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rocker arm tap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by NoShow84, Apr 22, 2002.

  1. NoShow84

    NoShow84 Registered Member

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    My buddy has an 85 Blazer with a high output 305, his rocker arms started tapping, we adjusted them, took it out for a drive, about 3 miles down the road, they start tapping again. We retighten them, and the whole process starts over. What could be the problem. Thanks for your help.
     
  2. TopOff

    TopOff 1/2 ton status

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    The studs for the rockers could be coming out. Do you have higer rate valve springs?

    Could also be lazy lifters. I know this is my problem. I have three tapping. If I tighten them, then I lose compression on the cylinder when it is cold. Then when the oil heats up, the lifters leak and I get valve tap...

    Good luck

    TO
     
  3. chevyracing

    chevyracing 1/2 ton status

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    adjusting nuts could be worn out so they will not stay locked, oil too thin, oil pressure too low, or gremlins.

    John
     
  4. NoShow84

    NoShow84 Registered Member

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    no he dosen't have high rate springs and what do you mean by a "lazy" lifter never herd that before
     
  5. weisel

    weisel 1/2 ton status

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    I had a buddy's engine do that. We were constantly adjusting the rocker arm nuts until the dang thing wouldn't run. Turns out the lobs on the cam wore down to nothing which can't lift the lifters and the valves stopped opening. I sure don't hope this on you though. I would check the nuts first like said before. I have seen many of those nuts worn out and work themselves off of the stud.
     
  6. TopOff

    TopOff 1/2 ton status

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    My hydraulic lifters are not holding pressure. Hence, only the mechanical part of the lifter is lifting the valve. When trying to tighten the rockers for the little bit of pressure (no tap 1/2 turn tighter), there isn't any as these lifters are now solid lifters. So when I go 1/2 turn tighter, the valve stays open.

    I have been told this is a "lazy lifter". Basically, I got the lifters "new in the box". Of course the lifters and box had been sitting for couple of years.

    So I need to replace the lifters. Then I will get into all the ... while I'm in there... replace the cam, replace the lifter rods.. etc etc.

    Good luck.

    Do you know specifically which lifters are having the problems? Can you see the valve opening when rotating the engine?
    After adjusting, check cylinder pressure (this was my problem too tight a valve and I got no cylinder pressure). I back the valve off, and I get cylinder pressure with a valve tap.
     

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