Disc Brakes on a '64

**Edward J.** · March 16, 2011, 07:43 PM

Re: Disc Brakes on a '64

Jim , It sounds to me like you hit it on the nose, the PSI would drop causing stopping power to feel a little different, I think I would take the master cylinder you have and rebuild it. they are pretty simple to do, as long as the bore is able to clean up with a hone you should be able to do in short time and the kits are cheap. If your not in your comfort zone there are drive line adveristers that will resleeve your old one.

If you own a shop manuel for your car, its all spelt out for in there. bore dia maybe different but all the same moving parts.

**Jim L.** · March 16, 2011, 08:00 PM

Re: Disc Brakes on a '64

Originally posted by James Baker (21868)

The car has power brakes and a non original 1" master cylinder (not a dual system as would be on a '65). I have a proper, rebuilt '64 master cylinder which is of course 7/8" bore and I would like to change to that but I am not sure what effect that will have on the system. Does anyone have experience with disc brakes and a 7/8" bore master cylinder? My guess is that it would put less pressure through the system & therefore not pose a problem- I just might lose a little in stopping distance.

Actually you'll experience the opposite effect by going to a master cylinder with a smaller bore. For a given pedal force, the line pressure will be greater. The pedal travel will also increase but you'll feel the brakes grabbing harder for the same pedal effort you are used to providing.

Jim

**Edward J.** · March 16, 2011, 08:06 PM

Re: Disc Brakes on a '64

Jim, Thanks for correcting me.

**Joe R.** · March 17, 2011, 12:15 PM

Re: Disc Brakes on a '64

Ed,

Stopping would be no problem with the 7/8" bore but the volume of fluid might cause a problem. That is bottoming out in the cylinder before the pressure was high enough to bring you to a safe stop. I doubt that this condition would exist but make sure you check out the travel of that piston or rod before exceeding the speed limit.

JR

**Joe L.** · March 17, 2011, 02:05 PM

Re: Disc Brakes on a '64

Originally posted by James Baker (21868)

I have a '64 L84 roadster, stock and original except that I put disc brakes on the car about 6 years ago (I just don't like drum brakes). Over a couple of years I bought suspension/brake parts until I had a complete disc brake/suspension set-up; took off my drum brakes and bagged them for storage. The car has power brakes and a non original 1" master cylinder (not a dual system as would be on a '65). This setup has worked well for the past 6 years but the MC is starting to leak. I have a proper, rebuilt '64 master cylinder which is of course 7/8" bore and I would like to change to that but I am not sure what effect that will have on the system. Does anyone have experience with disc brakes and a 7/8" bore master cylinder? My guess is that it would put less pressure through the system & therefore not pose a problem- I just might lose a little in stopping distance.

James------

I would not use a master cylinder designed for drum brakes with a disc brake system. Master cylinders used with drum brake systems have check valves; those used for most disc brake systems do not. I'd keep the correct master cylinder with the bagged drum brake parts for possible future re-installation and continue to use a 65-66 style disc brake master cylinder.

**James B.** · March 17, 2011, 05:55 PM

Re: Disc Brakes on a '64

Thank you both for your input. I could rebuild the 1" bore cylinder but I would like the originality of having the correct 7/8" unit- I know, that probably sounds silly given the disc brakes-but it would look correct to those peering into the engine compartment. Jim, thanks, sounds counter intuitive but I'll take your word for it.

**James B.** · March 17, 2011, 06:06 PM

Re: Disc Brakes on a '64

Joe, what is the purpose of the check valve? So apparently it is in the master cylinder. The 1" MC has been on the car for the ten years I've owned it. I have no idea what it is off of- and if it was for a disc or drum brake application. I will have to look around and try to find a disc brake MC that is not a dual circuit (don't want to cut and replace original brake lines); any ideas? Thanks for the warning and info.

**Gary C.** · March 17, 2011, 06:44 PM

Re: Disc Brakes on a '64

Gentlemen, caution using a '64 with Corvette dual master cylinder with power brake booster will not clear the hood. Ask me how I know. Gary....

**John H.** · March 17, 2011, 08:25 PM

Re: Disc Brakes on a '64

Originally posted by James Baker (21868)

what is the purpose of the check valve?

James -

All drum brake master cylinders (and the drum brake half of dual-reservoir disc/drum master cylinders) have internal residual pressure valves in the outlet for the drum system that maintain 10 psi hydraulic pressure in the drum system to hold the shoes off their stops, close to the drum friction surface, to minimize pedal travel on brake application.

If you use a drum brake master cylinder on a disc system, the 10 psi fluid pressure will cause the brakes to drag and fry the disc brake pads.

**Joe L.** · March 17, 2011, 11:08 PM

Re: Disc Brakes on a '64

Originally posted by John Hinckley (29964)

James -

All drum brake master cylinders (and the drum brake half of dual-reservoir disc/drum master cylinders) have internal residual pressure valves in the outlet for the drum system that maintain 10 psi hydraulic pressure in the drum system to hold the shoes off their stops, close to the drum friction surface, to minimize pedal travel on brake application.

If you use a drum brake master cylinder on a disc system, the 10 psi fluid pressure will cause the brakes to drag and fry the disc brake pads.

John-----

Yes, I had it backwards. I'll correct the post.

**Joe L.** · March 17, 2011, 11:13 PM

Re: Disc Brakes on a '64

Originally posted by James Baker (21868)

Joe, what is the purpose of the check valve? So apparently it is in the master cylinder. The 1" MC has been on the car for the ten years I've owned it. I have no idea what it is off of- and if it was for a disc or drum brake application. I will have to look around and try to find a disc brake MC that is not a dual circuit (don't want to cut and replace original brake lines); any ideas? Thanks for the warning and info.

James-----

See John's post and my correction regarding the check valve.

1965-66 Corvette master cylinders for non-power brake cars were single circuit. These master cylinders are also somewhat similar in appearance to the 64 master cylinder.

**Michael H.** · April 8, 2011, 10:50 PM

Re: Disc Brakes on a '64

if one wants to put power disc setup on the front of a 63/64, is there a recommended M/C? anything wrong with a 1-1/8 PDB MC from a 67-69 Camaro? Will this clear a 63 hood if used in conjunction with a 63 booster? Gary - I know it won't with a 64-67 booster. Have heard about that.

Thanks,

**Norris W.** · April 9, 2011, 05:10 AM

Re: Disc Brakes on a '64

Originally posted by Michael Holmans (22170)

if one wants to put power disc setup on the front of a 63/64, is there a recommended M/C? anything wrong with a 1-1/8 PDB MC from a 67-69 Camaro? Will this clear a 63 hood if used in conjunction with a 63 booster? Gary - I know it won't with a 64-67 booster. Have heard about that.

Thanks,

I don't know about hood clearance, but if you pull the lid off a Corvette M/C and compare it to a Camaro/Chevelle M/C you'll notice that the divider wall that seperates the two reservoirs is straight down on the Corvette unit, while on the other cars it's offset giving the front brakes reservoir more volume for the disc brakes front/drum brakes rear. I don't know if the JL8 Camaro has the Corvette style or the std type.

Disc Brakes on a '64

Disc Brakes on a '64

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