1966 A-Arm Adjustment bolt nuts

[R N.]

Hi Everyone,

Making reference to the 1966 Technical & Judging Manual, it states that the nuts used for the bolts for the upper A-arms adjustments are tall. Can someone tell me from the photo attached if the one in the photo is a period production part? The nut measures approx. 7/16" tall.

The lock washes also appear thicker than a standard lock washer.

[Michael H.]

Re: 1966 A-Arm Adjustment bolt nuts

Kurt,

The nuts and dimensions (7/16") that you have are correct for the nuts for all 63 to mid 66 production. It is a special nut, called a Hi-Nut, or High Nut. They're taller than conventional nuts.
The original plating would have been light/medium grey.

At some point in 66 production, the Hi-Nut and lock washer was replaced with a prevailing torque nut without lock washer.

[Gene M.]

Re: 1966 A-Arm Adjustment bolt nuts

Just to add to Mike's response the lock washers are normally without hash marks around the outside diameter.

[Alan D.]

Re: 1966 A-Arm Adjustment bolt nuts

Not around the outside per Gene however do exist on the inside (at least for one March 64 car).

[Matt L.]

Re: 1966 A-Arm Adjustment bolt nuts

[QUOTE=Michael Hanson (4067);675475]Kurt,

The nuts and dimensions (7/16") that you have are correct for the nuts for all 63 to mid 66 production. It is a special nut, called a Hi-Nut, or High Nut. They're taller than conventional nuts.
The original plating would have been light/medium grey. At some point in 66 production, the Hi-Nut and lock washer was replaced with a prevailing torque nut without lock washer.[/QUOTE

hi guys,
here are a couple pics for comparison of two very original low mile cars. the square pic is of a 7,000 VIN era and the round is of my 19,000 era. my question,if i may add, is when did they switch from square to round? was it about the same time with the switch of the nuts?
take care,
Mattelios 66 corvette 425 12,000 mile 320.jpg
66 vette exhaust clamps 1173.jpg

[Gary B.]

Re: 1966 A-Arm Adjustment bolt nuts

All,

The original upper A-arm nuts on my Jul 20 build date '66 are also the tall ones like Matt and others show. I don't know when the prevailing torque nuts became universally used, but it was after my 7/20/66 car. I think the "mid-66" date for the switch has to be revised, or at least made clear it wasn't a universal switch.

Gary

[R N.]

Re: 1966 A-Arm Adjustment bolt nuts

Is there a source for these hi-nuts? I have the correct nuts on the drivers side, but need two for the passenger side as someone must of changed them out.

[Joe L.]

Re: 1966 A-Arm Adjustment bolt nuts

Is there a source for these hi-nuts? I have the correct nuts on the drivers side, but need two for the passenger side as someone must of changed them out.

Kurt------

I believe Dr. Rebuild or Paragon has them available as a kit.

[Edward J.]

Re: 1966 A-Arm Adjustment bolt nuts

Just to add to Mike's response the lock washers are normally without hash marks around the outside diameter.

Gene, maybe you'll know, I was told that the coin (serrated) style washers were not used on the Mid year cars During the judging of my 63. Yet my 63 does have some in a few places. They appeared to be original on the front suspension lower arms and there were also on 63 only hood blocks. Is this statement I was told hold to be true? Thanks Ed

[Gene M.]

Re: 1966 A-Arm Adjustment bolt nuts

Ed,
One thing I've learned is never say never. But to answer your question in general the practice of washer fabrication in the day was without the tool marks of todays lock washers. But as we know GM had a lot of suppliers of nuts, bolts, washers, etc. The later 60's time period could allow for lock washers with tool serration marks around the outside diameter. I would say the serrated marked lock washers were NOT of general normal usage, but yes possible from the late 60's availability. As hardware shipped in to GM would be more questionable. Some suppliers may have been more progressive in tooling development.

I do not endorse you use serrated lock washers on your restoration because of the lesser possibility of it being original usage. A '63 would be even more questionable with serrated lock washers.

I have seen the marks on the larger lock washers on chassis components but cannot confirm the originality.