1961 Carb Stud for single 4 barrel carb
I am trying to confirm if GM started installing a shouldered stud in the 1961 model year for single 4 barrel carb models. The drawing of the stud shown in the 1961 assembly manual shows a shouldered stud. If you know of original 1961 single carb cars that substantiate this please let me know the names of the owners and VIN numbers so that I can have the Technical Information Manual and Judging Guide changed to show this. Right now the TIMJG is somewhat ambiguous about this and some think the change to the shouldered stud did not occur until 1962 model year.
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Re: 1961 Carb Stud for single 4 barrel carb
I believe the shouldered stud was more common to the AFB carburetors as it formed part of the top plate clamping method. I don't believe the WCFB's used or needed it for that purpose.
Stu Fox -
Re: 1961 Carb Stud for single 4 barrel carb
Stu,
Thank you, for your reply. However, the WCFB needs the shoulder just as much as the AFB to serve as the contact point for the underside of the air cleaner lid to prevent over deflecting the air cleaner lid when tightening the wing nut.
MikeComment
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Re: 1961 Carb Stud for single 4 barrel carb
Mike,
If your referring to p/n 3777256, my 1961 s/n 1305 does not have a shoulder,Comment
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Re: 1961 Carb Stud for single 4 barrel carb
Michael;
I wasn't aware that there was a concern for the air cleaner lid to seat on the shoulder. What air cleaner do you have? Is that one of the real thin units? I've had a bunch of dual quad WCFB setups but don't recall the need for a shoulder on the stud, but that was many years ago.
Stu FoxComment
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Re: 1961 Carb Stud for single 4 barrel carb
Stu,
Dual quad set-ups don't require the shouldered stud because the air cleaner lid is much stiffer near the outer diameter of the air cleaner lid. But the air cleaner lid is much softer in the center of the air cleaner lid where the air cleaner lid is attached to single 4 barrel carbs like the WCFB and AFB. This is why I believe GM used shouldered carb stud for single 4 barrel carb but was not necessay and therefore not released for dual four barrel set ups (either AFB or WCFB single 4 barrel carb).
Thank you,
MikeComment
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Re: 1961 Carb Stud for single 4 barrel carb
Mike,
I can trace the car back to the mid 70's, but since I am not the original buyer, nothing can be 100% certain. Sorry if I mislead you.Comment
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Re: 1961 Carb Stud for single 4 barrel carb
Las,
Thank you, for your input. This certainly is a difficult one to track down. I believe the shoulder does perform a value added feature to stop over tightening the air cleaner lid. The fact that the GM drawing for the stud shown in the 1961 manual shows a shouldered stud is compelling information to suggest the stud should be a shouldered stud for 1961 single 4 barrel WCFB carburetors. Most everyone agrees the shouldered stud is appropriate for the 1962 AFB single 4 barrel set ups, the only issue is whether the shouldered stud entered production first in 1961 on the WCFB single 4 barrel carb set up. I will continue my quest looking for proof one way or the other.
MikeComment
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Re: 1961 Carb Stud for single 4 barrel carb
All proof aside for original application logic, I would think a simple measurement on your air cleaner using a straight edge across the base and measuring to the underside of the air cleaner center, then duplicating the process on your carb (air cleaner base surface + gasket to the top of the shoulder on the stud) would tell you a lot about the intent of the design engineers - unless you know this for a fact already.
I can see where that may have been possible with the aluminum single 4-barrel air cleaners, but certainly not for any made of steel. My 63 L-76 uses a chrome plated steel air cleaner (unlike the 62) it does not need any shoulder on the stud for that purpose, and I have always considered it's purpose was as I said - for clamping the carb top plate.
Good luck in your quest. Keep us posted.
Stu FoxComment
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Re: 1961 Carb Stud for single 4 barrel carb
Stu,
Yes, the top of the shoulder is clearly positioned to limit the downward deflection of the air cleaner lid. When I take the wing nut off and press downward on the center part of the lid, it almost immediately contacts the top shoulder of the carb stud thereby limiting the downward deflection of the air cleaner lid. There is no question that the shoulder performs this function very nicely and could not have been an accident in the design of the stud. Perhaps I will issue a new thread asking for people who have Bowtie, 1961 single carb cars to check their carb studs to determine if they have a shouldered stud.
MikeComment
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