J-56 calipers & master cylinder

[Frank Hare]

I have a silver 435 coupe #7606 that I took apart 17 years ago and just put the body back on and now brakes ,it has the j-56 antilock valve under the propotioning valve and my tank sticker, which is very tattered says it has
j-50&j-56 .
What is the casing number for the j-56 master cylinder with j-50. I was thinking mine was the original till now,almost everything else is, but I guess not. It is a replacement? #5460346 stamped "PG".
Where can you get the j-56 brake pads.Are they still available I called a couple parts stores and no go, My calipers have been changed to vette/brake ground off casings,restamped ss standard one pin type calipers.But was thinking about adding the j-56 calipers back on now that I know about them.Since it came with them originally.
And the rears are just standard nothing different one pin calipers with the
J-56 option? I saw a set of four J-56 calipers front and rear for sale on ebay what car did they come on.
What books can you suggest for reading up on the part numbers for my car, its time to check them out, I guess I need to do some research.
Thanks
Below is a couple pictures of my 67 and 62 #350




My 67 L71 coupe pics

[John H.]

Re: J-56 calipers & master cylinder

Frank -

You have the correct master cylinder (BTW, it's 5480346). J-56 front calipers are hard to find; Long Island Corvette carries the J-56 metallic front and rear pads, about $200 per axle set (rear calipers aren't unique, just the pads).

[Joe L.]

Re: J-56 calipers & master cylinder

Frank and John-----

J-56 caliper castings used for 1967 were exactly the same as those used for standard brakes. The castings all had casting numbers beginning with "545". It is very easy to convert a set of standard front calipers to the J-56 configuration. All that has to be done is to grind off the pad pin bosses and drill the holes on either end for the "twin-pin" cotter pins. This is exactly how Delco-Moraine manufactured the J-56 calipers using the same castings as the standard brakes. In fact, on original J-56 calipers you will see where the pin bosses were machined off.

While it's easy to convert a set of standard calipers to J-56, it's not so easy to convert a set of J-56 calipers to the standard configuration. So, once it's done, it's done.

J-56 rear caliper castings were the same as standard brakes.

J-56 caliper assemblies used for 1967 to 1975 used different pistons, front and rear. The pistons had thick Pyroceram insulators attached to the front of the piston with a center-mounted machine screw. These "2nd design" (1967-75) J-56 pistons are not currently reproduced. So, while the insulators may be re-used if you have them, you won't be able to find pistons to mount them on. The chances that original pistons will be re-usable is nil. However, you can use standard pistons without the insulators (like those used on all non-J-56 brake cars) and it will be very difficult for anyone to detect.

Original J-56 pads used for 1967 were of a special semi-metallic lining material. The front pads, of course, had the reinforcing, curved over upper backing plate and "twin-pin" retention. For 1966-68, the FRONT lining material was rivetted to a steel backing plate; for 69-75, the FRONT lining material was bonded to an Inconel backing plate. All 66-75 REAR J-56 pads had the friction material bonded to a steel backing plate.

[Wayne M.]

Re: J-56 front pads (riveted or bonded)

Joe -- from Chevrolet Service News, May 1966:

"The informatin below will familiarize the technician with the function and maintenance of the 1966 Corvette Heavy Duty Brakes.....the heavy duty brake shoe and lining assemblies differ from the regular production assemblies in that they are BONDED rather than riveted......"

Is it possible that you've mixed this with the change from bonded to RIVETED on the 1966 regular production pads ? Ref. [Field Service Engineering Bulletin, Feb 15, 1966] "starting with VIN S109343 (on front) and on S109688 (both front and rear)...to exhaust parts stock, 51 units built between Serial Nos. S110379 and S110459 had bonded pads installed in the rear brakes"

[Joe L.]

Re: J-56 front pads (riveted or bonded)

Wayne-----

I used to think that all J-56 pad linings were bonded to the backing plate. However, 2 things changed my mind:

1) Awhile back, I purchased a whole bunch of used (about 30 pads with some worn out) J-56 front pads. I purchased them to get the Inconel backing plates used for the 69-75. About 2/3 of the backing plates I got were of the Inconel variety; all of these were bonded. However, about a 1/3 of the pads were steel backing plates with rivetted lining. I believe that these were all original J-56 pads;

2) In old Chevrolet parts references the rear pads used from 66-75 are annotated with the word "(bonded)". The front pads used from 69-75 are also annotated with the word "(bonded)". However, no such term is used to describe the 66-68 front pads.

[Wayne M.]

Re: J-56 front pads (riveted or bonded)

Joe --

Yet, in the 1966 introduction of RPO's M22, F41, J56, N03, in Vol 9 No.4 of Corvette News (must be late in the model year, as they cover the results of the February Daytona 24-hr Continental), they describe the J56 option as: "Brake shoe material is a tough wrought nickel alloy, chosen primarily for its ability to retain strength at elevated temperature .... and is corrosion resistant. Brake shoe rigidity is increased by flanging the top of the shoe"

So it appears (at least from this source) they were INCONEL from the "git-go". If you have riveted carbon steel examples, I would question if they are factory J56.

[William O.]

Re: J-56 calipers & master cylinder

The correct casting number for the J56 is 5480346, additonally your front calibers will have a HD suport bracket 3882783/84

Regards.