67 Corvette Caliper Date Decode

[Patrick B.]

Re: 67 Corvette Caliper Date Decode

Wayne,

It is the opinion of some of us that the numbers you're showing in the casting (eg. 130 in the photo above) are not the date codes. The date codes are stamped in tiny numbers on the top of the caliper, same size and font as the tiny ones for the date code on the master cylinder. On a few cars with original calipers the stamped date codes do seem to line up.

Below is a "136" stamped in a caliper. Sorry for the silver paint which fills in the numbers a bit. My attempt at keeping a "machined look" while preventing rust.

Patrick



Patrick:
Do you have a picture taken a little futher away offering a little more context as to where to look for the stamped numbers on the caliper. My 70 LT-1 actually still has the original calipers as a result of the car being used to evaluate silicon brake fluid in 1974 (when it was still experimental). The calipers have never been sleeved because they are still rust free since the honing in 1974. I examined the left front and did not notice any stamped numbers. The cast numbers are 20 on one side and 15 on the other. These seem to be mold numbers rather than dates, as they don't seem to relate to the car build date of July 3.

aaaaaaaaaaaaaaaaaaaa

[Ronald L.]

Re: 67 Corvette Caliper Date Decode

Patrick, what was the build date of your '70?

Those are casting dates...and they probably coincide pretty good.

Single digit and that circle-star are the pattern numbers.

[Joe L.]

Re: 67 Corvette Caliper Date Decode

Patrick, what was the build date of your '70?

Those are casting dates...and they probably coincide pretty good.

Single digit and that circle-star are the pattern numbers.

Ron------



I don't see the "circle-star" on any of the castings in this thread, assuming that I'm correct in what I think you are referring to.

However, the circle with 6 interior segments often seen on 1st and 2nd design calipers is not a pattern number. It is a foundry identification casting mark. Unfortunately, by itself it does not identify a particular foundry as it is the "generic" casting mark for Central Foundry, a GM division of old which operated quite a few foundries.

In the case of these calipers, the above-referenced casting mark in combination with a "D" often seen elsewhere on the casting denoted the Danville, IL malleable iron foundry.

[Patrick B.]

Re: 67 Corvette Caliper Date Decode

Patrick, what was the build date of your '70?

Those are casting dates...and they probably coincide pretty good.

Single digit and that circle-star are the pattern numbers.

Ronald: The build date of my 70 was July 3. The numbers that I referred to as possible mold numbers were the cast numbers with screw head impressions that look like the casting date on heads and blocks but don't make obvious sense as dates on the calipers. Patrick had found stamped numbers that he thought might be the caliper dates.

[Ronald L.]

Re: 67 Corvette Caliper Date Decode

I'm aware of both and Joe is commenting about 65-E67 pictures where we have now flipped to 70 casting dating.


Joe, you can't mix the two. type 1 or the dating.

Yes, that circle asteric is there on type 1 and is a pattern identifier.

Cast parts have these, especially small parts that were laid out in an array and many poured at once.

Those remaining survivor parts on real cars match very closely and clearly are Julian dates.

Type two 545 and 547 casting have other dating methods and they definitely have dates in them. If one was to look at enough of them, I am sure you could establish the methodology, but you would have to do this casting number by casting number.

Moving on to the stamped in dating it should be located on a top machined surface, will be interesting to know a more specific location as I had an opportunity to sort through a pile of 545-7 calipers for a friend recently and did not see those marks, even on NOS caliper sets.

I am thinking perhaps we need separate threads as my place bolt question is now lost in this fray, as would be the type 1 brake pad rework...

[Joe L.]

Re: 67 Corvette Caliper Date Decode

I'm aware of both and Joe is commenting about 65-E67 pictures where we have now flipped to 70 casting dating.


Joe, you can't mix the two. type 1 or the dating.

Yes, that circle asteric is there on type 1 and is a pattern identifier.

Cast parts have these, especially small parts that were laid out in an array and many poured at once.

