Timing won't stay set

Discussion in 'Classic Mustang Specific Tech' started by TD68302, Nov 14, 2008.


  1. TD68302

    TD68302 New Member

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    I have 302 .040 over, dart II heads, comp cams hyd. flat Magnum cam 292 Ad. duration, 244 @ .050", .534 lift w/1.6 roller rockers, Mallory unilite distributor mechanical advance, 4.11 gears, C-4 Tranny.
    Question: Ignition Timing will not stay set, I can set it take it for 15 mile drive, Timing will advance 12 - 14 degrees. Why won't my timing stay set???:shrug:
    Any ideas??
     
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  2. hotcobra03

    hotcobra03 Active Member

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    Loose chain?
     
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  3. TD68302

    TD68302 New Member

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    Chain is new. Maybe 1000 miles on it.
     
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  4. bnickel

    bnickel Founding Member

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    it's either going to be the timing chain or the distributor itself, if you're sure the distributor is not physically moving then there are no other options it has to be one of the two.
     
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  5. hotcobra03

    hotcobra03 Active Member

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    Dumb question what about vac advance what set up u using
     
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  6. bnickel

    bnickel Founding Member

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    he's not, mechanical advance unilite dizzy
     
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  7. hotcobra03

    hotcobra03 Active Member

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    My bad.hey do you have another dizzy to rule it out.i have heard you can ck timing by turning engine by hand to watch rotor movement.you probably know all this all ready
     
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  8. woodsnake

    woodsnake Active Member

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    Did you lock tite the bolt that holds the cam gear in place, and tighten to the correct torque value?
     
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  9. zookeeper

    zookeeper Founding Member

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    I'd mark the distributer housing with a Sharpie and make sure it's not moving. It's not unheard of for aftermarket holdown clamps to be off, allowing the housing to turn.
     
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  10. ForceFed70

    ForceFed70 That's why they call it "dope" Founding Member

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    I'm confused as to why you guys are pointing to the timing chain. I can't see how that would effect his ignition timing without messing up the valve timing.

    I would also suspect a problem with the hold down clamp.
     
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  11. hotcobra03

    hotcobra03 Active Member

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    I understand your point.it appears everone here is mechanically inclined .i dont think he is telling whole story.sounds like it keeps adv n and he keeps moving it back.sharpie would be my next but he hasnt said he tryed to turn dizzy by hand no wrench yet to loosing.i think it would be very loose to change after 15min drive?
     
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  12. zookeeper

    zookeeper Founding Member

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    If the cutout on the clamp is too deep, the bolt could be tight, yet the clamping force on the distributer housing isn't enough to hold it. There is simply no other way I can see for the timing to keep advancing itself. Mark it and I'll bet we see that proven.
     
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  13. hotcobra03

    hotcobra03 Active Member

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    Never worked on a dizzy yet but his spark adv is mech .like weights and springs .anything their if not im going your way .thats for info .my youngest boy is turning 16 and i a almost mint 86 olds 442 with 28k on it.and i thinj it needs a valve job.i got it as is and the trans was smoked,taps when warm .was stolen before i got it .
     
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  14. TD68302

    TD68302 New Member

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    The hold down is good and strong, the dizzy itself is not moving
     
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  15. hotcobra03

    hotcobra03 Active Member

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    With your type of dizzy ,base timing is set at idle.as rpms increase timing advances from only that response?does idle effect base setting?
     
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  16. zookeeper

    zookeeper Founding Member

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    Let me see if I understand this correctly: you set the timing at (for examply) 12 degrees initial advance (at idle), verifiy it with a timing light, then drive the car. When you return from a 10-15 mile drive, you re-check your timing with a timing light and now it's for (roughly) 28 degrees intial advance? And you're positive the distibuter hasn't moved? Unless your internal advance mechanism underr the breaker plate is sticking,I honestly don't think that's possible. My car would not even run if it had that much advance at idle. Have you checked the advance curve with a light? I feel this is much more important. Set the timing at idle, then while still holding the light on it, increase rpm's to (about) 3,000 and verify two things: first check to see that your total timing is about 32-34 degrees total, and second that the timing advacne process is smooth and it returns back to the initial 12 (or whatever) degrees you set it at. It's possible that both springs have come off I suppose, that's the only other thing that affects timing advance besides the distibuter housing.
     
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  17. TD68302

    TD68302 New Member

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    Yes as RPM increase, so does the timing.
     
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  18. TD68302

    TD68302 New Member

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    I have checked the advance with the timing light and it goes up and down as it should. Everything under the breaker plate is loose and lubed, springs are there. I car seems to run very well at high timing. I have had timing as high as 38 - 42 degrees, and it run good and strong, but it has a very hard time starting with timing that high, the reason timing was that high is because it WON'T STAY SET from where intial timing was set at.
     
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  19. bbatch

    bbatch New Member

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    Is it possible that the shaft going to the distibuter is not staying in place and as the engine vibrates, the shaft is slowly turning inside the motor. That could explain the timing changing. It is kind of off the wall but is it possible?
     
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  20. hotcobra03

    hotcobra03 Active Member

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    If i was ur boss i would tell u ,open hood, start car set timing and idle and record it, mark dizzy with sharpie.drive car than recheck timing and idle and sharpie mark. Stop if you need to touch dizzy than i say its in their or engines not running right and but feels ok
     
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