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Valve adusting question???

Discussion in 'The Hokey Ass Message Board' started by BinderRod, Aug 14, 2010.

  1. BinderRod
    Joined: Jul 9, 2006
    Posts: 1,736

    BinderRod
    Member

    I adjusted the rockers on my SBC. A buddy tells me to set zero lash then tighten 1 full turn more. Now it feels and sounds like I am running on 7 cylinders. He swears he is right. I thought fine. Checked timing and it still sounds like crap. It felt like a fouled plug so I changed them. Still sounds like crap. I changed plug wires because one of them got into the headers a while back. Still sounds like crap. I changed cap and rotor. Still sounds like crap. Put fuel dryer in the tank thinking I might have water in the tank. Still sounds like crap. I am going the go out tonight and re run the rockers and pre load them with a 1/2 turn past zero lash. Any more ideas?
    The old truck gets sideway hitting 2nd gear and runs like a stripped ass ape but just dosen't feel or sound crisp. In ase anyone wants to know what I am working with here it is.

    The block is a ZZ4 9.6 to 1 copmpression with Dart Pro 1 heads, ZZ430 Hot Cam kit, 1:6 roller rockers, air gap intake and 750 Holley DP. It has a 700R4 and 3.73 10 bolt posi.
     
  2. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,906

    need louvers ?
    Member

    I'd say that you are probably too tight and the valves are staying open. A half turn is a bit more in line with normality when your using aftermarket stuff, and I frequently use a 1/4.
     
  3. shortbed65
    Joined: Feb 20, 2009
    Posts: 204

    shortbed65
    Member
    from ne Ill

    I set sbc lash while running with 1/8 turn increments (use those deflectors - Less clean up)
     
  4. Road Oiler
    Joined: May 31, 2010
    Posts: 146

    Road Oiler
    Member

    What happens if the amount of Hydraulic Lifter Preload is wrong?
    If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter's retaining lock, and this could cause the lock to fail. If the opposite occurs and the pushrod descends too far (more than .060"), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it.
    Therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and the lift to be higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause "backfiring" from the engine.



    Information from Crane Cams site.
     

  5. I go with a 1/4 turn on all, let it settle out and go another 1/4 turn all around for a total of a 1/2. One full turn is too much, do them over and you should be ok.

    Bob
     
  6. Retrorod
    Joined: Jan 25, 2006
    Posts: 2,029

    Retrorod
    Member

    When I ran a large GM service department for many years, we had the best overall success setting them at 3/4 turn. Most of the guys would set them at 1/2 turn while running and then after it was shut down, give them an additional 1/4 turn. We NEVER had a come-back using that method.

    A full turn is right on the edge of bottoming out the lifter, just a little varience in anything and you create a miss.
     
  7. poboyross
    Joined: Apr 29, 2009
    Posts: 2,142

    poboyross
    Member
    from West TN

    I used the EO-IC method, and then did 1/2 turn...no problems so far and runs purdy good for a tired ol' 283.
     
  8. All of the GM manuals that I have call for 3/4 turn.
     
  9. fab32
    Joined: May 14, 2002
    Posts: 13,985

    fab32
    Member Emeritus

    I've never gone past 1/4 turn from zero lash. That way you get the maximum RPM out of the combination. Be sure your fully up to operating temperature and the the temp is stabilized (oil viscosity is at running value when you do this). Back each lifter off (one at a time) until audible click is heard, slowly retighten until click goes away, then slowly add 1/4 turn. This method does require a readjustment about once a year (sometimes sooner) as normal wear will create some lash increase but in the meantime your getting full benefit of the cam specs.

    Frank
     
  10. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,364

    dave lewis
    Member

    Thats how I have been doing it for 40+ years !
    Slightly messy, but works the best..
    The few times that I did it "by the book" (3/4 or 1 turn ) , I had to go back and do it over to 1/4 turn.
    Dave
     
  11. Hebert Racing
    Joined: Aug 1, 2010
    Posts: 27

    Hebert Racing
    Member
    from Louisiana

    I've always adjusted them 1/4 to 1/2 turn past zero lash , never saw any reason to go any tighter.
     
  12. I've always set hydraulics cold ... 1/2 turn ... reinstall valve/rocker cover ... I use silicone on both sides of the gasket to ensure no leaks ... rocker covers only need to come off again if I am changing intakes. Only ever had one issue with valve adjustment and that was because the press-in studs were coming out (SBC). This is what works for me.
     
    Last edited: Aug 15, 2010
  13. BinderRod
    Joined: Jul 9, 2006
    Posts: 1,736

    BinderRod
    Member

    Thanks for all the help. I ran the valves again today at 1/2 turn. The miss is gone and all is good. Thanks Keith
     
  14. poboyross
    Joined: Apr 29, 2009
    Posts: 2,142

    poboyross
    Member
    from West TN

    BOOYAH! Glad to hear it was an easy fix :)
     
  15. budd
    Joined: Oct 31, 2006
    Posts: 3,478

    budd
    Member

    i have always done one full turn on stock lifters, this is what i was told would place the plunger in the center of its travel, i checked this once and yes i could get two turns before bottoming out the plunger, but 1/4 turn was often called for with aftermarket lifters. sticky lifters can make this job tough.
     

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