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Hot Rods Pontiac rocker arm nuts

Discussion in 'The Hokey Ass Message Board' started by Chewie46, Apr 11, 2015.

  1. Chewie46
    Joined: Oct 10, 2002
    Posts: 47


    My 32 roadster has a 59 389 Pontiac in it. The rocker arm studs are 5/16. The rocker arm nuts on my motor are warn out and keep backing off. I can't find new ones anywhere.Any suggestions?
  2. DDDenny
    Joined: Feb 6, 2015
    Posts: 16,059

    from oregon

    Deuces likes this.
  3. DDDenny
    Joined: Feb 6, 2015
    Posts: 16,059

    from oregon

    Forgot to mention:
    Be advised; there are some locknuts on the market that have been known to remove threads when being removed, IIRC, they are the ones with the little slits thru the first few threads.
    Look up "crimp" or "distortion" locknuts.
  4. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    Are they backing off? Or are your studs puling out?
    Elcohaulic and Deuces like this.

  5. oldtom69
    Joined: Dec 6, 2009
    Posts: 576

    from grandin nd

    just checking-you do realize they are NOT adjustable like a chevy,they get torqued down and are bottomed out.I'm guessing the threads on the studs are pretty worn too_Out of desperation I have had luck crushing the rocker arm nut slightly in the vise
    lippy and Deuces like this.
  6. draggin'GTO
    Joined: Jul 7, 2003
    Posts: 1,774


    This is correct, the Pontiac valvetrain is non-adjustable from the factory with very few exceptions, those exceptions would be very rare performance engines like the 400 RAII & RAIV as well as 421 Super-Duty engines. The factory rocker nuts on common Pontiac V8s are not made to lock onto the threads of the stud.

    However if you make changes that render useless the factory tolerances that allow the nut to simply be torqued onto the tapered shoulder of the rocker stud (head milling, aftermarket cam, valve job, etc.) then you need to make it adjustable.

    You can buy small-block Chevy self-locking adjusting nuts and then adjust the valves just like you would on a Chevy. The rocker nuts should be 3/8-24 thread, not 5/16. If they are 5/16 you should be able to find a self-locking nut in that size.
    Last edited: Apr 11, 2015
  7. saltflats
    Joined: Aug 14, 2007
    Posts: 11,248

    from Missouri

    I was thinking that pontiac had 3/8 studs that step down to 5/16 for the nut and the nuts have a step inside them that would lock down on the 3/8 part of the stud.
  8. draggin'GTO
    Joined: Jul 7, 2003
    Posts: 1,774


    I do know that later heads with press-in studs are 7/16" diameter on the bottom and the upper portion tapers to a 3/8-24 thread. Even the '67 and up screw-in stud heads have the same sizes with 7/16-14 threads into the head and 3/8-24 threads at the top.

    The nuts have a taper on the bottom that matches up with the taper on the stud, right at the transition from the 3/8 thread to the 7/16 shank of the stud.

    Earlier Pontiac heads may have used a smaller stud size, not quite sure since I haven't had anything older than 1964 in my possession.
  9. Hotrodjohn71
    Joined: Feb 25, 2018
    Posts: 74


    Can I revive this old thread by asking a few questions?

    1 have a 1965 Pontiac 326, rebuilt, and bone stock and with stock equivalent hydraulic flat tappet cam from a Mahle master rebuild kit that a local machine shop provided with all of the machine work.

    I have all my rocker stud nuts torqued to about 25# (this is a non adjustable valve train as referred to previously in this thread), but still have about 3 or 4 rockers that tick.

    I would like to dial the valves in with the Poly Locks, but I have read that they are prone to come loose on stock studs and that certain ARP studs are better but I believe my studs are press-in and I'd really rather not tap them all out at this time. Are Poly Locks reliable on stock studs?

    Finally, This sounds outlandish, but what would be thought regarding getting 16 washers (spacer shims) of let's say .100" thickness and putting one under each of the 16 rocker nuts.

    Then running the engine (already warmed up) and dialing in the valves just like you would with the Poly Locks (turning about 1/4 turn after ticking stops) then simply running a lock nut down on each of the 16 rocker nuts?
  10. lostone
    Joined: Oct 13, 2013
    Posts: 1,998

    from kansas

    On all my pontiac motors I ran Mr. Gasket poly locks and they worked perfectly. Had some of my motors over 100,000 miles put on them with no problems.

    One trick to using poly locks is the stud top. You want it flat. So one an engine that had the heads installed, I'd remove the valve covers, pull the rockers and push rods. Take a piece of news paper and push down over the studs and a piece of tape around the stud to the news paper then take my 4-1/2 grinder with a flap wheel and just touch the top of the studs to flatten them. Air blower to blow them off then carefully pull the news paper and tape and reinstall the rockers and push rods and adjust. No problem!

    If the motor has the intake off ( this is how I do all my motors) I use a small paper clip and just adjust the polys until I can just slid the paper clip between the lifter plunger and the lifter plunger retainer clip, now that is with the poly tightened down. Never had to readjust the valves once I got it running doing it this way. Gives about .015 preload and pontiac motors love that.
    Mark Grabo likes this.
  11. '51 Norm
    Joined: Dec 6, 2010
    Posts: 760

    '51 Norm
    from colorado

    I had a 421 with a solid lifter cam and that is how the people who built the engine made the valve train adjustable.
    I did have to adjust the valves regularly but I thought that was just part and parcel of running a solid cam.
    Deuces likes this.
  12. Deuces
    Joined: Nov 3, 2009
    Posts: 21,947

    from Michigan

    The best way to grind the tops of the studs is with surface grinder... With the studs mounted in a jig... That's the way I would do it...
  13. flamedabone
    Joined: Aug 3, 2001
    Posts: 5,033


    The best way is to replace the original studs with non-bottle neck screw in studs and poly locks. If your heads already have screw in studs, it is no big deal, but if they are press in, the heads have to come off.

