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Spinnin' rocker studs/Pontiac

Discussion in 'The Hokey Ass Message Board' started by gearjam1, Oct 2, 2007.

  1. draggin'GTO
    Joined: Jul 7, 2003
    Posts: 1,792

    draggin'GTO
    Member

    Most every Pontiac V8 (other than a very few rare 389/421 Super Duty engines with solid lifter cams) has a hydraulic cam and lifters, the lifter pre-load is set by simply torquing the factory rocker nuts down onto the tapered portion of the rocker stud.

    (The '68 Ram Air II and '69 -'70 Ram Air IV 400 engines have a hydraulic cam and a factory adjustable valvetrain, two very rare engines that are also an exception.)

    When these engines came out of the factory originally, the tolerances were held in such a way that the valvetrain could be built this way, no adjustment needed.

    But once you mill the heads, the pushrods would need to be shorter to use the 20# torque. If you grind the valves but don't mill the head, the valves stem tips end up higher, necessitating a longer pushrod to keep the factory 20# torque. And so on, once you start machining on the bolck or heads or change the cam, in many cases you won't be able to use the factory setting anymore.

    The 20# torque setting is just to make the nut stay tight on the tapered portion of the rocker stud, nothing more.

    Best to make life easy and make the valvetrain adjustable so there's no question you have things right. A lot of Pontiac builders make the mistake of torquing things down to 20# and end up with a trashed set of heads, bent pushrods, bad cam, etc.:(

    The rocker balls should not hang up on the studs, intake and exhaust rockers and rocker balls are the same.
     
  2. gearjam1
    Joined: Sep 6, 2006
    Posts: 248

    gearjam1
    Member

    -That info helps me a lot. My "guess" would be that the machine shop installed oversized studs on the one's that were loose, but didn't install balls that matched the oversized studs? Does that make sense? My manual says if the studs are loose, then oversized studs should be used. If the studs have stripped threads, or are broken, then standard sized studs should be used... _OR_ is the "above-head" part of the stud, standard size??

    Sorry 'bout all the questions...but, I'm trying to learn. -Thanks! Tony
     
  3. Zettle Bros.
    Joined: Oct 17, 2004
    Posts: 1,358

    Zettle Bros.
    Member

    We had this same little loosening problem with the studs on the GTO. We finally used the '63 Super Duty stud that had the nut cast to the stud. Problem solved.
     

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