcoalition.com/wiki/Timing_tabs_and_damper_TDC_lines_SBC
     
    Last edited: Aug 17, 2019
  2. gigem
    Joined: Dec 31, 2005
    Posts: 55

    gigem
    Member

    No answers for you, but that made me laugh... thanks in advance!



    Sent from my SM-G935V using Tapatalk
     
  3. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    I haven’t tried messing with the idle mixture screws yet, but if they are too rich this would cause the need for more advance timing yes?


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  4. 97
    Joined: May 18, 2005
    Posts: 1,483

    97
    Member

    Have you checked that the mark lines up when the # 1 piston is at TDC? If not could be one of two issues, either the outer ring on the balancer has moved OR it has the wrong timing pointer on the engine!!!
     
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  5. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    That’s a good point. I’ve thought about that. It’s just that trying to turn that crank is going to ruin my life. Kiiiiinda hoping I’ll go through the easy bits and find something there that fixes the issue before pulling radiator fans and such. It’s snug in there


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  6. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    It is the original 283 timing cover/pointer. The balancer is pretty fraesh but you can’t really get that wrong without a Thor spec hammer


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  7. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    The timing chain is also fraesh, I eyeballed my eyes off making sure those two dots on the crank and camshaft centered up nicely


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  8. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 1,858

    OLDSMAN
    Member

    If all else connected to checking timing, I would check to make sure that the outer ring on the balancer hasn’t slipped. If it is still the original that’s a good possibility
     
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  9. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    The balancer is a new one, so hopefully it ain’t out of wack


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  10. 5brown1
    Joined: Apr 13, 2008
    Posts: 181

    5brown1
    Member

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  11. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,285

    sunbeam
    Member

    Pull a valve cover watch #1 or 6 depending on which cover is off watch the valves on 1 or 6 as you turn the engine over when the exhaust is closing and the intake starts to open stop when they are open the same amount look at the timing mark it should be within 5 degrees or less. If the car has a manual trans just put it in high gear and rock it forward to turn the engine. There are what I call 12 clock 2 o clock balancers and marks
     
    Last edited: Aug 17, 2019
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  12. Ralphies54
    Joined: Dec 18, 2009
    Posts: 698

    Ralphies54
    Member

    Could the distributer be off a tooth?
     
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  13. slowmotion
    Joined: Nov 21, 2011
    Posts: 3,050

    slowmotion
    Member

    Lotta possibilities. Start by finding TDC, move forward from there.
     
  14. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

  15. shivasdad
    Joined: May 27, 2007
    Posts: 519

    shivasdad
    ALLIANCE MEMBER
    from Texas

    I'm interested too. Had a customer car recently with a 283 but unknown camshaft that runs best with 23 initial. Vacuum advance works, mechanical comes in smoothly and all in about 3000 rpm. Double checked timing marks with piston stop. New Holley 600. He's enjoying it as is and I drove it about 100 miles before being done. Still have a timing curve on the whiteboard in the shop. Still a head scratcher for me.
     
  16. David Gersic
    Joined: Feb 15, 2015
    Posts: 1,933

    David Gersic
    Member
    from DeKalb, IL

    If it runs good, you might verify TDC with a piston stop, check cranking compression, and then just leave it alone and drive it.

    Describe your cold hard to start. What’s it doing?


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  17. Desoto291Hemi
    Joined: Apr 21, 2009
    Posts: 752

    Desoto291Hemi
    Member

    I might be wrong but didn’t GM change the timing tab location some time ago back in the late 70’s? I seem to recall they did and the tdc mark on the balancer is Slightly different.
    Since this is a 283 and I assume an original timing tab,,,if a later model balancer is used it might be out a few degrees.

    Tommy
     
  18. Desoto291Hemi
    Joined: Apr 21, 2009
    Posts: 752

    Desoto291Hemi
    Member

    Here is another old country boy trick we did back when we didn’t have timing lights.
    We just set the distributor by hand and felt how it ran.
    I would try setting it higher and see if the engine will hot start.
    When it gets too high it will be almost impossible to crank over.
    Then set your light on it and see where your total is,,,if it reads 45 or 50 degrees then you will know your balancer is wrong.

    That might scare some people,,,it is an old hillbilly way of getting by.
    But then again,,,,a lot of those old hillbilly’s used to run shine in old rebuilt cars that could out run the law,,,and they won a lot of NASCAR races later,,,heh heh!!!

    Tommy
     
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  19. David Gersic
    Joined: Feb 15, 2015
    Posts: 1,933

    David Gersic
    Member
    from DeKalb, IL

  20. Blues4U
    Joined: Oct 1, 2015
    Posts: 3,818

    Blues4U
    Member
    from So Cal

    As slowmotion posted, confirm TDC first. After that, set it where it runs best and don't worry about it.
     
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  21. sedantudor
    Joined: Jan 28, 2012
    Posts: 57

    sedantudor

    I had a similar issue. In my case my vacuum advance was pulling to early. The vacuum advance on my sedan is adjustable and it was pulling in at too low of a vacuum. A simple adjustment took care of that problem. Does your car diesel at all during shut-off when warm or at operating temperature?
     
  22. buffaloracer
    Joined: Aug 22, 2004
    Posts: 774

    buffaloracer
    Member
    from kansas

    i'm thinking the same thing that slowmotion and sedantudor are. how does it work when you plug the vacuum advance?
    pete
     
  23. David Gersic
    Joined: Feb 15, 2015
    Posts: 1,933

    David Gersic
    Member
    from DeKalb, IL

    So, find TDC with a piston stop, then see where your tab is in relation to the balancer.


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  24. King ford
    Joined: Mar 18, 2013
    Posts: 1,225

    King ford
    ALLIANCE MEMBER
    from 08302

    Weelllll, this might be a bit " hillbilly " but when I worked for our county road department we had a LOT of 366 bigblock Chevys that were notorious for spinning the outer ring of the harmonic balancer. It was often necessary to retard the timing to reduce CO for inspection and I would then advance the timing until they " pinged " on a pull and back it off until the ping went away. A BUNCH of them went a BUNCH of miles this way!
     
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  25. Or time with a vacuum gauge. Time for max vac.

    Ben
     
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  26. Jasper6120
    Joined: Jul 18, 2007
    Posts: 462

    Jasper6120
    Member
    from Australia

    You might want to look at the update on my first post in this thread. The big advance is probably due to the fact that the location of TDC on the timing tab and balancer was moved in 1969. So aftermarket balancer with pre 69 timing tab will be off by 8 degrees ie the tab showing 23 degree advance will actually be 15 degrees.
     

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