J56 Option on a C2

[Robert K.]

I have removed these piston assemblies from my car (after sitting a number of years). They are in need of some help......
I've done a search of the archives and found quite a bit of information on the above subject however, I have a few more questions that I didn't find information on.

Questions:
1) What material are the pistons made of?
2) Is there an acceptable solvent to "clean" them? I have soap and water and then after drying thoroughly, used brake fluid to get them to the condition shown.... Does anyone know of another produce/cleaning agent that could be used to remove the corrosion however, not attack the material?
3) I have attached two pictures of two different pistons - one is in ok shape while the other "needs some help"? Does the piston ever come in contact with the inside of the piston cylindar or is the "sealing" done by the seals, i.e. does anyone know of the engineering clearances or where I might find them?
4) Could I just "dress up" the outer face of the one piston that "needs some help" with 000 steel wool and what is your opinion on the functionality?
5) Are the seal kits still available for these pistons (the data shown on the seal face is "5465979 DELCO MORAINE B1 34 while another seal has "5465979 DELCO MORAINE B1 25".
6) Finally, all of the springs are pretty much of the same length telling me that they're all bad or all good!! Does anyone know of the "free length" of these springs from the factory? Are these springs still available?

Thanks for your help!

[Chris W.]

Re: J56 Option on a C2

I have removed these piston assemblies from my car (after sitting a number of years). They are in need of some help......
I've done a search of the archives and found quite a bit of information on the above subject however, I have a few more questions that I didn't find information on.

Questions:
1) What material are the pistons made of?
2) Is there an acceptable solvent to "clean" them? I have soap and water and then after drying thoroughly, used brake fluid to get them to the condition shown.... Does anyone know of another produce/cleaning agent that could be used to remove the corrosion however, not attack the material?
3) I have attached two pictures of two different pistons - one is in ok shape while the other "needs some help"? Does the piston ever come in contact with the inside of the piston cylindar or is the "sealing" done by the seals, i.e. does anyone know of the engineering clearances or where I might find them?
4) Could I just "dress up" the outer face of the one piston that "needs some help" with 000 steel wool and what is your opinion on the functionality?
5) Are the seal kits still available for these pistons (the data shown on the seal face is "5465979 DELCO MORAINE B1 34 while another seal has "5465979 DELCO MORAINE B1 25".
6) Finally, all of the springs are pretty much of the same length telling me that they're all bad or all good!! Does anyone know of the "free length" of these springs from the factory? Are these springs still available?

Thanks for your help!

The pistons are Alumunum that has been hard anadozed. The corroaded one shows the corrosion has gone thru the anadozing. This really will not be a problem if the surface the seal contacts on the pistion is good and free of pits or corrosion.

You can use Brake Clean Spray Cleaner, Lacquor Thinner (carefully) or even spray Carburator Cleaner on the bare metal parts. Some very fine steel wool is just fine but be sure to throully clean everything before you assemble.

The sealing surface, where the inner lip of the seal contacts the piston is the most critical area as far as sealing is concerned. If this surface is pitted, replace the piston as you will have on going sealing problems.

I believe Seal Kits and may be pistons may be available as a replacement part thru your Auto Parts store. I am not sure if GM offers any of these parts anymore.

The springs are usually not a problem as they really do not do much but you need them to ensure the pads are always in contact with the rotors.

BE SURE to check the bores in the caliper castings. If a bore is pitted, you will have sealing problems. Then it would be time for S/S Sleeved Calipers.

Brake fluid is OK for assembly but see if you can find a bottle of Brake Assembly Lube at your parts store. This stuff is much better.

I hope this helps,

Chris

[Joe C.]

Re: J56 Option on a C2

I have removed these piston assemblies from my car (after sitting a number of years). They are in need of some help......
I've done a search of the archives and found quite a bit of information on the above subject however, I have a few more questions that I didn't find information on.

