Do I need to spot face these screw in stud bosses for guide plates? PIC

Discussion in 'Engine Topic' started by BondoSpecial, Sep 27, 2011.

  1. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Sep 20, 2004
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    I have a pair of new, odd ball EQ Lightning Vortec heads. They came with screw in studs but no guide plates (or any product literature). I know on some heads that used screw in studs but no guide plates, if you want to add guide plates you need to machine the stud bosses down by the thickness of the guide plate (0.3" I think).

    How can I tell if these heads are already machined for guide plates or whether I need to machine the bosses? Is there a reference dimension I can check?

    Here is a pic of my actual heads

    [​IMG]

    [​IMG]

    Would it really even matter since I have an adjustable valve train whether I was off by 0.3" in stud boss height? As long as the valve cover fits and I can thread the rocker nuts down far enough to obtain the proper lifter preload, does it really even matter? Thanks

    Steve
     
  2. Air_Adam

    Air_Adam Veteran Member

    Usually, the machining is the same with or w/o guideplates IIRC, because if you don't use guideplates under the studs, usually a washer is used. I know this is true for aluminum heads anyway - iron is likely the same?

    That said, those pushrod holes look awfully small for a guideplate setup.
     
  3. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    They are definitely not slotted so they are going to require either self aligning rockers, or guideplates. Guideplates won't affect the sweep of the pushrod vs self aligning rockers. I can certainly take some carbides and open up those holes before I get started, I see what you mean, they are small. As long as I can put the guide plates I already bought on these heads without more machine work I am happy. Thanks for the reply. I think I was thinking about needing to spot face and trim down bosses when converting push in stud heads to screw in...oops.
     
  4. John Wright

    John Wright Veteran Member Lifetime Gold Member

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    Are you sure that the guide plates are .3" thick? Just strikes me as awfully thick for some reason...I'm thinking more like an (1/8") .125" vs nearly 5/16" thick(.3")
     
  5. middleagecrisis

    middleagecrisis Veteran Member

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    I had the same question of my machinist. I am adding guide plates to a set of the '88 Corvette aluminum heads, as I'm going to be running adjustable (non self-aligning) rockers. These heads already have screw in studs, but not guideplates. I was told they did not need to be remachined, just unscrew the studs and install the guideplates.
     
  6. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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  7. John Wright

    John Wright Veteran Member Lifetime Gold Member

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    LOL...OK, that sounds better....now keep in mind that they may be for .3125" pushrods. So maybe that is part of what was stuck in your mind....LOL. You're too young for this CRS stuff that plagues us old guys...LOL
     
  8. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    Those would have been the thickest guide plates ever, eh? Oops. You are giving me too much credit in re: CRS. I think this was a case of DNS. Don't know s....
     
  9. 79RedZ

    79RedZ Veteran Member

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    Hamilton,MI
    I don't have the same heads as you but I ran into the same issue with my patriot vortecs. Those stud bosses look a lot like how mine looked. When we mocked it up the roller tip was to far over toward the outside tip of the valve stem. We ended up having to spot face the stud bosses. All good after that was done. Just curios, how tall are the intake runners on those heads?
     
  10. BondoSpecial

    BondoSpecial Veteran Member Lifetime Gold Member

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    I can measure later, I'm not sure. These are a 170cc vortec type intake runner so they are kind of an upgraded 906 type head from what I have read. Thanks very much for your feedback, that is interesting to know. How much did you take off the bosses? If that winds up being the case I could just use some stamped self-aligning rockers with no guide plates, but I am going to be running .490/.510" lift so I didn't know if that was getting a little aggressive for a self aligning rocker.
     

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