tdkask

Hi, I'm David and I don't have a corvette. I do, however, have a corvette master cylinder in my '80 Jeep CJ7. Apparently it is a popular upgrade to significantly improve the brake system with other drivetrain upgrades. I'm sure the 'vette world gets that a lot.

My problem is that the master cylinder was added before I owned the Jeep and is now bad, but I have no idea what year it is. I have posted a couple pictures below of it installed in my Jeep and hope someone here can ID it so I can get a replacement. Thanks for your help. Have a great day.




Click on pics for larger view.

SmokinBBC

Try this link:

http://www.ecklerscorvette.com/corve...1977-1982.html

Better prices here:

http://willcoxcorvette.com/advanced_...rt=3a&&page=-1

tdkask

I read everywhere I could find before I posted here, but can't tell. Mine has a slightly different casting in the lower front than a lot I'm seeing, as if the sides are symmetrical, whereas some only have the casting on the driver's side. Please see my 3rd and 5th pictures for examples of mine where I'm talking about.

I can get re-manufactured ones for less than $20 locally but likely have to order them, so need to get it right the first time. Thanks for the help.

0Willcox Corvette

TDTask.. email me the casting numbers off the master cylinder.. Willcoxcustomerservice@willcoxcorvette.c om. I'll get you the right one. Tomorrow I'll take a look at your email and cross it over.

kf4cln

Wilcox to the rescue ....again !

tdkask

Thanks. Unfortunately, there are no casting numbers. There are a couple Jeep sites that sell a upgrade kit and employ a "corvette style" mater cylinder. Also, it may have been an off the shelf replacement part from a chain store that just painted the info on instead of cast, so no go there.

I was hoping someone would recognize it as the same as theirs and tell me what year. In the Jeep community forums there is a lot of discussion back and forth as to the best years to use, but generally all are C3 era.

What are the differences? Can one swap with the other from 68-76 or from 77-82 or whatever? This is, of course, assuming I use the one intended for power brakes.

Thanks again for any info. I appreciate it.

gbvette62

Your master cylinder has a different casting, because it's not an OEM Corvette unit.

That's an aftermarket "generic" unit, not a GM Delco MC. Because of this, it's pretty difficult to determine which Corvette MC it may be (if it even is a Corvette one).

There were 3 variations to the 67-82 Corvette dual reservoir MC; the 67-76 manual, 67-76 power and 77-82 all. The main difference is the bore size of the unit.

The booster is of no help either, as it's not from a Corvette, or at lease not one from a 67, 68-76 or 77-82 Corvette.

tdkask

Well, there has been a lot of positive discussion of the "all" which I assume, based on this, is the 77-82 as mentioned above. Thanks gbvette62. I think that as long as it bolts to the booster then I'll be fine. I can lengthen/shorten the rod as necessary. Already the rod is a little too short, but the MC is "spaced" out with nuts between. I think I'll get the '77-'82 and do as necessary to make it all work. One more question, though... are the cylinders the same inside? Is there a difference between which bore is intended for front or rear? I read that in these the front is for front and the rear (closest to firewall) is for rear brakes. Can anyone confirm? Or is it same either way? As mine was adapted to be this way (front-front, rear-rear) it would be beneficial to keep the same configuration. If I had to, though, I could replace the line to proportioning valve just below firewall on frame.

Out of curiosity, is there an aftermarket upgrade or mod beyond these, or is that blasphemous in the Corvette world?

Again, you all have been a tremendous help.

0Willcox Corvette

Ok.. Next...

Another thought.. go to your local flaps.. and order a 77-82 cylinder. if the threads for the lines are the same and the piston hole depth is the same you should be ok. If not then punt.. and refer to the last paragraph below.

Another thought.. If you have a wheel cylinder hone, why not order the rebuild kit vs. the cylinder.

I'd tell you to measure the depth of the piston and the size of the threads for the lines.... But it might be easier for you to just mail the thing to me. If I have your cylinder here, I can make sure what I send you is a match.

tdkask

Sadly, the local Advance and AutoZone both sell a remanufactured cheaper than a rebuild kit. I assume this suggests low quality parts... lol... but will get me fixed until I find the best long term solution.

I could pull the cylinder and measure everything if it'd help, but for the cost of two way shipping I can buy a 77-82 and see if it works. I think that's the best route anyway. There's one in stock in a store near me.

Can you confirm the front-front/rear-rear correlation? Thanks.

noonie

tdkask

First off, you don't have a corvette booster (not that it matters), so you have to check which of the two masters you possibly have.
Below is a pic of the two power masters.
Only difference is that the left one has a short holed piston (late) and the right one has a deep holed piston (early)(about 1-1/2" deep). Both are 1-1/8" bore and the port threads are the same.
You can carefully remove the mounting nuts and slide the master forward enough to see which one you have without removing any lines. In your application you may have to loosen some clamps for the brake lines to give enough movement for the master, careful not to kink the lines, slight bending is OK.
The best masters new are from NAPA these days. When you know which one, go in and prepay and they will have it in a day with no shipping charges. Around 50 bucks.
If deep is needed, order for a 74.
If shallow is needed order for a 78.

Not sure what you mean by that, but the front port is for the front brakes and the rear for the rear. This is opposite most cars. Rule of thumb is the larger reservoir is always for the fronts.