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Timing question

Discussion in 'Bay Tech Clinic' started by kr.au, Nov 1, 2021.

  1. kr.au

    kr.au New Member

    Messages:
    25
    Location:
    Brisbane
    Have just finished the complete rebuild and install of the motor in my restoration project - motor is a 2 litre (CJ code) with auto trans from a 76 camper (now in a '75 single cab). It starts and runs - rough as guts but bloody happy that everything seems to be basically working.

    It's almost stock except for a petronix ignition to replace the points. Dual carb.

    What is the right timing for this motor?

    The Bentleys manual I have doesn't cover CJ motors. It does say 73-75 dual carb and fuel injection with automatic transmission should be 5 degrees after TDC with vacuum hose on at 900-100 RPM (Engine Code CD, AW or ED). Would my CJ be the same?

    Follow up question (just out of curiosity) - the engine number on the fan cowling is clear, but the number on the case seems to have been over stamped with a new number. You can still make out the CJ - but is has 'N7918481' stamped over it. Any idea what that means?

    Engine.jpg Case engine code.jpg
     
  2. cbus

    cbus Well-Known Member

    Messages:
    13,562
    Location:
    sunshine coast
    The case has been given a new number.
    Maybe due to stolen vehicle or rebuild and no prior records.?

    The atdc setting only applies if you have a dual vac distributor.
    Set to 7.5 BTDC with NO hoses connected.
    This should get be you between 28 and 32 degrees at about 3500 rpm or max advance shown.
    With vac line/s ON you should show max 42-44 BTDC blipping throttle at revs to get max advance on mechanical and vac.

    Petronix can give scattered timing.
    If that happens , ensure you have shielded HT leads.
    Either carbon core or spiral wound.
    Not wire core as per stock.

    New engine...
    Ensure you do cam bed in proceedure.

    Then rings on road within 100km.
     
    Last edited: Nov 1, 2021
    Wiz, Wayne murray and oldman like this.
  3. kr.au

    kr.au New Member

    Messages:
    25
    Location:
    Brisbane
    Thanks @cbus!

    Re cam break bed in - will run at 2000rpm for 20 mins. Is that what you mean?

    What do yo mean by 'rings on road within 100km"?
     
  4. oldman

    oldman Super Moderator Staff Member

    Messages:
    10,931
    Location:
    Avalon Beach NSW
    “Rings on road” is driving under various loads and speeds……
    Cheers,
    Mark
     
  5. cbus

    cbus Well-Known Member

    Messages:
    13,562
    Location:
    sunshine coast
    Yep for cam.

    For rings, idea is to find a hill and with engine up to temp and about 80 kms on motor , in 3rd gear floor throttle between 2000 up to 3500 rpm ( ish) and back off . Repeat a few times.
    Idea is to bed in rings while hone marks are still fresh.
    Oil change after that.
    Needs to be hot and under load to do this.
    Gives a better seal.

    After that as per Marks suggestion.
     
  6. kr.au

    kr.au New Member

    Messages:
    25
    Location:
    Brisbane
    thanks again @cbus. Will do.
     
  7. cbus

    cbus Well-Known Member

    Messages:
    13,562
    Location:
    sunshine coast
    I should add...
    Don't overheat engine either.

    Allow something like 20- 30 seconds at light throttle between bursts of full throttle for things to cool down a bit before repeating.
     

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