Rear spring outer bolts/castle nut

[Joseph E.]

The GM part number (458982) for the rear spring outer bolt obtained through the archives is no longer a valid number. Does any member know if this part number has been superceded and a different number is currently in use? If GM no longer offers the correct length/style bolt, where can one be obtained? The number for the castle nut, 3983037, also obtained through the archives is still a valid number for any who may need to know. Thanks again.

Joe #45420

[Larry M.]

Re: Rear spring outer bolts/castle nut

Joe:

Most of the Corvette Parts Houses stock and sell this bolt and castle nut. Some examples are Long Island Corvette Supply, DR REBUILD, and Paragon Reproductions. However, I am not certain about the bolt headmark.......this may or may not be important to you. If it is, call them and ask.

I wanted the correct 1967 OEM bolts for my car, and called Richard Fortier (former owner of Paragon, now semi-retired). Richard advertises in the DRIVELINE. He has old stock that he reconditions and replates. Cost is reasonable. I purchased reconditioned OEM bolts from him. Highly recommended.

Larry

[Joe L.]

Re: Rear spring outer bolts/castle nut

Joe:

Most of the Corvette Parts Houses stock and sell this bolt and castle nut. Some examples are Long Island Corvette Supply, DR REBUILD, and Paragon Reproductions. However, I am not certain about the bolt headmark.......this may or may not be important to you. If it is, call them and ask.

I wanted the correct 1967 OEM bolts for my car, and called Richard Fortier (former owner of Paragon, now semi-retired). Richard advertises in the DRIVELINE. He has old stock that he reconditions and replates. Cost is reasonable. I purchased reconditioned OEM bolts from him. Highly recommended.

Larry

Larry------


I would be very reluctant to use re-conditioned, used bolts for the outer spring bolt application on 63-82 Corvettes. GM recommended that these bolts be replaced whenever they were removed from the car for any reason. I wholly concur with that recommendation. These bolts incur operational stresses that are quite different than most bolt-clamped systems. If one of these bolts fails, the car will be "stranded" at that location. This actually happened to a friend of mine.

[Ronald L.]

Re: Rear spring outer bolts/castle nut

Probably a part number question for Joe..
The 66 AIM calls for a 3831585 for the rear spring hanger bolt.

What is the difference to the one mentioned above?

[Joe L.]

Re: Rear spring outer bolts/castle nut

Probably a part number question for Joe..
The 66 AIM calls for a 3831585 for the rear spring hanger bolt.

What is the difference to the one mentioned above?

Ronald-----


GM #3831585 was the outer spring bolt used in PRODUCTION for 1963-72 Corvettes. It was also once available in SERVICE. However, it was discontinued in December, 1974 and replaced by GM #351592 which was one of the PRODUCTION bolts used for 1975 Corvettes.

For 1979 the PRODUCTION bolt changed to GM #458982 and it also became the SERVICE bolt for all 1963-78 Corvettes when the GM #351592 was discontinued in July, 1980.

So, what's the difference between these bolts? Well, both the 3831585 and 351592 were supposed to be 6-1/2" long. However, there was a slight difference in the thread length between the two bolts. GM #458982 is supposed to be 6-5/16" long. It also has a slightly different thread length than the previous bolts.

[Ronald L.]

Re: Rear spring outer bolts/castle nut

Joe, thank you! Exactly what I saw in some used un marked parts, of course I need to find the ones discontinued if we follow your earlier advice against reuse as these are not just any other bolt.

[Don L.]

Re: Rear spring outer bolts/castle nut

Guys, on the subject of the spring bolts et al, can someone advise as to original finish for the bolt, cup, washer, castle nut and cotter pin?

Interesting note on the "mortality" of original bolts. Do we know what grade the originals were?

[Larry M.]

Re: Rear spring outer bolts/castle nut

Guys, on the subject of the spring bolts et al, can someone advise as to original finish for the bolt, cup, washer, castle nut and cotter pin?

Interesting note on the "mortality" of original bolts. Do we know what grade the originals were?

