Grade 7 bolt

[David B.]

Re: Grade 7 bolt

Normally, an engineering change would have been necessary, but candidly, plants tended to substitute parts first and then ask for permission later, so you might see a substitute in instances where the design parts were in short supply or had a quality problem.

As a personal opinion only I do not believe GM would substitute a grade 8 bolt when a grade 7 would accomplish the desired job performance. All parts are engineered for specific bolt usage. To substitute without Engineering approval would probably involve a cost increase from grade 7 to 8 in addition to a change in recommended torque specs that the line worker would have to be aware of.

[Michael G.]

Re: Grade 7 bolt

Well, you’re are welcome to your opinion, but as an ex-GM fastening engineer, my long experience says that back then the plant did what it wanted, when it wanted, and worried about documenting it (or not) later. Furthermore, the cost difference between a Grade 8 and 7 is negligible, (probably not a concern to the plant), the Grade 7 torque spec would probably be just fine for a Grade 8, and line workers typically had no clue what the torque spec was. Merry Christmas.

[Richard M.]

Re: Grade 7 bolt

My thought earlier was substituting a Grade 7 where a Grade 5 would be specified in the AIM. That's what made me think of it and why I posted at first, thinking John Hinckley used to remind us all of the term at the plant if parts were in short supply. Shut the line down or get something that works on it.

Rich

[Joe L.]

Re: Grade 7 bolt

Well, you’re are welcome to your opinion, but as an ex-GM fastening engineer, my long experience says that back then the plant did what it wanted, when it wanted, and worried about documenting it (or not) later. Furthermore, the cost difference between a Grade 8 and 7 is negligible, (probably not a concern to the plant), the Grade 7 torque spec would probably be just fine for a Grade 8, and line workers typically had no clue what the torque spec was. Merry Christmas.

Michael------

In the case of the spring bolts, applied torque would be irrelevant. For these bolts, the slotted nut is merely turned down by hand to the stop and backed off enough to install the cotter pin.

[Michael G.]

Re: Grade 7 bolt

Hi Joe, thanks, you are correct about the spring bolts, I was thinking more about the harmonic balancer bolt. In either case, either strength would work fine, assuming they are real U.S. made bolts. Otherwise, all bets are off. All the best for your Holiday, Mike

[David B.]

Re: Grade 7 bolt

Thanks David, I understand. But on the line I think it's possible they did whatever was needed to make the cars and not stop the line. Maybe not in this case, true. But I still need to find a detail specifically showing the part# James posted is spec'd as a Grade 7(GM-290-M), not Grade 5(GM-280-M).

Thanks James. Now on the hunt..... gmpartswiki was no help but I have some other big books in the shop I'll check when time.

====

If there are any other part numbers relating to this issue please post them and I'll look those up too.

Rich

Rich, Had to dig into old print files and found 3831585 listed on '67 Corvette rear suspension layout print L-83422 (6-27-66) it is described as:
Bolt 3831585 special 9/16-18 fine thread rolled only mat 290M

[Richard M.]

Re: Grade 7 bolt

Rich, Had to dig into old print files and found 3831585 listed on '67 Corvette rear suspension layout print L-83422 (6-27-66) it is described as:
Bolt 3831585 special 9/16-18 fine thread rolled only mat 290M

Perfect! Thanks David.

I looked through my Standard Parts Catalogs, one from 1966. No 3831585 listed. Then it came to me... it wasn't a "standard" bolt, because of its unique configuration, so I gave up.

You solved for me. Thank You. So in this case, my theory didn't hold water.

Rich

[Richard M.]

Re: Grade 7 bolt

Going off on a bit of a side road here from the original Grade 7 subject, but thought it may be interesting to some.....

A bit more research on the 3831585 outer spring bolts, since it became a bit of a obsession to me lately, and thankfully David cleared it up. His data on the print says it's 9/16"-18. They are this size and in fact Grade 7(GM-290M), at least in 1966/67, and I'm questioning it because of more data I've seen.

