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adjusting valve lash... - this one works

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by solowookie, Apr 1, 2002.

  1. solowookie

    solowookie 1/2 ton status

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    ok guys - I understand how to adjust the valve lash on a hydralic cam, but what I don't understand is why you adjust them, and some will be on and some will be off & make noise when you run it.

    the only real good way I've found to adjust these and get them all so they aren't loose is while it's idling. I'm assuming there has got to be a better way to do this while I'm putting it together. do I take each cylender & watch the lifter, and adjust it while it is all the way down or what?
     
  2. UseYourBlinker

    UseYourBlinker 1 ton status

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    3rd times a charm...(LOL....at the other posts)
     
  3. HarryH3

    HarryH3 1 ton status Author

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    The lash has to be adjusted while the lifter is on the base circle of the cam. If it's sitting on any raised part of the lobe then the valve geometry isn't correct while you adjust out the free play. The valve is closed while you're making the adjustment, so you need to have the lifter on the part of the cam that would have the valve in that closed position.

    Suppose the actual lift of the cam lobe is 1/4-inch and the lifter is sitting at the top of a lobe while you adjust out the slack in the valve train for that particular valve. Now when the cam rotates so that the lifter is sitting on the base circle, you have 1/4-inch of slop in the valvetrain. /forums/images/icons/frown.gif
     
  4. solowookie

    solowookie 1/2 ton status

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    so how do I determine the valve is closed? watch the lifter until it begins to rise, and then back it off again? (assuming this is probably the easiest way)
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Jeff,

    Set the motor at number 1 TDC.
    With the engine at #1 TDC you can adjust:

    Exhaust...1,3,4,8
    Intake...1,2,5,7

    Once those have been set rotate the motor one full turn (it should be at #6 TDC now)

    adjust these valves.

    Exhaust...2,5,6,7
    Intake...3,4,6,8

    Hope that helps

    Rene
     
  6. solowookie

    solowookie 1/2 ton status

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    no Rene that doesn't help because it just sound TO STINKING EASY! /forums/images/icons/crazy.gif/forums/images/icons/mad.gif (man I wish I'd have known this on JMT... LOL)

    BTW remind me how to watch the rockers and figure out I'm on TDC compression stroke (where distributor will not be 180 out)
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you don't have the timing cover on it's really easy. Both timing dots at the 12 o'clock is #1 TDC.

    If the crank dot is at 12 o'clock and the cam dot is at 6 o'clock the motor is at #6 TDC.

    Rene
     
  8. solowookie

    solowookie 1/2 ton status

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    yea, but it is 4 stroke so how do I know when I'm on the compression stroke?I'm going to hit TCD 4 times correct? each time I'm TDC my valves can be different depending on what that stroke is doing...

    so am I TDC on compression stroke, power stroker etc.? how do I find TDC for the compression stroke so I can install my distributor? (yea I have my timing cover on & know how to line up the dots)
     
  9. solowookie

    solowookie 1/2 ton status

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    Tim helped me figure this out in a chat session - second night in a row he's helped me get something solved;

    Tim says:
    okay, intake comes open right before piston comes to top, goes down, sucks air in, that's your intake stroke
    piston gets just past the bottom, intake valve closes (both are now closed) compression stroke starts
    plug fires mixture, piston goes down again with both valves closed, that's your power stroke
    right before the piston gets to the bottom, exhaust valve opens, piston goes up, pushing exhaust gasses out, and it starts over again
    Jeff says:
    so piston fires at end of compression stroke -
    Tim says:
    yes
    Jeff says
    so when the 2 valves close it won't be TDC - piston will be down & not up - when it lines up with timing mark end of compression / beginning of power which is where my plug fires, and then I set my distributor for about 5:00
    Tim says:
    yes, that's how i put the distributor in
    Tim says:
    you can make ANY terminal you wish be #1 on the cap as long as you do them in the right order and put the rotor in accordingly
    Tim says:
    the factory uses 5 o'clock so that's what I do too
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    No, you'll either be on #1 or #6 when you timing marks line up.

