[grivera]

I’m considering doing manual brakes on the 66 Lemans , which has aftermarket 4 wheel disc brakes. What is the recommended off the shelf master cylinder that looks period correct for and how does it get attached to the firewall. Currently there are 4 studs on the firewall. Do I just eliminate the two bottom studs or is there a bracket that goes there?

[b-man]

I have a ‘77 Malibu 15/16” bore master which was recommended by Torbin at KORE3 for my 4-wheel disc brakes (2008 Corvette Z06).

It was either that one or a Wilwood 7/8” bore master. I’m using a Wilwood adjustable proportioning valve. Yes you just use the two upper studs to mount it, just leave the two on the bottom alone.

https://forums.maxperformanceinc.com...6&postcount=12

[OG68]

Studs are from the pedal carrier. MC mounts to upper studs. Lower studs need nuts in addition to the MC hold down nuts to hold pedal carrier tight.

MC from a 68 shown. (67-72 Manual Drum Master Cylinder)

[grivera]

Excellent- thank you both

[Scarebird]

First we need to know the bore sizes of the calipers.

[grivera]

That I don’t know - the fronts look the same as the factory calipers on my 69 Lemans. I have to look at the rear - pic of backside here.

[grivera]

Assume fronts are D-52 calipers and rears are the late 70s Cadillac variety. Not sure of bore size.

[Scarebird]

Later calipers like b-man's have smaller pistons so he needs smaller bore master. You on the other hand have hydraulically what I have; I used a 1974-80 GMC C15 manual master which is 1". It is perfect as it matches what the factory did. You will need to mod the push rod to fit your stock pedal arm.

They also will make these masters long after we are all dead unlike the manual disc A/F units.




https://www.rockauto.com/en/catalog/...+cylinder,1836

[grivera]

Thanks for this info! So even with 4 wheel discs the chambers are different size? Also, the front ports serve rear brakes?

[Keith Seymore]

Originally Posted by Scarebird

Later calipers like b-man's have smaller pistons so he needs smaller bore master. You on the other hand have hydraulically what I have; I used a 1974-80 GMC C15 manual master which is 1". It is perfect as it matches what the factory did. You will need to mod the push rod to fit your stock pedal arm.

They also will make these masters long after we are all dead unlike the manual disc A/F units.




https://www.rockauto.com/en/catalog/...+cylinder,1836

For this set up: is some kind of retention required to keep the push rod from falling out of the master?

I would like to delete the power from my Chevelle (basically the same as a C10 pickup).

K

[Scarebird]

IIRC the pushrod has a little one-way lock clip on it, and the boot will keep the rod from falling out (usual GM solution). Longer boots for earlier masters may be available and fit, but I have not heard of a GM pickup ever having a rod fall out.

Originally Posted by grivera

Thanks for this info! So even with 4 wheel discs the chambers are different size? Also, the front ports serve rear brakes?

Correct on both counts.

[grivera]

Correct on both counts.[/QUOTE]

Do you have a pic of how you routed the tubing from proportioning valve to the MC?