C2 J65 Brakes (for Duke Williams)

[Larry M.]

Duke - In Jan 2002 you asked me a question. I very slow to respond but I just got back into this car - another car had my attention. You asked that I email the drum numbering.

I have a 64 FI Coupe documented by window sticker and bill of sale and discussion with the original owner of 25 years. 38k original miles. I believe the brakes to be original. Lead shoes have three sets of dual metallic pads and trailing shoes have six sets of dual pads (rear may be only five - didn't repull the tire/drum). Wear seems consistent with 38k based on your prior advice of over 100k on shoes/drums. The drums are 3828671 - W6 on front and 3828688 - W12 left and W3 right on rear. Front drums have round wire anti squeak spring on left and flat wire spring on right. No springs on the rear. All four axels or hubs have "generous" white paint which I believe to be inspection marking and there is some on this white on three if not all four of the drums. Per your response way back then I looked for Max Diameter FMVSS tags - none found. Do these numbers support my view that the brakes are original? I'm guessing they are the same as non metallic brake cars per some earlier responses but potentially original and not replacements. Thanks for your comments/advice.

[Duke W.]

Re: C2 J65 Brakes (for Duke Williams)

Yes, it sounds like you have a completely original J-65 system. J-65 included the segmented metallic shoes, pull back springs that were heat treated to a higher hardness for more temperature resistance, and drums with a finer finish.

The front 671 castings are unique to J-65 because they have slightly greater web thickness than base drums. Base front drum OE casting number is 3830167. The rear 688 OE castings were machined for both base and J-65 applications - J-65 having a finer finish as specified in the '63 Corvette Shop Manual and carried a different end item part number.

Anecdotal evidence on the anti-squeak springs is still somewhat ambiguous, but it could be they were only used on the front, and it appears that both the round and rectangular section wire was used in that era.

Everything you report screams ORIGINAL! You may have a Bowtie candidate.

Since J-65 shoes are so long lived, the drums and shoes will typically outlast the hydraulics. GM never told us to change the hygroscropic fluid, so over the years moisture absorbtion causes internal corrosion and eventually leaks.

I would advise you to inspect the fluid condition. If it looks like old coffee, siphon out the M/C reservoir and scape the crude out from the bottom and clean thoroughly with fresh brake fluid. Then flush a quart of DOT 4 fluid through the system.

If you want to be sure that the brakes are always there, remove the m/c for a rebuild and all the wheel cylinders for either rebuild or replacement. The 1 3/16" front and 1" rear wheel cylinders are common to Chevrolet full size passenger car drum brake systems of the era, and are readily available and inexpensive.

Mark the shoes and drums for reinstallation in the same location, and simply clean everything up and reinstall with the new or rebuilt hydraulics. Flush the system every two to three years and it will likely outlive all of us.

Thanks for the follow-up!

Duke

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

Larry,

Thanks for the info on the brakes. Wonder if it would be possible to get a dimension from you on the drums. Need the thickness of the web, or face section, of a front drum, if you happen to have a caliper or micrometer handy. Other than the original machining, this is supposed to be the ONLY difference between standard and metallic front drums. Even the casting number is the same. Thanks.

[Larry M.]

Re: C2 J65 Brakes (for Duke Williams)

Michael,

One side is .126 and the other is .128 measured next to the hub opening...now this is on 42 year onld parts, pretty clean on the inside but rust and paint remnants on the out. I'd say they are nominal 1/8 inch. What is the thickness on non metallic drums if you know?

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

Thanks Larry. The dimensions are supposed to be .109"-.119" for the web on standard front drums while the dim on front metallic drums is listed as .125"-.135". Not much difference but, so far, all of the std and met drums that I've checked do indeed fall within their respective dim's. Most std drums come in at around .110" while most met drums are usually about .130".

Interesting that the engineers on these cars had absolutely NO idea that people would be inquiring about minute details like this 40 years later.

[Duke W.]

Re: C2 J65 Brakes (for Duke Williams)

I thought we previously ascertained that OE J-65 front drum castings are 3828671 and base are 3830167. Different casting numbers because of the different web...

Duke

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

Duke,

The 3830166 and 3830167 are the original 63 part numbers for the standard and metalic front drum. (can't remember which is which) The 3828671 is the casting number that would be on the ring of both std and met front drums. They both used the exact same outer band, or ring, but with a different web for met. Gets pretty confusing with different part numbers but the same casting number.

[Duke W.]

Re: C2 J65 Brakes (for Duke Williams)

What bothers me is that the same casting number is assigned to TWO different parts out of the mold. How did manufacturing ID the thick web drum for final machining to J-65 spec versus the thin flange drum for final machining to base spec?

Rear drum castings were identical and given end different end item part numbers, which is understandable because of the different friction surface finish, but since the front drum castings were actually different because of the different webs, I don't see how they can have the same number.

Duke

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

Duke,

The ring and the web started life as two separate pieces. They were attached (somehow) and became a brake drum. In that way, one ring, with the casting number, could be used for two different finished parts.

I understand this "two piece" practice was abandoned in favor of a one piece drum some time later.

[Duke W.]

Re: C2 J65 Brakes (for Duke Williams)

My understanding is that the stamped steel web was placed into the mold and the molten iron solidied and bonding to it, so the web is an integral part of the casting. These are known as "composite" drums.

Duke

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

Ok, that makes sense. That would mean the outer ring would always be the same casting number for met/non met drums and just the web was changed. I always wondered how they did that.

[Duke W.]

Re: C2 J65 Brakes (for Duke Williams)

So, once out of the mold, how did they differentiate between the two to be sure that the J-65 castings received the proper finer finish?

My original 671 drums have an "X" stamped on the web, just beyond the bolt hole radius.

Could that be an ID mark to distinguish J-65 front drums?

Duke

[Michael H.]

Re: C2 J65 Brakes (for Duke Williams)

That's a good possibility. There had to be some visual method of separating the std from the met drums after they were mfg'd and that may be how it was done. Also possible that the X was used on the raw web, before it was added to the rim. Maybe we should also be looking for the X on original met drums? I have an NOS pair of frone met's but they're still up in the frozen north. I'll definitely bring these back with me next trip.

I would have guessed a paint stripe of some kind for the completed drum assy as it would have been much easier to see. The NOS pair has only a black coating, if I remember correctly.

[Larry M.]

Re: C2 J65 Brakes (for Duke Williams)

Mike & Duke

My front drums have an X...not hard to find...a big X located outside the bolt circle....oriented differently on the two drums.

[Gordon Peterson #4961]

For What It's Worth...

I have COMPLETELY struck out trying to find anyone who will re-line or otherwise reproduce the metallic J65 (or J56) shoes.

When they finally wear out, that's it for J65, I guess.

Pete