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Thread: Rocker sweep

  1. #1
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    Default Rocker sweep

    So i finally pulled my finger out and started reassembling this cleveland.
    Ended up splurging on a set of yella terra platinum rockers for it too.
    The dilemma now is no matter what i do bringing the rockers up or down, i can only get the sweep on the valve tip to be at best around 100thou.

    The thing has 633 lift and chi heads.
    Stands that came with the rockers are 22mm. Tried 19mm stands. 200thou on spacers on both stands in thou increments and froze myself in the garage in the process.

    Any ideas would be greatly appreciated before my head explodes and frostbite gets me too.

  2. #2
    427
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    Im no expert, but i would have thought 100 thou is enough. Is the pushrod length correct. As long as the sweep is in reasonably close to the middle of the valve head, thats what i shoot for...

  3. #3
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    The trick is setting your rocker to mid lift. So yours would be 0.316in. That's means when your valve is closed and you measure the centre of the roller tip down to the centre of the rocker trunnion, it should be 0.316 in. That way you get even rocker movement on the valve from closed to mid to open. It is the most efficient way to operate your rocker. Any sweep that occurs will be at its smallest.

    These measurements are following the angle of the valve stem. not the rocker stud.
    Last edited by Castiron355; 10-07-2018 at 02:04 PM.

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    427, these rockers are shaft mounted.. The stands determine the height but i tried everything,,, heights,, ran the rocker by hand with a dial guage. Went to trying it with different pushrods and hand turning it over in desperation incase i was somehow interfering with the movement etc.
    Castiron355, mid lift has been my way and when focusing on the roller tip on valve always looked ok but that damn sweep was everywhere every time blued it up. So warm day, no distractions, wife and kid out and went at it again. I'd been so focused on the rocker and everything it was doing that I didn't notice the damn cut down checking springs turning the valve through the range!!
    Last edited by torana74; 17-07-2018 at 11:03 PM.

  5. #5
    427
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    Sounds like you are on to something! Hope it works out well !

  6. #6
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    Sounds like you have nailed the problem.

    I'm not a fan of using "checking springs" for any steps in assembly, preferring to use the intended springs, for more accuracy.

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    Depending on your choice of pushrod, it's also worth checking to see that the pushrod isn't contacting the underside of the rocker arm towards or at full valve lift.

    My previous engine, Holden 308, early iron head, has the early YT 7/16" bolt-on's (early YT Dash-3 rockers) before they started using the Platinum branding, and with Crow 3/8" Chrome Moly 080" pushrods, I found that nearing full valve lift (.710") the area of the pushrod just before it transitions to the smaller 5/16" end has getting hung up on the rocker arm body and had to be clearenced with a die grinder. The contact with the arm and pushrod was causing the pushrod to be pushed slightly out of the cup in the arm, and was providing additional valve lift.

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    Looks like you’ve solved it. Nice one!

  9. #9
    427
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    And you're obviously not in Melbourne coz you mentioned something about a warm day!

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