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  1. #1
    Join Date
    Aug 2004
    Location
    Massachusetts
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    13,142

    Default Upper Ball Joint bolts

    What size bolts have you used when replacing the upper ball joints? Reason I ask is that most uppers come with smallish 1/4 screws which fit with some play in the holes of the control arms where the rivets were knocked out. Another kit comes with 5/16" bolts which are just a bit big to fit in the holes and the directions say not to enlarge the holes? I have used the smaller 1/4" before but they make me nervous as I figure the ball joint could shift. I also am considering using the threaded rivet head style screws but the dopes that sell them do not know the size???? All they say is they are OEM. Real good customer service. You would think they could invest in a caliper.
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  2. #2
    Join Date
    Feb 2002
    Location
    LI,NY
    Posts
    19,975

    Default Re: Upper Ball Joint bolts

    The tensile strength of a 1/4" fine thread grade 5 bolt is over 4000 lbs. Even the shear strrenth will exceed the loads the bolts will be under. Dont worry, use the 1/4 bolts
    Jason Cook
    BPG #1675
    "Expert in obsolete technology"

    1968 Riviera GS- some assembly required
    1969 Riviera GS- my first car
    1969 GS-350
    1970 Stage 1 4 speed Aquamist
    1970 GS-455 Bamboo Cream beater
    1971 GS 455 11.93@113.36
    1972 GS-350
    1970 Stellar Industries vintage go kart

    Deo duce, ferro comitante

  3. #3
    Join Date
    Aug 2004
    Location
    Massachusetts
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    13,142

    Default Re: Upper Ball Joint bolts

    Jason, Thanks. I did have the 1/4 in my car I changed several years ago but got confused when I saw the 5/16.
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  4. #4
    Join Date
    Feb 2002
    Location
    austin,tx
    Posts
    3,080

    Default Re: Upper Ball Joint bolts

    The replacement ball joints typically come with Grade 8 bolts also....so you've got more strength there.
    Patton Glade Austin, TX

  5. #5
    Join Date
    Aug 2004
    Location
    Massachusetts
    Posts
    13,142

    Default Re: Upper Ball Joint bolts

    Believe it or not I got two different ones from AC Delco. Both had same part number. One came with grade 8 5/16" and the smaller ones in the other box were 1/4" but grade 5(three slashes). I do not think there is much stress on these but I worry about movement due to the holes in the control arm being bigger than the 1/4" screws.
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  6. #6
    Join Date
    Feb 2006
    Location
    New Hampshire
    Posts
    3,909

    Default Re: Upper Ball Joint bolts

    I always use a 5/16 grade 8 and throw those little ones out. I have seen numerous cars with the smaller bolts have the ball joint floating around in the upper control arm, a recipe for disaster. The holes end up elongated and the bolts get wear marks in them. I tried using the 1/4's before and with the bolts in but not tight, you can move the ball joint around...seems to me it would be difficult to get the ball joint in the exact correct location with them.
    No, its not a chevy motor

    Steve Mario

    '71 Skylark, street/strip beater w/JW and T/A goodies!

    (JW prepped 462 short block, ported T/A Stage 1 TE heads w/stage 3 valves, 1050 Dominator, Super Scavengers, 3400 stall TH400, runs like a raped ape, and leaves brown skid marks on the passenger seat.)

  7. #7
    Join Date
    Aug 2004
    Location
    Massachusetts
    Posts
    13,142

    Default Re: Upper Ball Joint bolts

    Steve, that is what I thought but I spoke with Delco Engineer today and he told me design of ball joint allows use of small screws and placement of screws keeps unit from moving.. My older control arms with small screws were used for several years and never moved. I juts forgt about them being small after not having a problem. Now after starting to build a new set the doubt has just risen back to the surface.
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  8. #8
    Join Date
    Aug 2004
    Location
    Massachusetts
    Posts
    13,142

    Default Re: Upper Ball Joint bolts

    I would also not want to drill out the ball joints smaller holes to accept the larger screws. Any warranty would go right out the window in case of an accident. The other unit with the big screws was designed for them to fit. Moog units come with small as well and bigs would not fit.
    Dave, Seeing Yellow
    71 GS Stage-1 Now Sold.

    Now have real 70 GSX 4 Speed QQ

  9. #9

    Default Re: Upper Ball Joint bolts

    I know this is old but I just had the similar problem. The AC delco upper ball joints (part number 88911380) I purchased only had 5/16 grade 8 bolts and the size of holes in the ball joints were 5/16" but the holes in my control arms are only 1/4"
    Is it bad to drill the control arms?

  10. #10
    Join Date
    Mar 2008
    Location
    Mi
    Posts
    3,065

    Default Re: Upper Ball Joint bolts

    Dave,
    this is what I used. (threaded rivet head style screws"

    Nelson
    Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out and loudly proclaiming: "WOW! WHAT A RIDE!!"

  11. #11
    Join Date
    Jan 2011
    Location
    Westhampton, MA, USA
    Posts
    1,180

    Cool Re: Upper Ball Joint bolts

    Quote Originally Posted by Carcrazy View Post
    I know this is old but I just had the similar problem. The AC delco upper ball joints (part number 88911380) I purchased only had 5/16 grade 8 bolts and the size of holes in the ball joints were 5/16" but the holes in my control arms are only 1/4"
    Is it bad to drill the control arms?
    It's not going to hurt anything to drill the control arm out to 5/16th... It's not a big size jump... I would say stay with the grade 8 bolts as well... Don't use lock washers... Get regular washers and grade 8 lock nuts... I've seen way to many lock washers rot out or break and than you have a sloppy fit...

    I never use lock washers, I only use washers on both sides and lock nuts...

    He was only worried (by the sounds of it) about the warranty if for some reason he needed to send the control arms back for warranty...
    "Courage is being scared to death but saddling up anyway" John Wayne

    BCA # 45934 / Central New England Chapter, BCA / BPG #2313
    Buick GS Club of America # 2943 / Northeast GS/GN Club

    Now: 1970 Buick GSX Tribute Car, Stage 2 455, SP TB 400, 3.42 Positraction
    Before:
    1968 Buick GS California, Midnight Blue, 350 ST300, than a 1974 455 TB400
    1971 Buick GS, Lime Mist Green, 350 TB350
    1974 Buick Century Wagon, Dark Brown, 455 TB400
    2000 Buick Regal

 

 

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