5.3L Head Removal (2002 Tahoe)

Discussion in 'Engine & Drivetrain' started by Larryjb, Dec 8, 2018.

  1. Larryjb

    Larryjb Full Access Member

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    So many of you have helped me in many ways, so I thought I'd return the favour for anyone thinking about doing their own heads.

    I made this check list so that I wouldn't forget to reconnect or install any bolts. I don't think I forgot anything on this. This is not a guide for the job. Use a service manual if you've never done this before.

    I work slowly. Removing the heads took me about 2 days solid. However, I was bagging all parts and making notes. Installation took about 3-4 days solid because I was cleaning all surfaces. I also cleaned the piston tops using Gasket Clean and a razor. This worked really well. I didn't get them perfect, but it was very close. Also, I replaced the water pump at the same time.
     

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  2. swathdiver

    swathdiver Full Access Member

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    Thanks for taking the time to write this!
     
  3. MrBalll

    MrBalll Full Access Member

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    Nice little guide. Thanks for writing it up and posting for us.
     
  4. Larryjb

    Larryjb Full Access Member

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    It's running smooth as silk now. My scantool is showing that the O2 sensors seem a little lazy, and I think my PCV system is leaking a little air. I plan to install a catch can as soon as I can get the right hoses. Also, the downstream O2 sensors are running at about 750 to 800 mV. From what I understand, that indicates that the exhaust gases are still a little on the rich side and the catalytic converter is burning off the remaining hydrocarbons in the exhaust which, in turn, lowers the O2. It's my understanding that the downstream O2 sensors should be closer to 500 or 600 mV. Also, the upstream O2 sensors switch barely between 800 and 200 mV. I have new O2 sensors on order and will install them in the coming weeks.

    The machine shop seems to have done a very nice job with the heads.
     
  5. Larryjb

    Larryjb Full Access Member

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    One of the biggest challenges I had was determining TDC for torqueing the rockers. I could have rotated each rocker in turn so that each was off the cam lobe and torqued them. However, there is a procedure in the factory service manual that shows you to set the crank to TDC, then you torque a specified number of rockers (see service manual). At TDC, 8 rockers are off the cam lobes. Then you rotate the crank 360° and torque the remaining rockers. The trick is knowing exactly where TDC is when the head is installed.

    The best way is to mark TDC on the crank pulley before you install the head so you will know what position this is. If you're like me, you don't think to do so and make extra work for yourself. So, I decided to do some thinking, and this method worked:

    It is easy to see then the intake and exhaust valves are beginning to open or close. So, knowing the firing order: 1, 8, 7, 2, 6, 5, 4, and 3, you can easily infer TDC. Rotate the engine so that the cylinder 1 rocker just begins to open, but the exhaust rocker does not. This will be the intake stroke. Once the intake valve begins to close, the piston will be at the bottom of the stroke and beginning to rise during the compression stroke. You can confirm this when you observe that the exhaust rocker also remains closed.

    Now, very soon after this point, the piston will be in TDC. How will you know? Look at the other rockers just before the firing of piston 1. At TDC, piston 4 will have just fired and been on its way down. It's valves will still be shut. Cylinder 6 will be at the top of it's exhaust stroke.
    Cylinder 1: beginning combustion stroke; intake closed, exhaust closed
    Cylinder 8: compression stroke; intake closed, exhaust closed
    Cylinder 7: end of intake stroke; intake switching from open to closed, exhaust closed
    Cylinder 2: intake stroke; intake open, exhaust closed
    Cylinder 6: end of exhaust stroke; intake switching from open to closed, exhaust switching from open to closed
    Cylinder 5: exhaust stroke; intake closed, exhaust open
    Cylinder 4: end of combustion stroke; intake closed, exhaust switching from closed to open
    Cylinder 3: during combustion stroke; intake closed, exhaust closed

    From this information, you can see that intake rockers 1, 8, 5, 4, and 3 and exhaust rockers 1, 8, 7, 2, and 3 are definitely closed and safe to torque. The service manual instructs you to torque intake rockers 1, 3, 4, and 5 and exhaust rockers 1, 2, 7, and 8. It should be safe to torque intake #8 and exhaust #3 as well, but I stayed with the service manual instructions. The key here is understanding when you are at TDC:

    Look at the switching rockers. As soon as 7I, 6I, 6E, and 4E begin switching, you are at TDC.

    Because 1I, 4I, and 3I are all closed before and after the next firing order, there is absolutely no danger of torqueing these down in the "open" position. If you see cylinder #6I just closing, #5I MUST be closed, so that is safe to torque also.

    It would probably be enough to note when cylinder 6 I and E are switching together. No other rockers switch at the same time.

    I don't know if this helps anyone. I suppose I could have peeked inside a spark plug hole as well, but that's kind of hard to do when working alone.
     
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