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Timing gear marks

Discussion in 'GM Powertrain' started by bigbluesub, Feb 7, 2011.

  1. bigbluesub

    bigbluesub Rockstar

    Greetings all, I am a little perplexed. When I pulled the timing cover off, the two dots were at 12:00. Now that I am putting it back together, it seems that for proper timing it has to go back that way. I thought the two timing dots had to meet for proper timing? When i put it together that way I was not getting any compression out of #1. So then i turned the crank until it had the #1 piston up, turned the cam until the dot was at 12:00 then it had compression. Any input would be appreciated.
     
  2. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    I don't remember if you have to time it with the two dots pointing at each other or if they both have to be pointing up. Here's the crux: once you rotate the crank once, the dots will be pointing at each other, or both pointing up. When you turn the crank another full turn, they both point in the opposite position. The cam to crank gear ratio is 2:1, which means both occur in operation. The key difference is if you line it up backwards to what the rebuild manual says, when you install the distributor, you could be 180 degrees out of time with the rest of the engine. Consult your Haynes manual, it'll tell you, and then confuse you with roughly what I just said.
     
  3. stephan

    stephan Rockstar 4 Years 5000 Posts

    BigBlue, The timing mark on the crank sprocket needs to be at 12 oclock at the same time as the mark on the cam sprocket is at 6 oclock for correct cam timing.
    #1 piston at TDC, crank mark is at 12 oclock. Then move your cam untill the mark on the cam sprocket is at 6 oclock pointing at the mark on the crank sprocket.

    *If you have moved your ignition distributor during all of this, then you will have to move it back after you have done the cam timing correctly
     
    Last edited: Feb 7, 2011

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