Here is the 1962 P&A Catalog. Note the size of 3831585: It is noted as 1/2"-20, 6 3/8"L. Now I would think if the size and TPI of a bolt would change, then it would require a new print, no? Either that or the P&A is wrong.... a good possibility, I suppose.
62PA30_1065_3831685Dimensions.jpg
Above note:
62PA30_1065_3831685DimensionsZoom.jpg
Also, it appears that "maybe" very early 1963 cars, "possibly", did not use the 3831585. Note this is merely speculation on my part, but I suppose it's possible that early '63 used spring bolts 3817584. I could find no other reference to this part#, other than it was replaced by 3831585 in November of 1962. Could it have been used on other cars, yes, and not related to Corvette, yes, but just a may have been related. I checked my 1963 AIM and no reference to a change, but early on who knows what changed and those early AIM pages got tossed. Production of '63's had been going on for a few months by November, and it usually took several weeks before a part change happened on the production floor.

P&A Feb 1961 (But note the date of changeover: 11-62)
6330_2088_3817584_to_3831585.jpg
Above note:
6330_2088_3817584_to_3831585Zoom.jpg

Again, I could find no data on 3817584. It's not a Standard Part. All I found were part change references.

Later on these bolts changed again. In Dec of 1974 3831585 was changed to 351592, then in 1981 351592 changed to 458982.

And another interesting find while searching 351592, up pops the 1978 Corvette AIM pages showing three different bolt part numbers used for various suspension options. 351591, 351592(Base), 351593. Bolt lengths not shown. Interesting it took so long to get ride height figured out.
78VetteAssy-534.jpg

Rich
=====

[Joe L.]

Re: Grade 7 bolt

Going off on a bit of a side road here from the original Grade 7 subject, but thought it may be interesting to some.....

A bit more research on the 3831585 outer spring bolts, since it became a bit of a obsession to me lately, and thankfully David cleared it up. His data on the print says it's 9/16"-18. They are this size and in fact Grade 7(GM-290M), at least in 1966/67, and I'm questioning it because of more data I've seen.

Here is the 1962 P&A Catalog. Note the size of 3831585: It is noted as 1/2"-20, 6 3/8"L. Now I would think if the size and TPI of a bolt would change, then it would require a new print, no? Either that or the P&A is wrong.... a good possibility, I suppose.
[ATTACH=CONFIG]120121[/ATTACH]
Above note:
[ATTACH=CONFIG]120125[/ATTACH]
Also, it appears that "maybe" very early 1963 cars, "possibly", did not use the 3831585. Note this is merely speculation on my part, but I suppose it's possible that early '63 used spring bolts 3817584. I could find no other reference to this part#, other than it was replaced by 3831585 in November of 1962. Could it have been used on other cars, yes, and not related to Corvette, yes, but just a may have been related. I checked my 1963 AIM and no reference to a change, but early on who knows what changed and those early AIM pages got tossed. Production of '63's had been going on for a few months by November, and it usually took several weeks before a part change happened on the production floor.

P&A Feb 1961 (But note the date of changeover: 11-62)
[ATTACH=CONFIG]120122[/ATTACH]
Above note:
[ATTACH=CONFIG]120123[/ATTACH]

Again, I could find no data on 3817584. It's not a Standard Part. All I found were part change references.

Later on these bolts changed again. In Dec of 1974 3831585 was changed to 351592, then in 1981 351592 changed to 458982.

And another interesting find while searching 351592, up pops the 1978 Corvette AIM pages showing three different bolt part numbers used for various suspension options. 351591, 351592(Base), 351593. Bolt lengths not shown. Interesting it took so long to get ride height figured out.
[ATTACH=CONFIG]120124[/ATTACH]

Rich
=====

Rich------


The spring end bolts were 9/16-18 from at least later 1963 right through 1982. As you speculate, it is possible that early 1963 used a different bolt. The GM #3831585 part number does not look to me like a part number that would have been released as early as start of PRODUCTION for the 1963 model year. With respect to the 1962 catalog, the bolt size is incorrect. I believe it's an "anachronism". This often happens with information in the parts description column of the P&A catalogs when a part for n application changes. It also strongly implies that the ORIGINAL 1963 bolt was 1/2-20.

