Bolt Identification on J56

[Robert K.]

I could use some help on the identification of the bolts shown on the attached pictures.
- pic with "S" and six hash marks - fastens heavy duty support bracket to front suspension (drivers side),
- pic with "S" (or maybe "5") with a dash underneath it and 3 hash marks - fastens the caliper to the front suspension (drivers side),
- pic (wider view) shows these two bolts (the one with the stack of washers underneath it is the one with the 3 hash marks while the other one is below and to the right (drivers side)........
On the other side of the car (passengers side), you see the same bolt head markings for one of the bolts ("S" with 6 hash marks) however, the other bolt (the one which holds the support bracket on) is different and has marking that appear to be a "TR" or a "FR".

1) Any thoughts from anyone which is correct or what these bolts may be?
2) I looked in the AIM and also N. Adams - Volume 2 book and did not see anything mentioned as to the the heavy duty support bracket. Is this shown anywhere in the AIM or Noland's book - perhaps I just missed it. I had thought that this bracket was only on the J56 equipped cars. This is an original J56 car and am in the process of cleaning it up as my work permits. I know that the caliper shown is not correct on the front - I replaced it many years ago with a SS one (still have the old calipers).

[Joe L.]

Re: Bolt Identification on J56

I could use some help on the identification of the bolts shown on the attached pictures.
- pic with "S" and six hash marks - fastens heavy duty support bracket to front suspension (drivers side),
- pic with "S" (or maybe "5") with a dash underneath it and 3 hash marks - fastens the caliper to the front suspension (drivers side),
- pic (wider view) shows these two bolts (the one with the stack of washers underneath it is the one with the 3 hash marks while the other one is below and to the right (drivers side)........
On the other side of the car (passengers side), you see the same bolt head markings for one of the bolts ("S" with 6 hash marks) however, the other bolt (the one which holds the support bracket on) is different and has marking that appear to be a "TR" or a "FR".

1) Any thoughts from anyone which is correct or what these bolts may be?
2) I looked in the AIM and also N. Adams - Volume 2 book and did not see anything mentioned as to the the heavy duty support bracket. Is this shown anywhere in the AIM or Noland's book - perhaps I just missed it. I had thought that this bracket was only on the J56 equipped cars. This is an original J56 car and am in the process of cleaning it up as my work permits. I know that the caliper shown is not correct on the front - I replaced it many years ago with a SS one (still have the old calipers).

Robert-----


First of all, if this is an original J-56-equipped car, it's not now with its original calipers. The caliper pictured is a standard, single pin caliper and not the J-56 dual pin configuration. Also, this caliper has been painted "silver" which is indicative of a commercially rebuilt (and, likely sleeved) caliper.

Second, if the caliper(s) have been replaced, ANYTHING could have occurred with the bolts. Some could be original, others not. I have not seen original bolts (of any size or type from the period) with the "L5" headmarking, but it's possible such bolts were used. It's VERY possible that different bolts were from different manufacturers (and, thus, different headmarkings). The factory did not use bolt heamarkings as a "set". Different size bolts were supplied by different manufacturers.

The reason that you won't find anything about the assembly in question in the AIM is because the front spindles were delivered to St. Louis as an assembly. This assembly included the calipers and attaching parts. Of course, the J-56-equipped cars used a different ASSEMBLY than non-J-56. I doubt there will be much more in Noland's book about this, either. Furthermore, the 7/16" size bolts for the front spindle-to-steering arm were never specified in SERVICE for 66-68 Corvettes with J-56. So, there's no help there, either. The only way we could know more about these bolts would be to have the specs/drawings for the GM #3899109 and 3899110 steering knuckle assemblies (which were never available in SERVICE) and I don't have those.

The bolt configuration in the photos you've posted do not look original to me. First of all, I find the headmarkings "questionable". Second, I doubt that an SAE grade 5 bolt would have been used for one of the steering knuckle-to steering arm bolts. Third, while it is sometimes necessary to shim the point of attachment of the J-56 bracket to avoid caliper distortion, the shims (washers) are NOT installed as in the photo. The configuration pictured "smacks" more of someone using washers to compensate for an overly long bolt. The factory would NEVER have done that, especially for a steering sytem like this.

[Robert K.]

Re: Bolt Identification on J56

Joe,

Thanks for your reply - I appreciate the time you put in re: your response. A couple of clarifying questions......

1) What do you find "questionable" about the headmarkings?
2) Why do you think that a SAE grade 5 bolt would not have been used in this application? It is a very high stress area, isn't it? The "other" bolt is a grade 8 bolt, isn't it? They were on the car when I purchased it many years ago however, that doesn't mean that they are original..... Is it unusual to find a grade 5 bolt on the caliper for the C2's? The grade 8 bolt is on the heavy duty support bracket......
3) Just for your information, I put the washers on the one bolt many years ago - they did not come that way from the factory....(keen eye, Joe!).....

