Hi guys, I am helping a friend get his 1965 back on the road after 12 years. He had the rear brakes converted to disc brakes over 20 years ago. I don't know whether this was a kit or a piecemeal conversion. Here is what I am seeing:

1. The brake pedal height is 6-3/4" from the carpet when the pedal is not applied. It is even with the unapplied clutch pedal, and it is difficult to transition from the gas to the brake. I am reading it should be at 4-3/4". Is 4-3/4" measurement with the brakes applied or not applied?

2. His brake system is a manual system. The pedal feel is very good. The pedal is solid when applied. I am a fairly strong man, but no matter how hard I push, the brakes will not lock up the tires. I am questioning whether it has the correct master cylinder. I believe there are 2 different ones: one with a 3/4" piston and another with 1" piston. I believe I should have the 3/4" piston. Is that correct? Is there any way I can check which one I have? Complicating matters is that the master cylinder looks to have been replaced as part of or after the conversion. Can anyone provide me with the correct MC part number?

3. I believe this may be an unrelated problem but possibly not. If I apply the brakes hard, the car pulls hard to the right. In order to keep it straight, I have to turn the steering wheel about a 1/8 turn to the left. I suspect this is a rear brake problem since I have to steer the car straight. In other words, holding the steering wheel in straight position still allows the car to go right. any thoughts?

Thanks for any help you can give me

 

First the 65 corvette had factory disc brakes unless it was a drum brake option car to save money. If the pedal is too high it could be in the wrong hole in the brake pedal arm. There is a manual and a power brake hole . Or it could have the wrong master cyl rod to the pedal. You have to check the stock length of these parts from a stock 65. To check the master cyl bore just unbolt and pull it out from the firewall. Use a caliper to check size. As far as the hard pedal and pulling, that could be bad hoses or a stuck caliper.

 

Take a picture of the master cylinder. Is it a stock 65 single? Is it a dual 67 style? If the car pulls upon braking, usually the opposite side is leaking fluid on to the brake disc. It could also be a clogged rubber brake line.

 

This was a rear drum brake car.

I assume I am to use the hole closest to the pivot with manual brakes?

Does anybody have this dimension?

thanks I will do that

 

It is definitely a dual. I will look at the lines. There were no obvious leaks. As far as pictures, the car is a good distance from me and my friend has health issues so I don't have easy access to the car. I only get to the car one day every couple of weeks. Good news is I got it running and drivable.

 

Just FYI, the car came from the factory with 4 wheel disc brakes or 4 wheel drums. There were no disc/drum cars. Only about 300 drum brake cars were built in 1965.

 

Yes, the hole closest to the pivot is for manual brakes.

 

That is interesting. I got that information from the current owner. I know he has the car from the late 70s-early 80's. Maybe I misinterpreted what he said. The question I have then is: is the 6-3/4" pedal height too high? I have two C3s neither of my brake pedals are that high. When test driving it, I hit the side of the brake pedal when going for the brake and assumed there was a problem.

Did the 65s come with a single or dual master cylinder or both? it does have a dual master cylinder on it. By its condition it looks to have been replaced recently, but the Owner tells me that car hasn't run in 12 years. It has not been inspected in 12 years

 

I don't know about the pedal height. That's really determined by the bracket itself, and perhaps it has been modified.

The non-power brakes in '65 came with a single-reservoir master cylinder. The power brake cars got a dual-reservoir MC. That particular dual-reservoir MC is quite unique and is very expensive.

 

If it's a dual master cylinder it may be a 1 inch or 1 1/8 inch. If it's 1 1/8 that would be part of the reason you can't lock em up. The factory single cylinder was 1inch. Correct 67 and later dual cylinders were also 1 inch. I have no idea what the bore is on factory 65/66 power brake dual cylinders. Factory non power master cylinders are also 1 inch bore.

And for sure check that the clevis is through the upper hole on the pedal shaft. Otherwise the rod will go into the master cylinder at a not good angle, if it even fits.

You can adjust the pedal height by threading the rod into the clevis deeper. You'll then need to get a thicker rubber pedal stop bumper to lower the pedal, or shave a bit of the bumper off to raise the pedal. The rod adjustment sets the point at which the brakes start to engage.

 

With regard to the car pulling off center when the brakes are applied , it could be tire pressure , or the tires or other suspension components and alignment .

 

If you haven't done this already, the first troubleshooting should be to get all 4 wheels off of the ground and spin them to see if one is dragging more than the others. The rear will have a bit more drag due to the drivetrain.
Then have a superior being (like my wife), slowly and lightly depress the brake pedal and hold it while you check all four for rotation again.
Then have that lovely person (she's looking over my shoulder) hit the brakes hard and hold them to see if all four wheels are locking up.
Then release the brake pedal and check to see if one is not releasing or releasing slower.
This should get you to the wheel with the problem unless the problem is in the parts design swapped into the car. Pictures of the calipers and master cylinder might help.

 

Sounds as though this car has had a checkered past of owners modifying what probably worked just in the first place...Until we figure out what Brakes are on it and what master Cylinder it has we will just guessing in the wind. If the master looks like a C3 master, then its a 67 or newer one. If so then it could be a PB or MB one. No mention of a Brake Booster. Since it sounds as though the rear brake conversion was done a wile back can we assume it is just stock Corvette parts and not aftermarket? If its Corvette Parts they change part numbers, but they all work the same 1965 to 1982 so we can count that out. Wile were at it maybe check to see what's up front.
By happenstance I changed the Master on my 66 manual brake car today and put the Pin in the wrong lower hole on the brake lever. It was so mechanically bound it the lever wouldn't even return. Putting it in the correct upper hole it was smooth as glass.
If I was to guess at what's wrong, I would say the brakes themselves are all stock despite what the stories say. And the problem is the Master and or Brake lever. Sounds as though your asking about the Brake lever height. When its all the way up it should be even with the Clutch lever providing it has one. But even if it is too high that's not going to affect its ability to stop. But only confirms that somebody has been in there messing with stuff.

 

It is a 67 or new MC I was hoping to get a part number and to know if the MC on it will work.

No Booster. They are manual brakes.
I finally got the car drivable and will bring it home to do a more thorough inspection. I was just trying to get a starting point.
After reading the above posts, I am inclined to believe you are correct.
I went down this rabbit hole because I was assuming that the brakes should have been similar to my C3s. Below is a sketch from the '73 AIM and it shows the height for manual brakes at 5.6" from the floor pan. I have 6-3/4" from the carpet. It is even with the clutch pedal though. Based on a 2020 post from Tom Dewitt, he had the same issues but modified the brake pedal to resolve. Based on all your posts and related issues, my guess is the brake pedal height is "normal" for a C2.