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Valve Clatter

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by woodpecker, Dec 19, 2000.

  1. woodpecker

    woodpecker Registered Member

    Joined:
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    Location:
    Mount Vernon, WA
    Hey Guys,

    I've noticed lately that sometimes I get a loud valve clatter when pulling mild slopes at 55 mph. I've toyed around with diff. octanes, and don't seem to notice a correlation between reg-unleaded, super, and the mid-range stuff. I'll drive the same section of freeway, and sometimes it'll sound like a damn diesel, other times, it'll purr like a kitten. The engine is the original 305 with 106K miles. From what I've been reading, I'm hoping like hell to get a good 180-200K miles before having to drop a new engine in. Could this just be an indicator of the need for a tune-up? Also, I hear a noticeable tick (lifter noise?) at warm up; about 100 degrees F on the coolant gauge. Noise lasts for a few seconds, but then goes away. As you can tell, I'm not the most adept backyard mechanic. Could the two be related?

    Love any input.
     
  2. Heath-La. 89GMC

    Heath-La. 89GMC 1/2 ton status

    Joined:
    Feb 18, 2000
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    Location:
    Monroe, Louisiana
    That ticking you hear is an exhaust leak. A small one will go away when the engine warms up. As long as it only does it when you first start it.. its probably no big problem. Just dont let it get out of hand.. it can possibly cause problems. Try to tighten your exhaust mainifold bolts. You might even want to change gaskets. ($3 or so at Auto Zone) As far as the valve rattling.. that sounds like a fuel problem to me... try putting the highest octane gas you can in there AND some kind of fuel additive (like Hot104 or something) If that doesnt help.. your valves probably need adjusting. If your not very knowledgable about engines and repair.. you might want to get some help with this. Hope this helps...
     
  3. Channing74

    Channing74 Registered Member

    Joined:
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    Location:
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    What year model? some years had those dang plastic coated timing gear sets. could be that the plastic is breaking off and causing slack in the chain. just a thought.....

    Bigger Is Better
    Channing74
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
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    Location:
    Atlanta
    Try some STP in the silver bottle listed as Fuel injector cleaner. what your hearing is detonation/ping. it's bad and if it's left to do it it can and will burn holes through the piston or valves. Carbon build up often causes it. Could need to go to a higher heat range plug. The STP I have had very good luck with it helping.
    Other causes of this would be timming issues. pull the cap and rotor and check the weights to see if the swing free. Sometimes the inner shaft that those weights control will gum up and cause a problem like your having. To much timing advance and also cause the issue.
    Another thing to check is make sure the Thermac door is working correctly. That's the little diverter flap on the air cleaner that makes it it suck hot air off the exhaust manifold when cold. it should pull cold air when warm or it can cause issues like your having.
    You can also try some top end engine cleaner to clear out the carbon. It's about $8 form the dealer. Basicly you let the stuff get sucked in a vacume port like the PCV and it breaks down the carbon. I wasn't a believer in the stuff till it fixed a stuck valve in my work van.

    Diging it in the dirt with my K5's
    Grim-Reaper
    http://grimsk5s.coloradok5.com/
     

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