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Valve knock on odd bank

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jay73K20, Jun 18, 2002.

  1. Jay73K20

    Jay73K20 Registered Member

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    Last night I pulled the valve cover off and adjusted all of the valves 3/4 of a turn passed the noise with the motor running. I don't believe it is valve lash. I have ceramic-coated headers and the #5 primary tube is dulling badly. I think that cylinder is to lean because the truck is getting 12MPG and it has good power. I also checked spark and it is fine. What do you guys think, flat cam lobe, valve guides to tight? I'm going to pull the spark plug tonight to asset how it is burning and the do a compression test. I figure if I get higher cranking compression then any other cylinder my cam lobe is flatting out. Thanks in advance for any suggestions.
     
  2. 95 Silverado

    95 Silverado 1/2 ton status

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    what valve springs are you using? if the cam has more lift than the springs can handle you could be binding a valve spring. check the inside of the valve cover for marks where a rocker arm could be hitting it. with the valve cover off check the push rod travel, you should be able to see if one of the pushrods isn't moving as far as the rest, also if the head has pressed in studs sometimes they will pull out and you will lose valve lift on that cylinder. a couple of things to check. good luck
     
  3. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    1/2 turn past clicking is what I've been told. Put a mic on the lobes in question and measure the lift in retrospect to the good ones. Do a compression test too.
     
  4. Jay73K20

    Jay73K20 Registered Member

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    Well I pulled the spark plug out and it looked a little leaner then the rest. Did a compression check and 1,3,4,6-8 was 195-205 dry, 2 was 180 dry 190 oil, 5 was 170 dry 230 oil. Cam lift is .447 Int, .462 Ext, which should be underneath coil bind. I've heard .475 - .490 depending on source for coil bind. I'm going to pull the valve cover tonight to look for irregularities. I don't have a mic or I would mic it. Thanks for the replies.
     
  5. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Sounds like you have the same cam as I do. 210/218 duration with .447/.462 lift. I just used the stock springs in my vortecs. They're meant to run on a roller cam engine, which has higher lift than the traditional hydraulic motors. I've rapped mine up to 4,500 so far and it worked like a charm. I have a plug or two that looks a little different from the rest. As long as there are greyish brown deposits on there, I wouldn't lose to much sleep.
     

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