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Technical SBC split stud bosses threading in rocker studs

Discussion in 'The Hokey Ass Message Board' started by turboki, Jun 15, 2020.

  1. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Just wanted to share an annoying experience from this weekend. I picked up a "rebuilt" 350 a few weeks ago and noticed that half the rocker studs were stripped...so I got down to the task of pulling and tapping the heads and throwing in some studs. Now this might have been my mistake, but I didn't get the hex studs, instead I got the hexless screw in studs from Speedway. BIG mistake. I tap everything, start to thread them in. Figure start with low torque just to get them started (20lbs) and boom cracked the first boss. Figured, no way did 20lbs just crack the head...prolly already had a crack in it. Try a second one...same result. The heads are 185s, so nothing to write home about...but still annoying to lose half a Saturday and machined head to something so stupid. Live and learn, and then keep setting money on fire by working on cars.
     
  2. Ericnova72
    Joined: May 1, 2007
    Posts: 401

    Ericnova72
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    Let me get this straight....It took 20 ft lbs just to start them into the threads?? Or you were jamming that little shoulder at the end of the base threads against the casting with 20 ft lbs torque??

    if they were winding in that hard, something is bad with your tap.

    If you were jamming the little shoulder that hard, no wonder it split, the edge of that shoulder is shaped like a splitting wedge. You're not supposed to torque that style stud into the head

    That type of stud should be set just a little more than hand tight, with loctite on the threads.
     
  3. So you came here and your 1st post a gripe?
     
    warhorseracing likes this.
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 46,374

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  5. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,259

    56sedandelivery
    ALLIANCE MEMBER

    My 265 and 283 Powerpack heads, and if I ever get around to assembling the short blocks, both have the shoulderless, screw-in studs; no problems with them. Maybe there's something "wrong" with the Speedway studs?
    I am Butch/56sedandelivery.
     
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  6. treb11
    Joined: Jan 21, 2006
    Posts: 3,521

    treb11
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    Very HAMB traditional
    Sent from my SM-G965U using The H.A.M.B. mobile app
     
  7. Budget36
    Joined: Nov 29, 2014
    Posts: 3,592

    Budget36
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    Butch,

    What was your method to install them? In a few weeks I'm pulling/tapping a set of heads for them. I'd read 25/30 ft/lbs, but this now doesn't seem right?

    Thanks.
     
  8. X-cpe
    Joined: Mar 9, 2018
    Posts: 973

    X-cpe

    Metric threads from overseas? Have you tried threading them into a known good nut of the right diameter and pitch?
     
    Atwater Mike, 1934coupe and 41rodderz like this.
  9. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,522

    seb fontana
    Member
    from ct

    There are some studs that the threads are not full depth for sealing purposes but I've only seen them as oem in 289 Ford K motors and B302 [69-70]. All aftermarket that I have dealt with have normal 7/16-14 threads and screw in easily.
     
  10. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Not a gripe...just a vent. Idk...maybe help someone else not screw up their heads like I just did...

    Also, the studs went in just fine by hand. Its when I was tightening up the bolts on the rocker arms that the bolt kept spinning. There were no torque specs on these, so I figured they would just tighten up as a combo, turns out I was wrong. Just a lesson learned.
     
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  11. Fordors
    Joined: Sep 22, 2016
    Posts: 2,821

    Fordors
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    I’m a bit confused by your latest post. I guess you meant to say the rocker nuts were tight on the new studs and that the studs were spinning and as a result tightening further in the head. Chevy rocker nuts are an interference fit on the stud but should still pose no problem.
    As @Ericnova72 said the small shoulder on the studs is sufficient to bottom against and lock the stud in the head. I’ve done lots of heads in this manner, and even did a set for a guy with a 6-71 blown 350 with the engine still in his 68 ‘vette.
    50 years ago Dorman sold those studs, a lot of auto parts stores had drawers of various Dorman fasteners and hardware. Today those are sold by many but I imagine they all come from the same source, even the ones from Speedway which you mentioned
    you purchased.
    We either need more info on how you installed them or maybe a few pictures will help show where your project went south. How did you pull the old studs and how did you keep the tap aligned?
     
    1934coupe likes this.
  12. mkubacak
    Joined: Jun 20, 2005
    Posts: 154

    mkubacak
    Member

    @turboki

    Please take some photographs of the cracked head, the studs you threaded into it, and the rocker arms so we can get a better idea of what you are working on here. That could really help some people out in the future if they can see what went wrong.

    Thanks.
     
    Atwater Mike likes this.
  13. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Absolutely. Just ran out to the shed and snapped some photos. Here is the crack.
    [​IMG]

    The nut/rocker
    [​IMG]

    Here is another stud that is just finger tight:
    [​IMG]

    This was the tool I used to pull the old ones and as a tap guide:
    [​IMG]
     
    mkubacak likes this.
  14. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

  15. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,722

    1971BB427
    Member
    from Oregon

    I always run the studs with a nut as the shoulder makes them much stronger than the type without a shoulder.
     
