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Thread: 1990 1500

  1. #11

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    ok i will do a compression check when I get home tomorow night and post up the resualts, thanks again for all the help

  2. #12

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    hey I just ran a compression test and all the cylinders were between 145-147 the number 8 cylinder was 30 any sugestions

  3. #13
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    That's bad news. The easiest thing to do first, is take off the valve cover & see if you have a weak or broken valve spring. If you're lucky this will be what it is cuz you can replace one or both fairly easy, (without taking the head off) but I'm afraid you won't be so lucky. I think you have either a burnt valve, broken rings, a bad head gasket, a cracked head, or a cracked piston. Which ever it is, you're going to have to pull the head off & have a look. No need to waste time diagnosing it any further cuz this one is going to be obvious. 30 psi is nothing. Gas needs a minimum of 90-100psi to fire correctly & contribute to anything near a smooth running engine.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  4. #14

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    hey I had the valve cover off while it was running , both rockers seemed to be moving same as all the other rockers , how else do you tell if the springs are bad

  5. #15
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    The rockers will be moving the same because they are controlled by the cam, lifters, & push rods.
    Did you hear one of the #8 springs clicking or clattering more than the other 6 on that side?
    If not then the best way to check is to turn the engine over by hand untill both #8 valves are closed (springs all the way up & relaxed) Take a piece of wood & push on the spring end of both rockers. Is one easier to push down than the other? Try comparing them to a couple of other springs on that side that are also relaxed (valves closed position) If you don't notice any difference then the springs are not weak or broken. (You can also do a visual on the springs for breakage)
    If this isn't a spring problem, then it's definitely inside & you're going to have to pull the head off.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  6. #16

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    ok I will try the springs in the morning and post up resualts hey do you think the valves could just be gummed up or stuck because the oil was really old the top of the valve covers were caked with old oil

  7. #17
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    They'd have to be stuck to the point that one of them wasn't closing in order to be losing 115psi out through the seat. Also if it was gummy valve stems or guides, I would be expecting to see the same issues with one or two of the other cylinders, but they are ALL even at 145-147. I'm still hopeing this is a broken spring, cuz it is the easiest & cheapest fix. Even if they both pass this test tomorrow, before you pull the head off, pull the 2 rockers off #8 & grab these 2 springs & rotate them around so you can see all sides of every coil. If your retainers are the "umbrella type" the top 3/8" of the spring could be broken & would be difficult to see. Also press down on the springs again without the rockers on there & see if one is weak. If this is a spring issue, you want to find it before you pull the head off.

    ** One other thing you can do is check the height of the springs/valve stems. Lay a straight edge across the tops & see if one is lower than the other. Something could have circulated through the engine & gotten stuck between the valve & the seat (doubtful, but it's possible)
    Last edited by stephan; 01-06-2011 at 10:57 PM.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol


  8. #18

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    ok i will do that in the morning and then post resaults , thanks again

  9. #19

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    Stephan's right on in checking the springs first. However with it having oil on the plug, unless the stem seal is bad (also possible), i'm thinking your problem is in the bottom end, unfortunately.

    Now, depending on what you're going to do with it, you can probably run it this way for a while. likely the farmer you got it from has been doing so. So if you don't have the time/money currently to pull the engine down, you can probably get by as is for a while. But still would at some point want to pull the engine and rebuild, or put in another used/rebuilt engine.
    Last edited by dualdj1; 01-07-2011 at 01:12 PM.
    1986 Chevy G20 Tow Rig - 5.7 TBI conversion
    1978 Mustang II King Cobra Road Racer - Holley 650, MSD 6AL, 5 speed, 10 point Roll Cage, 9" posi, fuel cell, custom interior.

  10. #20

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    yea that was what I was scared of, i am goin to go check the springs in just a little bit today also i will try and squirt a little oil down the cylinder to see if the compressio jumps up any, but i was goin to ask ive been looking around and I found a 1998 vorteck 5.7 , if I put my old manifold on it with my tbi would it bolt right in?

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