valve adjustment?

Discussion in 'GM Powertrain' started by sparky09, Feb 16, 2009.

  1. sparky09

    sparky09 New Member

    allright, i have a question about the valve adjustment on my truck...
    it is a 92 reg cab long bed with a 355 (.030 over 350)
    tore it down to replace the headgaskets and pulled the heads, and intake manifold, while replacing the gaskets i noticed the clip that holds the hydraulic lifter together had come apart.
    so i got a new set of lifters and installed them, adjusted the valves per service manual. however i did not prime the engine with oil beforehand. got it back together and fired it up and seems to run like crap...
    my question is, since i did not prime the engine, do i need to readjust the valves and see how that does? i'm sure the timing is set, i'm kinda lost on this and need the truck back asap... thanks for reading and replies.
  2. KirkW

    KirkW Rockstar

    I've never been very successful adjusting the valves per the factory service manual. I've always had much better results adjusting it while the engine is running. It's somewhat a pain because you have to unplug a bunch of wires and hoses to get the valve covers off, then plug in enough wires and hoses to get the engine to start and run, yet still provide clearance to reach the adjusting nuts.

    Plus, you should install little clips on the oil squirt holes to keep oil from spritzing out.

    The trick is to turn the adjusting nut s-l-o-w-l-y. Turn the nut out s-l-o-w-l-y until you hear a definite clatter from that valve (it's unmistakable). Then s-l-o-w-l-y turn the nut back in 3/4 (or is it 1?) turn. If you turn the nut in too fast then the lifter won't bleed down and it will clatter at any position.

    YouTube has a number of home videos of the technique. It works quite well and is accurate.

    That being said, I don't know if it will fix your truck but at least you've eliminated a variable.
    Last edited: Feb 17, 2009
  3. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    +1 on adjusting the valves with the motor running vs. using the manual. I've never actually even done it per the instructions in the manual.
  4. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Kirk has the right idea, but it's backwards. You need to loosen the nut until it starts to clatter then slowly tighten it back until the clatter stops and then tighten and additional 3/4 turn.

    And as he said, find some rocker clips at your local parts store to put over the top of the rockers to keep the oil from squirting all over the place while you are doing it.

    Good luck.
  5. sparky09

    sparky09 New Member

    ok, i readjusted the valves, did not run while adjusting due to lack of oil control tools (can't make a mess of oil everywhere as i am not at my garage). got the valves adjusted and put back together and idles great. my only new concern is i think i have a timing issue, it idles great but while driving underload it doesn't have alot of power. also if i try to kick it down a gear and speed up it just backfires and boggs down... sound like a timing issue?
  6. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    That sounds like a timing issue to me. You say you have a 355 in it, is it carbed or still TBI?
  7. KirkW

    KirkW Rockstar

    Doh! I just re-edited my post. That'll learn me from posting late at night....
  8. sparky09

    sparky09 New Member

    it is tbi. its a .030 over rebuilt 350.
  9. GaryL

    GaryL Epic Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Try resetting the timing. There is a timing advance wire you have to unplug (brown wire near the distributor on the firewall with a plug connector.) Start it up with the wire unplugged and set timing to 0 degrees BTDC. Turn off engine. Plug wire back in and computer takes over. See if this gets you back in shape.

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