1973+ Corvettes did use different length bolts in order to insure correct bumper height. However, only the standard length bolts were ever available in SERVICE.

I will offer more info on this bolt issue later. I don't have the time right now.

[Richard M.]

Re: Grade 7 bolt

Rich------


The spring end bolts were 9/16-18 from at least later 1963 right through 1982. As you speculate, it is possible that early 1963 used a different bolt. The GM #3831585 part number does not look to me like a part number that would have been released as early as start of PRODUCTION for the 1963 model year. With respect to the 1962 catalog, the bolt size is incorrect. I believe it's an "anachronism". This often happens with information in the parts description column of the P&A catalogs when a part for n application changes. It also strongly implies that the ORIGINAL 1963 bolt was 1/2-20.

1973+ Corvettes did use different length bolts in order to insure correct bumper height. However, only the standard length bolts were ever available in SERVICE.

I will offer more info on this bolt issue later. I don't have the time right now.

Great Thanks Joe. I sensed you'd add more info. Take your time, I'd like to hear all of your knowledge when you get around to it.

Rich

[Gary B.]

Re: Grade 7 bolt

Rich,

As I suspected, Joe Lucia gives a detailed history of the complex history of the rear spring end bolts.

https://www.forums.ncrs.org/showthre...4832#post24832

Some of the sequential part number bolts you list are stated by Joe as having different lengths, to raise or lower the rear ride height.

GM 3817584 I also can find listed nowhere. I suspect it was a production-only item.

Gary

[Richard M.]

Re: Grade 7 bolt

Rich,

As I suspected, Joe Lucia gives a detailed history of the complex history of the rear spring end bolts.

https://www.forums.ncrs.org/showthre...4832#post24832

Some of the sequential part number bolts you list are stated by Joe as having different lengths, to raise or lower the rear ride height.

GM 3817584 I also can find listed nowhere. I suspect it was a production-only item.

Gary

Ah, Great read, Yikes 23+ years ago!

I also liked Duke's comment in post 9, asking Joe to take his laptop and RF modem with him when he went on vacation. I chuckled.

But you know, Joe's been away from home before, like in Italy a few times, and he always checked in with us but said he was far from his documentation and it'd have to wait. Such dedication is amazing.

Rich

[Joe L.]

Re: Grade 7 bolt

Finally, back to this for a little more:

First, some photos of the GM #351592 spring bolt bolt used in PRODUCTION for 1975-E1977 and the GM #458982 used in PRODUCTION for L1977-82 Corvettes (and, SERVICE for 1963-82)

DSCN4361.jpgDSCN4362.jpgDSCN4363.jpgDSCN4364.jpgDSCN4365.jpgDSCN4367.jpg


For many years I have believed that the rear spring end bolts were the only bolts of GM 290-M used on a Corvette at any location. But, as a result of this thread, I discovered that there was at least one other application for a GM 290-M bolt on a Corvette----the big block balancer bolt. So, I decided to research this further. What a time I had coming up with that! More on that later.

[Richard M.]

Re: Grade 7 bolt

Great research Joe!

Rich

In Appreciation of Joe Lucia

[Joe L.]

Re: Grade 7 bolt

Great research Joe!

Rich

In Appreciation of Joe Lucia

Rich------


You will also note that the 1975-E1977 bolt, GM #351592, was a very special bolt in several ways. First, of course, is that it was a GM-290-M grade bolt which, as I mentioned, was a very unusual material grade bolt used on a Corvette. Second, note that the shank of the bolt appears to have been machined rather than die-forged and in natural machined metal finish. Third, note that the head of the bolt has the last 2 digits of the part number embossed in the center. I expect that this was done to differentiate the slightly different length bolts used in PRODUCTION for these years with the other bolts having their last 2 digits embossed.

I wonder if the 1975-77 JG makes note of this?