Timing jumping

Discussion in 'Technical' started by adam 72, Sep 28, 2020.

  1. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    I'm about to pick back up a project I had to stop a few years back. I recently dropped in a rebuilt 200. We got it started and all was going well till we turned it off and turned it on again. The car wouldnt start. We had to turn the distributor around and it would fired up again. Tried a points, pertronix and duraspark 2 distributor. Similar issues

    Where should I start looking? I suspect the timing chain (dual timing chain if memory serves me). Any other places I should check?

    Hopefully I get her home this month

    Thanks again
     
  2. ike72com

    ike72com Member

    Joined:
    Sep 22, 2019
    Messages:
    408
    Likes Received:
    247
    Trophy Points:
    111
    Garage:
    1
    Location:
    Charleston SC
    Vehicle:
    1972 Comet, 70 mustang, F250 and F100
    1. Think you should find/check TDC. Reinstall distributor and check plug wire.

    2. Could also be being a rebuilt motor your valve adjustment is out of whack.

    3. You stated engine did start. How did it run? Did it backfire or anything unusual causing it to quit.

    Starting a new motor or after cam swap is alway nerve wrecking for me. CHECK and Recheck wires.

    Ohhh and check for fuel. Empty tank got me once!
     
  3. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    It would start fine. Never drove it. Idle was smooth. Once it was shut off it was almost 180 degrees off and had a nice backfire. I will verify TDC again, but we did that with each different distributor.

    We checked fuel... Only cause it was on the floor from a cracked line we addressed quickly
     
  4. Jaybee

    Jaybee Member

    Joined:
    Feb 17, 2019
    Messages:
    455
    Likes Received:
    214
    Trophy Points:
    117
    Location:
    Hampton Roads, VA
    Vehicle:
    1974 Maverick
    Sure sounds like it skipped the timing chain.
     
  5. ike72com

    ike72com Member

    Joined:
    Sep 22, 2019
    Messages:
    408
    Likes Received:
    247
    Trophy Points:
    111
    Garage:
    1
    Location:
    Charleston SC
    Vehicle:
    1972 Comet, 70 mustang, F250 and F100
    I,ve never experienced a skipped timing chain before. Heard its caused from slack from chain being worn/stretched

    Your motor is rebuilt. Shouldn't chain be tight?
     
    mojo likes this.
  6. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    Yeah thats why we never took the chain off. Its a dual roller chain. I didn't do the rebuild, maybe I should verify its the right chain? Any way to check it without pulling it?
     
  7. 71gold

    71gold Frank Cooper Supporting Member

    Joined:
    Apr 9, 2002
    Messages:
    26,531
    Likes Received:
    2,899
    Trophy Points:
    978
    Garage:
    1
    Location:
    MACON,GA.
    Vehicle:
    '73 Grabber
    did you check #1 on compression stroke?
     
  8. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    Its been so long, I honestly dont remember. Would I fire up if it wasn't on the compression stroke? It started multiple times, it just had to be re timed each time
     
  9. Krazy Comet

    Krazy Comet Tom

    Joined:
    Sep 13, 2012
    Messages:
    7,673
    Likes Received:
    2,407
    Trophy Points:
    531
    Garage:
    1
    Location:
    Chesapeake VA
    Vehicle:
    1972 Comet GT clone 306 . 1969 Fairlane Cobra 428CJ 1988 T-Bird awaiting 331 ..
    No it doesn't, skip on timing chain skews valve timing, generally rendering engine a big lump. If timing chain slips more than a couple teeth, valve timing is off enough that engine won't run at all, reguardless of dist setting. It isn't likely ign timing was 180* out unless roll pin in dist gear is twisted off or the rotor is slipping.
     
    Last edited: Sep 29, 2020
    RMiller likes this.
  10. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    I was reading about the roll pin. At the time, I had no idea that was even a thing. I found these last night.
     

    Attached Files:

  11. mojo

    mojo "Everett"- Senior Citizen Supporting Member

    Joined:
    Jul 20, 2009
    Messages:
    5,270
    Likes Received:
    833
    Trophy Points:
    513
    Garage:
    1
    Location:
    Chicago
    Vehicle:
    73 Comet GT-302 4bl
    Looking at the pic, I don't see what you are referring " You found what last night"?
     
  12. adam 72

    adam 72 Member

    Joined:
    Nov 13, 2011
    Messages:
    326
    Likes Received:
    2
    Trophy Points:
    77
    Location:
    New Mexico
    Vehicle:
    1972 maverick
    Just a photo with the timing chain. I it doesnt appear to be loose. I know its just a photo, but it's been a while
     
  13. ike72com

    ike72com Member

    Joined:
    Sep 22, 2019
    Messages:
    408
    Likes Received:
    247
    Trophy Points:
    111
    Garage:
    1
    Location:
    Charleston SC
    Vehicle:
    1972 Comet, 70 mustang, F250 and F100
     
  14. ike72com

    ike72com Member

    Joined:
    Sep 22, 2019
    Messages:
    408
    Likes Received:
    247
    Trophy Points:
    111
    Garage:
    1
    Location:
    Charleston SC
    Vehicle:
    1972 Comet, 70 mustang, F250 and F100
    Okay....let us help you.

    And recheck your fire order, Recheck plug wires. Load fuel bowl with fuel and go for it.
     
  15. Krazy Comet

    Krazy Comet Tom

    Joined:
    Sep 13, 2012
    Messages:
    7,673
    Likes Received:
    2,407
    Trophy Points:
    531
    Garage:
    1
    Location:
    Chesapeake VA
    Vehicle:
    1972 Comet GT clone 306 . 1969 Fairlane Cobra 428CJ 1988 T-Bird awaiting 331 ..
    Chasing the timing chain is going to be as fruitful as.... :deadhorse:

    If chain or timing gear slips, BOTH valve & ignition timing are skewed.

    Worse case is maybe the gear on cam has chipped or missing tooth. Possibly there is a mismatch in size of dist gear with cam or again, roll pin sheared. Verify rotor isn't slipping.

    As suggested verify TDC by compression. I'll bet that never changes.
     

Share This Page