Question on getting correct pushrod length

Discussion in 'High Performance Modifications' started by henry1088, Jun 7, 2009.

  1. henry1088

    henry1088 Veteran Member

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    I got a set of adjustable pushrods, some checking springs and the little proform dohickey to check for proper length.

    First thing is that I think I wasted money on the proform tool. I put that on the stud and according to the instructions the stock pushrod is too short. However, with the checking spring installed and some marking compound on the stem it is clear that stock is too long.

    So I used my adjustable pushrods and with .150 shorter than stock the pattern appears to mimic this http://www.compcams.com/information/Products/Pushrods/ .

    I'm hoping I'm doing this right. Has anyone else had to get shorter pushrods by this amount? What could affect this? The best I can tell is that my installed height is 1.800. The heads are pro topline, the rockers are crane energizer and the cam is a lunati street master.
     
  2. night rider

    night rider Veteran Member

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    I never use light checking springs check pushrod lenght or valve to piston clearance.. Any time I have tired I got bad results.

    Use the valve springs you will be running on the engine.. Set your adjustable pushrod to std lenght for sbc.

    Mark the top of valve stem with paint, machinest blue, or a marker... Install rocker you will be using, adjust the valve, turn engine over by hand with a breaker bar 2 full rounds.

    Tak rocker off.. Look to see where the line/mark is on the valve stem... Your wanting it in the dead center of valve.

    If it's offset towards exhaust side of head, pushrod is too long.. If offset towards intake pushrod is too short.

    Take adjustable out, reset it to next lenght, and re do the above.

    Keep going at it till you get the witness mark in center, them measure your pushrod and rder a set that lenght.

    Most engines with aftermarket heads will need longer than stock, not shorter
     
  3. 1972L

    1972L Veteran Member

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    I find it interesting that very few people take into account hydraulic lifter preload, or solid lifter lash when doing this.
     
  4. henry1088

    henry1088 Veteran Member

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    And then again some people do. Considering that a rocker stud is 24tpi that means one turn is about .041". If I preload using half a turn that would be around .021". So if I use checking springs that don't apply enough pressure to collapse the lifter I need to add .021 to my measurement.
     

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