Grade 7 (5 slash marks). Mine have a "C" headmark.

Cup and washer are bare steel (and prone to rusting......so some folks satin clearcoat). Bolt should be black oxide or black phosphate.

Larry

[Joe L.]

Re: Rear spring outer bolts/castle nut

Guys, on the subject of the spring bolts et al, can someone advise as to original finish for the bolt, cup, washer, castle nut and cotter pin?

Interesting note on the "mortality" of original bolts. Do we know what grade the originals were?

Don-----

Don------

I believe the original bolts were black phosphate-finished. However, I have seen some bolts that I believed to be original that were dull zinc plated. I have also seen some that were natural steel. The latter seemed to have had machined shanks.

The "cups" (outer retainers) were natural steel. The "washers" (inner retainers) were natural steel. The "castle nut" (actually, a SLOTTED nut; GM rarely used castle nuts) was "plain" finish (sort of a "brownish", as-manufactured finish). Cotter pin was natural steel.

All of the bolts ever used by GM in PRODUCTION or available from them in SERVICE were GM 290M material grade with FIVE radial lines.

[Wayne M.]

Re: Rear spring outer bolts/castle nut

Here's the pair off my 396 -- don't know if previous owners ever replaced. Pics show the limited number of threads and the shoulder on the shank where the threads end; same sort of shoulder under the head.

Please note the "Made in Canada" stamping and (just above) the very faint sylized "CMU" in a flying cartouche on the large washer. These can be seen from underneath, as installed.

[Ronald L.]

Re: Rear spring outer bolts/castle nut

Wayne, How long is the bolt? IMHO the C head mark was the current production part of the mid 70's C3's.

[Don L.]

Re: Rear spring outer bolts/castle nut

Thanks Larry and Joe. I am in the process of R&Ring my spring and took note to Joe's earlier warning against reuse of original bolts. I picked up the spring hardware kit from Paragon and wanted the finishes right. My orig bolts are cad plated. The new ones that came in the kit are black. From Joe's advice, it looks like BOTH cad and black phos are TFP and should score same (?).

Joe, you are amazing! What DON"T you know? VERY impressive and helpful knowledge on details like this. Thank you for being here!!!!

[Wayne M.]

Re: Rear spring outer bolts/castle nut

Wayne, How long is the bolt? IMHO the C head mark was the current production part of the mid 70's C3's.

Ron -- both bolts are 6_3/8", measured from just under the hex head to the tip. This agrees with P&A30 Rev July 30 1965, Gr 7.506: # 3831585, 1/2"-20 6_3/8.

Same Oct '65 P&A30; Same Oct '66 P&A30; Same Oct '67 P&A30.

But then, by my 7-1-69 P&A30B, the description changes [part # remains 3831585] but size goes to 9/10"-18 --6 1/2", and remains so thru 10-1-69 P&A30 and 1-1-70 of P&A30B. To me, this bolt size doesn't make sense.

Another thing -- when I screw the castle nut to finger tight against the collar, then back off until nut comes free, it takes 11_1/2 turns. Also, I'd say these are zinc or cad plated; the finish is well protected against the elements by the rubber cushions.

[Ronald L.]

Re: Rear spring outer bolts/castle nut

Wayne, The same for the '74 edition, 63-72 Corvette gets the bolt you show under that same part number. 73-4 were different.

The later 70's part had a special zinc based coating that was very corrosion resistant, 400 hour salt spray equivalent. Good stuff, probably not the same part as back in 1966.

Joe - do we know what the thread length difference were?

[Joe L.]

Re: Rear spring outer bolts/castle nut

Wayne, The same for the '74 edition, 63-72 Corvette gets the bolt you show under that same part number. 73-4 were different.

The later 70's part had a special zinc based coating that was very corrosion resistant, 400 hour salt spray equivalent. Good stuff, probably not the same part as back in 1966.

Joe - do we know what the thread length difference were?

Ronald------


I used to know; I actually obtained most of the bolts and measured the differences. however, I do not recall what I did with the notes.