Questions:
1) What material are the pistons made of?
2) Is there an acceptable solvent to "clean" them? I have soap and water and then after drying thoroughly, used brake fluid to get them to the condition shown.... Does anyone know of another produce/cleaning agent that could be used to remove the corrosion however, not attack the material?
3) I have attached two pictures of two different pistons - one is in ok shape while the other "needs some help"? Does the piston ever come in contact with the inside of the piston cylindar or is the "sealing" done by the seals, i.e. does anyone know of the engineering clearances or where I might find them?
4) Could I just "dress up" the outer face of the one piston that "needs some help" with 000 steel wool and what is your opinion on the functionality?
5) Are the seal kits still available for these pistons (the data shown on the seal face is "5465979 DELCO MORAINE B1 34 while another seal has "5465979 DELCO MORAINE B1 25".
6) Finally, all of the springs are pretty much of the same length telling me that they're all bad or all good!! Does anyone know of the "free length" of these springs from the factory? Are these springs still available?

Thanks for your help!

I agree with much of the good advice that Chris W has given, with one exception:
If the anodizing on the pistons is compromised in any way, the pitting process will become accelerated, which will cause leaks in the near future. I suggest replacing the pistons along with the seals/boots, springs, etc....................if these parts are still available.

If the pistons are pitted in a non critical area (anyplace other than inside the sealing grooves), and are no longer available, then have them stripped and re anodized. If they are pitted within the grooves, then they are junk.

[Joe L.]

Re: J56 Option on a C2

I have removed these piston assemblies from my car (after sitting a number of years). They are in need of some help......
I've done a search of the archives and found quite a bit of information on the above subject however, I have a few more questions that I didn't find information on.

Questions:
1) What material are the pistons made of?
2) Is there an acceptable solvent to "clean" them? I have soap and water and then after drying thoroughly, used brake fluid to get them to the condition shown.... Does anyone know of another produce/cleaning agent that could be used to remove the corrosion however, not attack the material?
3) I have attached two pictures of two different pistons - one is in ok shape while the other "needs some help"? Does the piston ever come in contact with the inside of the piston cylindar or is the "sealing" done by the seals, i.e. does anyone know of the engineering clearances or where I might find them?
4) Could I just "dress up" the outer face of the one piston that "needs some help" with 000 steel wool and what is your opinion on the functionality?
5) Are the seal kits still available for these pistons (the data shown on the seal face is "5465979 DELCO MORAINE B1 34 while another seal has "5465979 DELCO MORAINE B1 25".
6) Finally, all of the springs are pretty much of the same length telling me that they're all bad or all good!! Does anyone know of the "free length" of these springs from the factory? Are these springs still available?

Thanks for your help!

Robert-----

First of all, unless the car is an early 1967, these are not J-56 pistons. These are 1st design pistons used for ALL 1965-E1967 Corvettes regardless of whether they had standard brakes, J-50 power brakes or J-56 power brakes. Later 1967 through 1975 with J-56 brakes used a different configuration insulated piston which was unique to J-56.

As far as these pistons are concerned, I would not recommend re-using them. As others have mentioned, these pistons are hard-anodized. The large diameter area of the piston (which evidences wear and corrosion in your photo) is a critical area. The effective seal of the system is a function of many things. However, two of the most important are the chevron seal (the "rubber" seal) and this large diameter area of the piston. These must be in perfect shape to withstand the high pressure of the braking system without leaking.

1965-82 Corvette brake pistons, both 1st design and 2nd design, are no longer available from GM. However, they are available in the aftermarket. The 1st design are a lot harder to find but I believe they are available from Lone Star Caliper as well as others. They are a lot more expensive than 2nd design, though. You can transfer your insulators from the old pistons to the new.

Rebuild kits which include seals and boots ar easily available. Springs are available, too, although I seriously doubt that yours needs replacing unless they suffer from corrosion damage.

[Patrick H.]

Re: J56 Option on a C2

Robert-----

First of all, unless the car is an early 1967, these are not J-56 pistons. These are 1st design pistons used for ALL 1965-E1967 Corvettes regardless of whether they had standard brakes, J-50 power brakes or J-56 power brakes. Later 1967 through 1975 with J-56 brakes used a different configuration insulated piston which was unique to J-56.

As far as these pistons are concerned, I would not recommend re-using them. As others have mentioned, these pistons are hard-anodized. The large diameter area of the piston (which evidences wear and corrosion in your photo) is a critical area. The effective seal of the system is a function of many things. However, two of the most important are the chevron seal (the "rubber" seal) and this large diameter area of the piston. These must be in perfect shape to withstand the high pressure of the braking system without leaking.

