1977 Chevy Silverado Timing mark

1977 CHEVROLET SILVERADO
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VEJA29
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1977 Chevy Silverado Four Wheel Drive Automatic

Why does the timing mark shift? I set it but it won't stay
Jan 27, 2010 at 12:23 PM
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SCOTTY DEE
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  • 592 POSTS
Is the rubber in the harmonic balancer coming loose? Are you using a fluid damper balancer? Are you able to get it close to 7 degrees before TDC?
Jan 27, 2010 at 12:43 PM
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RASMATAZ
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  • 75,988 POSTS
Could be coming from the vacuum advance unit/worn distributor cam lobe Hence: Dwell angle will change ignition timing-Ignition timing will not change dwell angle.
Jan 27, 2010 at 12:45 PM
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SCOTTY DEE
  • ✓Experienced Mechanic
  • 592 POSTS
Check for wear on the distributor gear, I prefer brass gears.
Jan 27, 2010 at 12:51 PM
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