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how do i find TDC?

Discussion in 'The Garage' started by bigoltrux77, Jul 25, 2002.

  1. bigoltrux77

    bigoltrux77 1/2 ton status

    Jun 12, 2002
    Likes Received:
    Fort Polk, LA
    i have a 77 blazer with a 350. The main pulley doesnt have TDC marked on it so when i want to set the timeing (which sucks ass) i cant! Someone said i could do it at home by finding the number one spark plug and doing something. If someone knows how to find TDC, please give me a step by step description on how to do it...and what tools i need. PLease help soo..my trukc is slow and it burns gas. Thanks!
  2. ntaj*ep

    ntaj*ep 1/2 ton status

    Feb 4, 2002
    Likes Received:
    Evergreen state
    OK, not triing to be anything but helpful here, so bear with me here. #1 cylinder is on the drivers side of the engine its the first one in line. Take the #1 spark plug (or plugs) out, disconnect the coil wire, and put your thumb over the hole the #1 plug came out of. Now have a friend tap the ignition over slowly, when the cylinder is at TDC compression stroke you will feel the air hitting your thumb (or finger) it will be lots of air not a little. This will get you close, now put a piece of hanger or a long screw driver into the plug hole and with the help of your assistant turn the motor over by hand with a socket and ratchet (this is where having all the plugs out helps) when the screw driver, or what ever gets to the top of its travel it will stop and start going back down. You want it at the top most point. So you may need to turn the engine a little one way then a little the other till you get it perfect. Now as I said this will get you close to where you need to be.
    Mark the distrubiter #1 post all the way down to the base of the dist. So when the cap is removed the mark is still visible. Remove the dist. cap and see where the ign. rotor is pointed, if your close good if not then you will need to adjust it. If your close with the rotor then make a pionter somewhere on the front of the engine, and there is a timing tape that most part stores sells that will work. Just start the tape at the mark (being 0 degrees) and wrap it around the balancer. Or you could just make another mark on the balancer.
    Hope that helps you if you want more technical TDC info. I or someone else here I'm sure can help you. /forums/images/icons/grin.gif
  3. chevyracing

    chevyracing 1/2 ton status

    Sep 8, 2001
    Likes Received:
    The timing mark should be on the harmonic balancer, not the "main" pulley. The harmonic balancer is the big hunk of round iron behind the bottom pulley. It should have a line etched in it.
    The above described way is a good way to located top dead center or you could do it like this:

    find the plug wire that points at the number one cylinder. (furthest one forward on drivers side)

    make a pencil mark and the distrutor under the cap where the #1 plug wire attaches to cap.

    Take dist. cap off and see where the rotor is pointing. (that is the little thingy that spins inside the dist. cap.)

    Have the above mentioned friend turn over the engine until the rotor is pointing at the pencil mark.

    locate the etched line in the harmonic balancer.

    when the etched mark is at zero on the little scale pointer that is attached to the timing cover you have it.


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