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Really need to find TDC?

This is a discussion on Really need to find TDC? within the Internal Engine forums, part of the LSx Technical Help Section category; Hey guys, I checked the rockers and pushrods as a potential source of a knock in the engine. They look ...

  1. #1
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    Really need to find TDC?

    Hey guys,

    I checked the rockers and pushrods as a potential source of a knock in the engine. They look fine, but putting everything back together is a bit more complicated than I thought. The Haynes manual claims you need to get certain pistons to TDC as you re-tightening certain rockers.

    Is this really necessary? The procedure they quote for finding TDC involves removing the plugs and sticking a screwdriver into the cylinder, then manually rotating the crackshaft and watching for the screwdriver to get to the position of maximum sticking out. Beyond the fact that there's a big frickin wheel well and power brake assist making it impossible to get a screwdriver into the cylinder, it just seems like a lot of extra work.

    Does anyone who has replaced their rockers have any feedback?

    Thanks,
    Matt

  2. #2
    Member squee's Avatar
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    Yea, I'm pretty sure its necessary to adjust them properly.

  3. #3
    Veteran 0rion's Avatar
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    I can tell you how I did it which probably isn't right but it worked for me. I just turned the motor by hand and watched the pushrod. Once the pushrod showed that the valve was closed I torqued the rocker down. That's just how I did it.

  4. #4
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    That's a good idea. I assume the only reason the pistons have to be in a certain position is to guarantee the valves are closed when the rockers are tightened. Is that correct? If so, any time during the compression stroke or power stroke should be ok, yes?

    Thanks,
    Matt

  5. #5
    TunedbyFrost.com Tuner Frost's Avatar
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    Quote Originally Posted by matt100psi View Post
    That's a good idea. I assume the only reason the pistons have to be in a certain position is to guarantee the valves are closed when the rockers are tightened. Is that correct?...


    Yup.

  6. #6
    Senior Member mrr23's Avatar
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    what i do is slowly tighten them all down. then, torque them all down to 22 ft-lbs. then turn the motor over one revolution and recheck the torque. never had any issue.

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    I did them one at a time just to be safe, making sure each piston was right around the compression/power transition when I tightened it down. Seems to have worked. I'm sure it was overkill, but I didn't want to screw up something that important.

    Anyway, the rods/rockers weren't causing the knocking I heard. Listening with a stethoscope, it sounds like it's on that side of the engine (odd cylinders). Anyone have other ideas as to what it might be? I've seen a mention or two about the lifters, but I'm not sure what about a lifter can go bad. I guess it could be the valves, but I don't think they're adjustable anyway. What experiences do people have with knocking?

    Thanks,
    Matt

  8. #8
    Member squee's Avatar
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    I'm pretty sure a lifter could go bad if you over tightened the rocker.

  9. #9
    Senior Member mrr23's Avatar
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    Quote Originally Posted by squee View Post
    I'm pretty sure a lifter could go bad if you over tightened the rocker.
    the rockers being stock, you can't over tighten them and cause a lifter failure. stock rockers are not adjustable.

  10. #10
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    Kind of inconsequential as the knocking existed before I or any mechanic touched the rockers. What does it mean for a lifter to "go bad"?

    Thanks,
    Matt

  11. #11
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    The rockers on a stock LS1 are not adjustable. Just torque them all down to 22 lb/ft and then rotate the crank 360 degrees and retorque, just as someone said earlier.

  12. #12
    Member 99transamC/FIA's Avatar
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    Ditto for MattD.
    tighten them all rotate 360* and retighten.

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