  16. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Lesson learned! Luckily I just messed up one head. Now I just have to find a replacement 185 head....or a pair of 487 heads.
     
  17. That head is not necessarily ruined. I would take both heads to my machinist, show him the crack and ask if he could pull the rest of the studs, then machine the heads for screw in studs and guide plates. The stud boss will have machined down the thickness of the guide plate and the thickness of the hex on the proper screw in stud. From your picture, it appears that would be past the crack.


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  18. 1934coupe
    Joined: Feb 22, 2007
    Posts: 4,016

    1934coupe
    Member

    If only people would fill out their profile they may find others could help them out. Truckdoctor hit on a solution to the problem.

    Pat
     
    Truckdoctor Andy likes this.
  19. indyjps
    Joined: Feb 21, 2007
    Posts: 3,881

    indyjps
    Member

    Those heads have had pinned studs at some point. Does the other head have pins on the studs still?
    The studs have likely been replaced once when they got pinned, or if someone went to the trouble to pin them they planned on running some lift and heavy spring.

    Who knows the full history....I'm guessing those have been beat on pretty hard in the past. If the studs were relaced in the past, you may not have done the damge, just opened the crack.
     
  20. Fordors
    Joined: Sep 22, 2016
    Posts: 2,821

    Fordors
    Member

    For the great majority of heads used on the street the studs without the jam nut are are perfectly acceptable. They are cheaper, perform as intended, require no machine work and the job can be done by the DIY method, even on the engine if you so desire.
    If I’m looking at the photos correctly that rocker arm is jammed against the casting with the Posi-Lock type rocker nut.
    The studs only needed to be put in until the shoulder snugged up against the head and as mentioned earlier they could be Loc-Tited, but I’ve done them without thread locker before with no issues. The Posi-Loc nuts aren’t a good choice for those studs either. For the set screw to positively hold the nut tight the studs need a flat ground surface and this type of economy stud is not ground on the end.
     
    Hollywood-East likes this.
  21. Put that same exact set of studs into some Gen II heads, using the exact same tool, all purchased from Speedway with 0 problems.

    I'm thinking the holes for pins didn't help the casting integrity, especially after tapping them
     
    Truckdoctor Andy likes this.
  22. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    It dawned on me that they may have been beaten on before. One of the studs was already a threaded stud and the others were also replaced with the last rebuild. Unfortunately whoever rebuilt them last also stripped cross threaded a few of the nuts, which is why I got to replacing them. I honestly don't think is worth the hassle of getting them machined out and fixed cause I could just get some ATK reman heads for half the price.
     
  23. squirrel
    Joined: Sep 23, 2004
    Posts: 46,374

    squirrel
    Member

    I can imagine why it cracked. I don't know if I can explain it well, though. At the end of the threads on stud, it acts as a taper, and puts a lot of radial load on the casting when you tighten it with the polylock. The casting is not strong there, in tension.

    Thanks for the warning, now we know
     
  24. doyoulikesleds
    Joined: Jul 12, 2014
    Posts: 258

    doyoulikesleds

    how hard did the old studs come out i have done lots of that style stud and only ever seen heads crack trying to remove old studs with lots of rust on the bottom.
     
  25. Ericnova72
    Joined: May 1, 2007
    Posts: 401

    Ericnova72
    Member

    Can I ask why you want to run either of those casting numbers??
    There is nothing great about those heads, just typical '70's smogger's that don't flow all that well nor make great power with a poor open chamber design.
    The 487's are a little better then the 185's which are really small valve....not saying much good though.
     
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  26. indyjps
    Joined: Feb 21, 2007
    Posts: 3,881

    indyjps
    Member

    Im still interested in the holes drilled thru 1 side of the stud boss. These aren't stock. Someone has pinned the studs in the past or had the heads prepped for pinned studs. Did these heads have a steel roll pin thru the casting boss into the stud, before the screw in studs were installed?
     
  27. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Yes they had pins in there. I pulled them all out before removing the studs.
     
  28. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    Im looking for low compression heads (70+cc) on the cheap cause I wanna throw an underdriven supercharger on it. More for fun, rather than crazy HP numbers. I can pick up a set of rebuilt 185s for $500...or I could just splurge and go for some world performance heads for $1200...
     
  29. turboki
    Joined: Jun 15, 2020
    Posts: 15

    turboki
    Member

    No rust on them at all, but it took a 3ft breaker bar to spin the nut and pull them out. My impact gun did nothing. Im thinking that the studs that were put in were slightly oversized. So between them being pressed in, and the hole from the pin on the side combined made the bosses really weak.
     
  30. treb11
    Joined: Jan 21, 2006
    Posts: 3,521

    treb11
    ALLIANCE MEMBER

    Did the threaded studs require reaming or drilling of the hole prior to threading? I would be surprised if they didn't.

    Sent from my SM-G965U using The H.A.M.B. mobile app
     

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