    First part of the stroke ends at BDC, (intake) stroke 2 is compression and ends at TDC #1, next part is the power stroke and that ends at BDC. The last of the '4' strokes is the exhaust and it ends at TDC again. 4 strokes is 2 revolutions.

    What is assembled on the motor and what isn't Jeff? If your cam is installed you must already have the marks lined up right? Have you rotated the motor since the cam install?
    Every book I've used for reference shows the timing marks as follows. Crank gear, timing mark at 12 o'clock. Cam gear , timing mark at 6 o'clock. This is TDC on #6. If this is how you lined everything up adjust the valves for the #6 position (see previous post) then rotate 1 full revolution and adjust the remaining valves (refer to previous post again /forums/images/icons/smile.gif.

    At this point all the valves will be set and the motor will be at #1 TDC. Drop on the intake and the distributor pointing at number one and you're pretty well done. Ballpark the timing and It should fire immediately. /forums/images/icons/cool.gif

    Rene
     
  11. solowookie

    solowookie 1/2 ton status

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    LOL - actually that is exactly how my timing marks are lined up right now... should make this pretty easy then. I had rotated since I put my cam in, but lined them up at 12:00 & 6:00 before I put the cover on.

    thanks!
     
  12. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    How much did you rotate it? If you know for sure than you can just rotate it back to #6 TDC and start adjusting./forums/images/icons/cool.gif

    Rene
     
  13. CaptCrunch

    CaptCrunch 1/2 ton status

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    Well if you haven't figured it out Jeff... there is a million ways to go about this. Many old hot rodders have their ways. The easiest way if you are still confused is follow a Haynes or GM manual. That way you kinda get the full walk through. Rene's method is probably the easiest if you still have the intake off. Then you can battle the next big opinion issue... how much preload to go. Some guys run no preload and adjust with the motor running... other guys will go as tight as 1 or 1 1/4 turns depending on lifter type. I have always gone a half to 3/4 turn and never really had any problems. I personally don't like adjusting with the motor running. Too dang messy running 12 to 1, a HV oil pump, oiling system mods, and a higher idle. The main key is that you don't have slack in the valvetrain.
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I find 1/2 turn past zero lash works well on my stock valvtrain. I also do not like the adjust while it's running method due to the mess.

    Rene
     
  15. solowookie

    solowookie 1/2 ton status

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    yea I've done that while running method /forums/images/icons/tongue.gif, and I don't want to go there again... LOL definitely too messy! anyway I'll get this adjusted this morning, and then throw the intake on.
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I did explain to him that if the timing marks line up and both valves are closed on the #1 cyl., it's TDC compression for #1, but he didn't post that.

    I agree, 1/2 turn works great. I did mine on the stand and I haven't touched it since. While running is inaccurate and a mess.

    I used the exhaust opening/intake closing method or whatever you want to call it. That's how the instructions said to do it on the cam card, so that's how I did it. The "TDC" method that you mentioned will also work just fine.

    I'll never understand why anyone would do it with the engine running. I'm an idiot and I did it with it off!!
     
  17. DesertDueler

    DesertDueler 1/2 ton status

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    I adjust me while its running. Its the alot easier that way at the track, turn it till it quits making noise, then turn a 1/4 turn. 1/2 for a street car. It takes me about 10 minutes to do it this way, and yes it is acurate it you know what your doing and car listen well.
     
  18. solowookie

    solowookie 1/2 ton status

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    yea you did Tim, but at that point I didn't understand real well how it all tied together - when Rene mention I was already at 6 TDC with the sprockets at 6:00 & 12:00 so some reason a light went on... I was understanding the strokes, how to find #1 TDC etc.

    anyway I follow the method here Rene posted, and it was a total cake walk. I appreciate everybodies help & input here.
     
  19. DesertDueler

    DesertDueler 1/2 ton status

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    BTW, they do make clips that go on top of the rocker arms to deflect oil so it isnt nearly as messy.
     
  20. solowookie

    solowookie 1/2 ton status

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    yea the only thing that bugged me about it was the oil mess, but it did seem really easy & accurate. that's the way I ended up adjusting my engine in JMT when I did it, but when it's apart this far it's pretty easy to use the method I did to adjust it.
     

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