Those remaining survivor parts on real cars match very closely and clearly are Julian dates.

Type two 545 and 547 casting have other dating methods and they definitely have dates in them. If one was to look at enough of them, I am sure you could establish the methodology, but you would have to do this casting number by casting number.

Moving on to the stamped in dating it should be located on a top machined surface, will be interesting to know a more specific location as I had an opportunity to sort through a pile of 545-7 calipers for a friend recently and did not see those marks, even on NOS caliper sets.

I am thinking perhaps we need separate threads as my place bolt question is now lost in this fray, as would be the type 1 brake pad rework...

Ron------


I am not aware that 65-82 Corvette calipers were ever available from GM in SERVICE as a complete caliper assembly. They were only available as bare caliper HALVES and could be used to SERVICE an existing caliper assembly or to build up a complete caliper assembly. I believe the stampings pictured in Patrick's photo were applied at the time the complete caliper assembly was manufactured for PRODUCTION. So, I expect that they will only be found on original calipers installed on cars.

I suppose it's also possible that they were stamped on caliper halves at the time of final machining but I doubt it. I have quite a few NOS caliper halves and, one of these days, maybe I'll go through them to see if there are any stamped characters.

Also, I will repeat that the "asterisk within a circle" is NOT a pattern number. It is the casting mark identifying a Central Foundry casting. These marks, usually referred to as the Central Foundry "Wagon Wheel" will be found on many castings produced at GM foundries of the day. Some Central Foundry GM foundries like Saginaw and Tonawanda used the casting mark very infrequently. Others, especially Danville, IL, used it on the majority of castings. Many ALUMINUM castings produced at the Bedford, IN aluminum-only foundry have the "Wagon Wheel", usually in conjunction with a "CFB" (i.e. Central Foundry-Bedford).

Why didn't all the Central Foundry operations use the "Wagon Wheel" on a consistent basis? I have no idea.

[Ronald L.]

Re: 67 Corvette Caliper Date Decode

Joe - Well aware of the logo, the point that the number that is near that logo is being lost - its the sand cast pattern number - separate from the Julian date code. I've found it interesting to note the Muncie 3885010 main cast same pattern # wear from late 65 through 67 to the point I can tell you high degree of certainty that the undated housing you find were service parts.

[Ronald L.]

Re: 67 Corvette Caliper Date Decode

Were are missing the point of my question here - how about the numbers and letters on those place bolts???

[Wayne M.]

Re: 67 Corvette Caliper Date Decode

Wayne,
Are these the head marks you have on your place bolts?

Anyone know what the numbers and letters mean???

Ron -- sorry, I missed this post last night. Was not even aware there were cast figures on the place bolts . Here's the small ones on the rear caliper dated 99 [first thumbnail]. Looks like L and a number (5 ?) on the edge, with the number 8 in the center. Both bolts seem the same. Checked the other rear caliper and would describe those 2 bolts as the same, also.

Checked the fronts and they are the same character size, in spite of the larger bolt head, and again, I see an L and a 7, with small 8 in the middle (or are both L's actually 7's [or vice versa] ? Only one of the 4 front caliper bolts has what I would say an 8 on the circumference, as well as an L, with the 8 in the center.

[Joe L.]

Re: 67 Corvette Caliper Date Decode

Were are missing the point of my question here - how about the numbers and letters on those place bolts???

Ron-----


I don't think there's a whole lot of mystery here. I think the alpha characters on your bolts ("FB") and on Wayne's bolts ("L") represent the manufacturer's ID. The "L" represents Lamson&Sessions, a supplier of fasteners to the automotive industry at the time. I've forgotten what manufacturer that "FB" represents.

In the case of the digits, I expect that the "8" seen on your bolts and on Wayne's represents the material grade (i.e. SAE grade 8 or GM-300M).

I do not know what the remaining 2 digits represents on your bolt head. However, it's likely a manufacturer's code of some sort. Obviously, it was not a GM requirement since it does not appear on Wayne's bolts.