Do you have any other leads/sources that I might look into as to what type of bolts came with this arrangement?

Would anyone else out there have a picture of this front assembly of a '67 with J56 brake option?

[Joe L.]

Re: Bolt Identification on J56

Joe,

Thanks for your reply - I appreciate the time you put in re: your response. A couple of clarifying questions......

1) What do you find "questionable" about the headmarkings?
2) Why do you think that a SAE grade 5 bolt would not have been used in this application? It is a very high stress area, isn't it? The "other" bolt is a grade 8 bolt, isn't it? They were on the car when I purchased it many years ago however, that doesn't mean that they are original..... Is it unusual to find a grade 5 bolt on the caliper for the C2's? The grade 8 bolt is on the heavy duty support bracket......
3) Just for your information, I put the washers on the one bolt many years ago - they did not come that way from the factory....(keen eye, Joe!).....

Do you have any other leads/sources that I might look into as to what type of bolts came with this arrangement?

Would anyone else out there have a picture of this front assembly of a '67 with J56 brake option?

Robert------


1) I've just never seen the "L5" headmarking on a factory-installed bolt; that's the only thing I found questionable;

2) Generally, these bolts were SAE grade 8. I don't recall what the grade was for 65-67 but for 68+ the bolts were SAE grade 8 (and, the size also increased to 1/2" instead of the 7/16" used for midyears). I would not expect GM to use less than a grade 8 bolt for a critical steering application like this

3) Why did you put the washer stack on the bolt?

[Rich P.]

Re: Bolt Identification on J56

Robert,

The L5 bolt was an add onThat bolt is supposed to be grade 8 The S and TR are assembly line typical for 67-69 cars. The S is usually ther bolt that holds the caliper 1/2's together and the TR is typical of the caliper mount bolt. I have had and sold hundreds of these.

Rich

[Grant W.]

Re: Bolt Identification on J56

[quote=Robert Kerestes (36438);445007]I could use some help on the identification of the bolts shown on the attached pictures.
- pic with "S" and six hash marks - fastens heavy duty support bracket to front suspension (drivers side),
- pic with "S" (or maybe "5") with a dash underneath it and 3 hash marks - fastens the caliper to the front suspension (drivers side),
- pic (wider view) shows these two bolts (the one with the stack of washers underneath it is the one with the 3 hash marks while the other one is below and to the right (drivers side)........
On the other side of the car (passengers side), you see the same bolt head markings for one of the bolts ("S" with 6 hash marks) however, the other bolt (the one which holds the support bracket on) is different and has marking that appear to be a "TR" or a "FR".

Hi Robert

Here is a picture of the M bolt with 6 slashes. It is 2 1/4 long and is 7/16 size with a 5/8th head.
This is one type of bolt that should be inplace of the other bolt with all those incorrect washers.
Hope this helps.
Grant

[Robert K.]

Re: Bolt Identification on J56

Robert------


1) I've just never seen the "L5" headmarking on a factory-installed bolt; that's the only thing I found questionable;

2) Generally, these bolts were SAE grade 8. I don't recall what the grade was for 65-67 but for 68+ the bolts were SAE grade 8 (and, the size also increased to 1/2" instead of the 7/16" used for midyears). I would not expect GM to use less than a grade 8 bolt for a critical steering application like this

3) Why did you put the washer stack on the bolt?

Hi Joe,

Thanks again.....
Many years ago I must not have had a bolt of the correct length and replaced it with a longer one and use the washers as "spacers"!!! It sounds like you and Rich ar both saying that both bolts should be grade 8. It seems curious to me that the other side (marked TR) is a grade 5 bolt......I could have replaced that one, but surely don't remember anymore!!

I appreciate all the help from everyone!!

I'll just ask one more time - Do you know of anywhere that I can find any specs or pictures (other that what you already mentioned in your first reply)??

Bob

[Joe L.]

Re: Bolt Identification on J56

Hi Joe,

Thanks again.....
Many years ago I must not have had a bolt of the correct length and replaced it with a longer one and use the washers as "spacers"!!! It sounds like you and Rich ar both saying that both bolts should be grade 8. It seems curious to me that the other side (marked TR) is a grade 5 bolt......I could have replaced that one, but surely don't remember anymore!!

I appreciate all the help from everyone!!

I'll just ask one more time - Do you know of anywhere that I can find any specs or pictures (other that what you already mentioned in your first reply)??

Bob

Bob----

I suspect the "TR" headmark bolt is original. However, it surprises me that a grade 5 bolt would have been originally used for this application.

I don't understand why you would have replaced the bolt (using the one with the "L5" headmarking and requiring washers) AND now asked if that bolt was original? Obviously, it's not.

I do not know of anyplace to get photos or more information on original bolts for this installation.