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Thread: Rocker Arm help

  1. #1
    Im looking to go to a set of roller rockers. I am now running stock stamped steel non adjustable rocker arms and have no experience on how roller rockers are set up. I have a couple of questions on setting up to achieve correct geometry. From reading a couple of articles on the web this is how I see it. Tell me if this is right.
    For stud mounted roller rockers, they use guide plates which hold them inline with the pushrod and valve tip and prevent them from rotating off the valve right?
    The nut is used to adjust the height of the rocker on the stud which gives you correct geometry in relation to the valve tip and requires an adjustable pushrod to figure out the correct length pushrod needed?
    Is this correct so far?

  2. #2
    Blown 472
    Yes, the guide plates keep them lined up, the nut lets you set the lash, and the adjustable push rod is for checking the geo and then getting push rods made to that length, if you are just switching over put one on and set the lash and check it, you might be right on the money allready.

  3. #3
    Senior Member
    Join Date
    Mar 2010
    Yes, as long as you are running a BBC/BBF it is a pretty easy deal. If it is a SBC you need a self aligning rocker so that the heads do not have to be machined for guideplates.

  4. #4
    Ok, next question. The rockers that have the adjustable tips such as shaft mounted rockers, how do you adjust for the correct geometry on these. It looks to me like they bolt down to the head and have no stud or guide plates. The adjustable tip is used to set lash, but the height is not adjustable, so how do you adjust for geometry?
    Trying to figure this out so bear with me.

  5. #5
    Blown 472
    You do it with the push rod, just like on the mopars, they are shaft mounted so you have to get the correct push rod.

  6. #6
    Can you elaborate on that a little.
    So I install the rockers and the roller tip is sitting on the valve tip and set 0 lash (hydralic lifter), if the geometry is wrong, how do you go to a longer pushrod if the rockers are bolted down to the head and not adjustable for height like stud mounted rockers?

  7. #7
    But how do you change the pushrod length on shaft mounted rockers if they are not adjustable for height like stud mounted rockers are. Thats what I don't understand. Thanks.

  8. #8
    pushrod length alone does not fix bad rocker geometry, the comination of valve length, rocker height and pushrod length all control it. on "bolt down style" rocker arms (individual or common shaft) you either shim the stands or machine the pedestals to move the rockers up/down. The pushrod ( or pushrod side of rocker arm adjuster) is only to set valve lash. With common shaft rocker arms (in your picture) it is very important that the valve tip height on the intake and exhaust valves is the same. (lay a straight edge across tips of all valves) so you arent trying to tilt each pair of rockers. Also if the cam base circle is different intake/exhaust the pushrods may need to be different lengths.
    hope that helps, Pat

  9. #9
    Thats what I was looking for. Thanks for the answer.

  10. #10
    Blown 472
    In general terms it is adjusted by using shims under the rocker shafts (best suited to mechanical cams). It is also a function of push rod length.
    First of all you determine the push rod length you need by setting up the rocker adjusters so that only 1 or 2 threads are showing below the rocker. Then you mark the top of the valve with machinist blue or a marker and then you rotate the crank through a couple of revolutions. check the pattern. It should be very narrow and in the middle. If it is not, you shim the shafts up, .015" at a time until you optimize the pattern.
    If the shafts need to be lower, it is more difficult to correct (machining required).
    Had to double check on this, got it from moparts.

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