    Deuces likes this.
  14. Almostdone
    Joined: Dec 19, 2019
    Posts: 701


    I recently installed poly locks on a Chevy 348. I was stupid and filed the studs flat with a hand file and trial and error - it came out fine. Engine was assembled and in the car. However, if I had run a nut down flush with the top of the stud and filed it flush with the nut it would have been much quicker.

    Deuces likes this.
  15. Just buy a set of Mr. G poly locks.. Never mind the clickedy clack stuff.. Just run the nut down by hand down while spinning the push rod in your fingers.When you get to zero lash, run the nut down another half a turn. Lock the set screw hard as you can with a short allen wrench. That poly lock isn't going anywhere..especially with a stock cam and springs,..and neither is the pressed in stud.. Not a race engine . Probably a good idea to not listen to the pseudo racers on this one ;-)
    egads likes this.
  16. I run the poly lock nuts on a 68 400 (stock GTO engine) and actually adjusted them hot running like Chevy style. Locked down and haven't moved for years.
    The poly locks slide over the bigger diameter so you can make a pseudo adjustable setup.
    Deuces and fordflambe like this.
  17. fordflambe
    Joined: Apr 9, 2007
    Posts: 558


    I just converted a set of 64' rocker studs (oil passage thru stud) to a set of these solid studs. Used comp cams roller tip stainless rockers with poly-locks and works just fine. Studs in my 64' heads were screw-in so this was an easy swap. I dont know about 59' heads, they may be pressed in studs?? When using this conversion, you have to replace the solid push rods to hollow push rods for oiling...........|ampid:pL_CLK|clp:2334524
  18. lippy
    Joined: Sep 27, 2006
    Posts: 6,092

    from Ks

    Here's a variation of Oldtom69's crush it in the vise scenario. Lay the nut on it's side on a flat, on the concrete floor and smack it with a hammer. Put it on see how it fits. :D
  19. Interesting ..How do you go about setting up the engine when new?
    Hotrodjohn71 likes this.
  20. the SCROUNGER
    Joined: Nov 17, 2005
    Posts: 514

    from USA

    original hydraulic cammed Pontiac V8's had non-adjustable valves, the rocker nut gets torqued to 20 ft. lbs.
    the studs were 3/8" on top, and 7/16" on bottom, and were either threaded in, or pressed in.
    the stud was called a bottleneck stud, and the jamb nut would bottom on that bottleneck ledge, where the 7/16 and 3/8 threaded section met in the middle of stud.
    early SD421 had full length 7/16" studs pinned into the head, fully adjustable.
    1967-up heads were redesigned and were screw in studs, albeit with the original 7/16" base, and 3/8" top, and bottleneck just like the earlier pressed studs.
    Ram Air IV and V 400 engines had full length 7/16" studs, fully adjustable, just like a big block Chevy.

    ok, assuming you have the bottleneck design with the 3/8" studs threaded on top, pressed or screwed into the heads- and you want to convert from non-adjustable to adjustable, you have 2 options using the original studs:

    1. buy 3/8" poly locks, they're quite cheap, and use them- remove the original jamb nut

    2. go to your local hardware store, and just buy 16 locknuts, 3/8 fine thread. look for hardened, or grade 5, grade 8. or, buy them for another engine to spec such as a Chevy, Mopar, Ford, etc. and use them- then you're getting bona fide rocker arm nuts or proper metallurgy. just remove the jamb nut, and replace with he locking nut- which is effect, a nut with an oval imperfect hole, so it grabs the threads and doesn't back off.

    the problem with lock nuts of that type is, they shave some metal from the threads on the studs every time they are r/r or adjusted, after many adjustments eventually strip the stud. just ask any smallblock Chevy guy, those were notorious for backing off and being stripped. I'd take valve covers off a Chevy with a miss, the rocker and nut would be off the stud, laying on the head.

    furthermore, keep in mind the 3/8" stud is not as strong, if you run a mongo cam, or float the valves, it can and will snap the stud off at the bottleneck. I've witnessed a '64 GTO snap off a screw-in stud 7/16" stud at the drag strip, on a 455 w/casting 16 heads, RA IV cam and 1.65 rockers, he floated the valves, did not have the lifters set to zero lash, pumped the lifter up and broke a stud off. fortunately I had a spare bottleneck stud w/nut in my toolbox, we simply unthreaded the snapped off stud from head, installed the bottleneck w/jamb nut torqued down, he finished the day with it.

    I ran the stock bottleneck studs in a 400, RA IV cam, #12 heads engine, floated valves twice street racing. that engine would pull to 6200, then stop pulling, but would rev to 7200 then float the valves, bend pushrods, and snap the studs and break rocker arms. point being, valve float will break even a 7/16" stud on a Pontiac. I'd carry spare pushrods, studs, rockers in a toolbox in the trunk.

    the best strongest setup for Pontiac is, replace with big block Chevy 7/16 studs, polylocks. presto she's fixed for good- providing you have a solid cam, and don't pump up lifters on a hydro cam.
    Last edited: Oct 16, 2021
    Deuces, Hotrodjohn71 and '51 Norm like this.

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