66 rear spring cushion bolts

[Mike P.]

Looking for input on rear spring cushion bolt head markings , and finishes . Do the thick cushion washers have any markings, and are they a natural finish. What is finish on slotted nut, cotter key ? From what i have found on the thin cushion washers they are a natural finish. Thanks Mike

[Joe L.]

Re: 66 rear spring cushion bolts

Looking for input on rear spring cushion bolt head markings , and finishes . Do the thick cushion washers have any markings, and are they a natural finish. What is finish on slotted nut, cotter key ? From what i have found on the thin cushion washers they are a natural finish. Thanks Mike

Mike-----


The rear spring end bolts were black phosphate finished. They are a GM 290M material grade bolt and have FIVE radial lines to denote this. They are a trimmed head bolt (i.e. non-"indented") and some typical, but not necessarily only, headmarkings are "C" and "SBC".

The inner cushion retainers (i.e. large flat washers) are NATURAL finish. Vaguely, I recollect that there may have been a manufacturer's ID stamping on them. However, this is entirely moot since such a stamping cannot be seen once the retainers are installed. These retainers have a "rounded" edge and the "rounded" side is to be installed toward the cushion which may seem counter-intuitive to some.

The slotted nut had a PLAIN finish and, for 1964-67 was GM 301M material grade. It was 7/8" across-the-flats and 31/64" thick. It was NOT a castle-style slotted nut; just a standard slotted nut.

The cotter pin was of NATURAL finish.

[Wayne M.]

Re: 66 rear spring cushion bolts

.....The inner cushion retainers (i.e. large flat washers) are NATURAL finish. Vaguely, I recollect that there may have been a manufacturer's ID stamping on them.
The slotted nut had a PLAIN finish and, for 1964-67 was GM 301M material grade. It was 7/8" across-the-flats and 31/64" thick. It was NOT a castle-style slotted nut; just a standard slotted nut..

Here's an example of an original '65 retainer washer (on left), with a '64 on the right. Just one more part of our C2's with a "made-in-Canada" label . The manuf. ID seems to be CMU. As this is on the flat side, it might be visible from the bottom with the nut in place.

Joe -- can you describe a slotted nut (cotter pin type) which is NOT also defined as being of castellated design (ref. Gr 8.917) ?

[Mike P.]

Re: 66 rear spring cushion bolts

Thanks for the pics that is exactly what i have i just wasnt sure abouthe made in canada thing.