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Timing problems

Discussion in 'Chevy Trucks' started by milwaukeevtwin, Nov 16, 2009.

  1. milwaukeevtwin

    milwaukeevtwin Senior Member
    Messages: 335

    I have an 89 2500 with a 5.7. I had the heads rebuilt and i put it all back together and i can not figure out how to get it timed properly. I set it to tdc and then dropped the distributor in pointing at number one piston and when it cranks, it cranks real freely. It popped a couple times and smoke came out of the carb, but will not start. Does it have automatic timing?Do i have to unplug something on the computer?Any suggestions? Please help.
    Thanks, Ron
     
  2. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    You need to make sure the engine is at TDC on the power stroke, not the exhaust stroke. When you put the distributor in, the rotor should point at the #1 spark plug wire on the ditributor cap. Not exactly sure what you meant by you pointed it at the #1 piston...??

    Once you get it fired, you have to disconnect the tan wire with black stripe located under the plastic cover on the passenger side firewall. That puts the ECM in base timing mode.
     
  3. chp

    chp Junior Member
    Messages: 21

    are you sure that you did not over tighten your lash settings on the rockers ,also the distributor rotor should be pointing at the # 1 spark plug wire on the cap. make sure that you are on TDC compression stroke.The computer controls spark timing but to set the timing corectly you have to disconnect the EST bypass connector and set the base timing to zero degrees
     
  4. milwaukeevtwin

    milwaukeevtwin Senior Member
    Messages: 335

    Help

    I torqued the rockers down to what the book said. Maybe i miss read the book. It sounds like it does not even have compression when it cranks. Would this cause that? It has compression. I bump started it and got it close. Then we stuck a screw driver in the spark plug hole to feel the piston. That is how we got it to top dead center. Both valves are about at the same when this is at that point. I think the first one is the exhaust. Does anybody know the correct torque specs on the rockers?
     
  5. chp

    chp Junior Member
    Messages: 21

    If they are factory rockers the correct spec is adjust the the nut until there is zero lash at the pushrod and then tighten another 3/4 turn. To find TDC easily remove #1 plug stick your finger over the hole and bump the engine over until compression is felt, Then line up timing mark on balancer with zero degrees on degree indicator on timing chain cover. make sure that you turn engine clockwise as viewed from front of engine,then you can set 1/2 of the valves. then set the engine to TDC on #6 and set the rest of the valves
     
  6. milwaukeevtwin

    milwaukeevtwin Senior Member
    Messages: 335

    Thanks, I bet this is the problem. After reading this i know they are set to tight. I torqued them all to the same spec and i want to say they were 35 foot pounds. I am sure this is the problem. Thanks, for all the help. i will let you guy's know Friday.
     
  7. cubicinches

    cubicinches PlowSite.com Addict
    Messages: 1,412

    That would be your problem....

    The valvetrain is adjustable. You can't just torque the rockers down.

    Here you go...

    Turn the engine over until the #1 cylinder is at TDC on the compression stroke. Do this by turning the engine over until you see the #1 intake valve open fully then start to close. As it starts to close, watch for the mark on the harmonic balancer to come to TDC on the timing pointer and stop there. Then adjust the following valves on these cylinders:

    INTAKE - 1, 2, 5, 7
    EXHAUST - 1, 3, 4, 8

    After you adjust those, turn the engine one full revolution until the mark on the balancer comes back to TDC on the timing pointer again. This is TDC on the compression stroke for the #6 cylinder. Then adjust the following valves on these cylinders:

    INTAKE - 3, 4, 6, 8
    EXHAUST - 2, 5, 6, 7

    To adjust the valve, start by making sure the rocker nut is backed off enough that there is some lash. Then slowly tighten the nut while turning the pushrod between your fingers. As soon as resistance is felt on the pushrod, and thereis zero lash at the rocker,stop. Then tighten the nut 1/2 - 3/4 of a turn further.


    Good luck, let us know how you make out.
     
  8. chp

    chp Junior Member
    Messages: 21

    I checked my GM service manual 5.0L - 5.7L. Engines are one turn down after zero lash& 7.4 L are 3/4 turn after zero lash
     
  9. milwaukeevtwin

    milwaukeevtwin Senior Member
    Messages: 335

    Thanks, For the HELP

    I did what you guys told me to do and it took about an hour and two cranks. The truck started up and it took awhile to get the smoke to clear and it runs like a champ. I just want to go back and torque the heads one more time and fine adjust the timing. Off to the breaks now. Thanks guys i really appreciate all the help. I was stumped. This was my first time doing heads and besides the rockers it turned out good.purplebou:redbounce
    Ron
     
  10. chp

    chp Junior Member
    Messages: 21

    There is no need to retorque the heads unless you used steel shim style gaskets. Modern composite gaskets are fine with the initial torque and do not require any additional torquing.
     
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    However re-torquing the intake and exhaust manifolds is a good idea after a few heat cycles.
     
  12. milwaukeevtwin

    milwaukeevtwin Senior Member
    Messages: 335

    Thanks, Guy's

    The guy that rebuilt the head suggested to re torque the heads after it heated up. I am going to go back and check the intake and exhaust. The truck has been sitting for a while and it has whit smoke still coming out the exhaust. Like strait moisture. It has gotten better. It does not smell sweet or stink like oil. I hope it goes away.
    Thanks, Ron