1965-82 Corvette brake pistons, both 1st design and 2nd design, are no longer available from GM. However, they are available in the aftermarket. The 1st design are a lot harder to find but I believe they are available from Lone Star Caliper as well as others. They are a lot more expensive than 2nd design, though. You can transfer your insulators from the old pistons to the new.

Rebuild kits which include seals and boots ar easily available. Springs are available, too, although I seriously doubt that yours needs replacing unless they suffer from corrosion damage.

Vette Brakes has the first design pistons.

[Robert K.]

Re: J56 Option on a C2

Thank you to all who replied! I appreciate all the help!

For Joe Lucia......
My car is a Jan. '67 car and I have the tank sticker and other original documentation which show the J56 option among other Hi-Performance items...I do understand your comment tho' and appreciate you making it.

My front pistons are a larger diameter than those that are on the rear. I understand that the rear brakes on a J56 optioned car were the "standard" brake/caliper setup (single pin) while the front brakes were the dual pin (which I have). What was the reason for the larger diameter pistons on the front? Was it strictly a function of the additional pressure needed for the required "stopping power" in these hi performance cars?

One final question:
On a J56 optioned car like this, are the pistons/seals on the rear brakes any different than a standard i.e. (non-J56 optioned car) so that I could just order the "standard" pistons from Vette Brakes?

[Jim T.]

Re: J56 Option on a C2

My original owner 68 and 70 are equipped with front calipers from the factory with larger pistons than the rear calipers. As far as I know, all the 65-82 disc brake Corvettes have the same.
Your rear brake pistons and seals should be the same as other disc brake 65-82 Corvettes.
My 70 with power brakes still impress me today with their stopping performance.

[Terry M.]

[Joe L.]

Re: J56 Option on a C2

Thank you to all who replied! I appreciate all the help!

For Joe Lucia......
My car is a Jan. '67 car and I have the tank sticker and other original documentation which show the J56 option among other Hi-Performance items...I do understand your comment tho' and appreciate you making it.

My front pistons are a larger diameter than those that are on the rear. I understand that the rear brakes on a J56 optioned car were the "standard" brake/caliper setup (single pin) while the front brakes were the dual pin (which I have). What was the reason for the larger diameter pistons on the front? Was it strictly a function of the additional pressure needed for the required "stopping power" in these hi performance cars?

One final question:
On a J56 optioned car like this, are the pistons/seals on the rear brakes any different than a standard i.e. (non-J56 optioned car) so that I could just order the "standard" pistons from Vette Brakes?

Robert-----


On a J-56-equipped 66-E67 Corvette, the front and rear pistons are exactly the same as all other 1965-E67. There is only one type of 1st design piston and that is what you have.

The OD of the front pistons (1-7/8") and rear pistons (1-3/8") is the same for ALL 65-82 Corvettes. It doesn't matter what brake system the car has.

The only difference between J-56 and non-J-56 calipers for any given year is that the J-56 front calipers have the pin boss machined off and and holes added on the caliper ends. The rear calipers are the same.

For 65-E67, the pistons are the same regardless of braking system, but different than any later piston. For L67-75, the J-56 pistons are different than non-J-56.

[Robert K.]

Re: J56 Option on a C2

Joe,

Thank you for the explanation. So the real difference of the J56 option then is the pads (being on an inconel backing plate and semi-metallic) and the proportioning valve setup?

Sorry for all the questions Joe.......

Bob

[Wayne M.]

Re: J56 Option on a C2

Joe,

Thank you for the explanation. So the real difference of the J56 option then is the pads (being on an inconel backing plate and semi-metallic) and the proportioning valve setup.

Bob

Bob -- I'm sure you know this already, but here's 2 pics of the front J56 pads with the inconel backing, the pins, and some instructions that come in the box.

[Robert K.]

Re: J56 Option on a C2

Wayne,

Great pictures - Thank You! I wish that mine looked like that however, they are worn at an angle - probably as a result of a piston "sticking", hanging up, etc.