66 Upper "A" arm nuts

[Scott S.]

Re: 66 Upper "A" arm nuts

If the photo from Matt Lewis's car is the original hardware than that is what I have been saying all along. That is a tall nut with locking washer with no plating on it, just raw steel. Again I rest my case.

- Ron

Ron,

Matt's photo confirms that the tall hex nut and lock washer (both plain finish) were still being used as of April, 1966.

The 1963-1965 AIMs call out this exact configuration, but in the 1966 AIM the lock washer was removed from the drawing, and the part number for the cross-shaft nut was changed to what the GM parts books define as a distorted-thread locking nut. There is nothing in the 1966 AIM Revision Record on this subject, but the page had many Revsions, we only see numbers 9-12. The date for the #9 revision is hard to read on my copy, but in another Thread John Hinckley says it's 8-30-65, so the change from lock washer and tall nut to no lock washer and locking nut occurred ON PAPER fairly early. Clearly it was not implemented for some time.

I realize the AIMs and the GM parts books contain errors, and that untouched original cars would present the best evidence.

Joe Lucia's '69 Corvette (original owner, see posts #3 and #4 above) has the Stover locking-type nut with no lock washer, so the question seems to be, at what time was the change implemented? Joe has mentioned it before, but I don't remember the month his car was built. As it stands, the data points so far suggest the change happened at some point between April 1966 and the build date for Joe's '69.

[John H.]

Re: 66 Upper "A" arm nuts

As it stands, the data points so far suggest the change happened at some point between April 1966 and the build date for Joe's '69.

Scott -

I've never seen a '67 with anything but the Stover lock nuts.

[Michael H.]

Re: 66 Upper "A" arm nuts

I agree. 63 through early 66, high nut and L/washer. Late 66 and all 67, stover/prevailing torque nut without washer.

I think a light plating of grey on the tall nut and washer though.

[Joe L.]

Re: 66 Upper "A" arm nuts

Ron,

Matt's photo confirms that the tall hex nut and lock washer (both plain finish) were still being used as of April, 1966.

The 1963-1965 AIMs call out this exact configuration, but in the 1966 AIM the lock washer was removed from the drawing, and the part number for the cross-shaft nut was changed to what the GM parts books define as a distorted-thread locking nut. There is nothing in the 1966 AIM Revision Record on this subject, but the page had many Revsions, we only see numbers 9-12. The date for the #9 revision is hard to read on my copy, but in another Thread John Hinckley says it's 8-30-65, so the change from lock washer and tall nut to no lock washer and locking nut occurred ON PAPER fairly early. Clearly it was not implemented for some time.

I realize the AIMs and the GM parts books contain errors, and that untouched original cars would present the best evidence.

Joe Lucia's '69 Corvette (original owner, see posts #3 and #4 above) has the Stover locking-type nut with no lock washer, so the question seems to be, at what time was the change implemented? Joe has mentioned it before, but I don't remember the month his car was built. As it stands, the data points so far suggest the change happened at some point between April 1966 and the build date for Joe's '69.

Scott-----

With respect to these nuts and bolts, C2 cannot be compared to C3 since the thread pitch changed for C3. 1963-67 used 7/16-20 whereas 68-82 used 7/16-14. As far as I know, all C3 used the stover-type lock nut of GM #9422300.

[Joe L.]

Re: 66 Upper "A" arm nuts

I agree. 63 through early 66, high nut and L/washer. Late 66 and all 67, stover/prevailing torque nut without washer.

I think a light plating of grey on the tall nut and washer though.

Michael-----


I believe it's a zinc phosphate finish, very similar to that used for the lower rear shock nuts.

[Matt L.]

Re: 66 Upper "A" arm nuts

66 a arm nuts and spark plugs 013.jpg

I agree. 63 through early 66, high nut and L/washer. Late 66 and all 67, stover/prevailing torque nut without washer.

I think a light plating of grey on the tall nut and washer though.

here's a better close up pic of my mid april 66. looks like some dark residue left on the nut. but i honestly don't know how they are supposed to look. i haven't seen any others than mine. but i know this car is very original.

take care,
matt

[Gary B.]

Re: 66 Upper "A" arm nuts

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here's a better close up pic of my mid april 66. looks like some dark residue left on the nut. but i honestly don't know how they are supposed to look. i haven't seen any others than mine. but i know this car is very original.

take care,
matt

Matt,

Your photo shows exactly what was on my July 20 build '66.

Gary

[Gary B.]

Re: 66 Upper "A" arm nuts

...

Regarding the '66 model year, the question in my mind is: was the distorted-thread, Stover-type locking nut ever used during the '66 model year at the upper A-arm location? We know the AIM implies it should have been used from the start of the '66 model year, but that clearly didn't happen. So, does anyone know of an unmollested '66 that has the Stover type nuts at the upper A-arm location?

We've seen examples throughout the '66 model year where tall nuts were used. Why no examples of Stover nuts, unless they were not used?

Gary