Manual Brake Master With Disc/drum

[SierraMtns]

I'm working on putting on a manual master cylinder on my 67. I know that Wilwood makes one that bolts in. From my research I need a 15/16 bore. I have seen a couple posts that early 70s Corvette manual master will work with disc/drum combo.


Is there another OEM master that will? Has anyone used the Corvette master with this combo?


Happy Thanksgiving

[WIDESIDE72]

Ive had a few 71/72 trucks with manual brakes. I would think you could source one from a 71/72. When i added power brakes to them i never changed the mc.

[SierraMtns]

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[Tx Firefighter]

Why not just use a stock 71/72 truck master cylinder ? Cheap, available at any parts store, and it's factory GM engineered for disc/drum application right off the assembly line. Not that Wilwood don't make good stuff, but why reinvent the wheel and spend a pile of money ?

[cdowns]

that $15 solution is too easy not like ineventing the wheel

[SierraMtns]

Originally Posted by Tx Firefighter

Why not just use a stock 71/72 truck master cylinder ? Cheap, available at any parts store, and it's factory GM engineered for disc/drum application right off the assembly line. Not that Wilwood don't make good stuff, but why reinvent the wheel and spend a pile of money ?

Yeah I do like the idea of being able to get it from my local parts house.

Would I need to run a proportioning valve? Is there a difference between a early 70's Corvette master and 71/72 C10 master?

[RichardJ]

A proportioning valve has nothing to do with the master cylinder, manual or power. A proportioning valve is used with most disc/drum brake setups, because the same pressure applied to the disc calipers and to the rear drums will cause the rear drums will lock up long before the front calipers. The proportioning valve reduces the pressure to the rear proportionally, to how hard you are pushing on the brake pedal.

Manual master cylinders usually have deep hole for the adjustable brake rod that floats inside the MC bore. The brake rod is bolted to the brake pedal and adjusted for length.

Some master cylinders are now sold with a deep hole and an insert that allows a MC to be used for both manual or power.

Some nut cases use a power master with the shallow hole, on manual brake setups. Unless you drill the hole deeper, the rod can easily drop out and you have NO BRAKES.

[SierraMtns]

Originally Posted by RichardJ

A proportioning valve has nothing to do with the master cylinder, manual or power. A proportioning valve is used with most disc/drum brake setups, because the same pressure applied to the disc calipers and to the rear drums will cause the rear drums will lock up long before the front calipers. The proportioning valve reduces the pressure to the rear proportionally, to how hard you are pushing on the brake pedal.

Manual master cylinders usually have deep hole for the adjustable brake rod that floats inside the MC bore. The brake rod is bolted to the brake pedal and adjusted for length.

Some master cylinders are now sold with a deep hole and an insert that allows a MC to be used for both manual or power.

Some nut cases use a power master with the shallow hole, on manual brake setups. Unless you drill the hole deeper, the rod can easily drop out and you have NO BRAKES.

Cool thanks for the info on prop valves.

[SierraMtns]

So has anyone used a corvette master?

[hotrodder]

I used the corvette master cyl. on my 67. I have had no problems

[Tx Firefighter]

I guess I just don't get it. 70s Corvette were four wheel disc brake cars.

Trucks were disc/drum.

The 71-72 master cylinder bolts right to the firewall without mods. The master cylinder will come with a new pushrod that bolts directly to your pedal and it's exactly perfect for disc/drum truck applications. GM got it very right when they built these trucks with disc brakes. They had fantastic performance when kept in good order. Every parts store in America either has one on the shelf or can get it within a few hours for about 20 bucks.

Do what you want, but just remember, those GM engineers were smart and made good trucks. They knew what they were doing.

Personally, I've built a pile of trucks and always emulated GM engineering for the truck, or later model trucks in situations like brakes. I have even used the mid 80s aluminum truck master cylinders because they look prettier on a few of the builds.

[67swb72klb]

when I change to the disc in the front I also use 71-72 master cylinder with a adjustable prop. valve for the rear and even without a booster they still work fine

[SierraMtns]

Anyone else running this set up? Is there good adjustable prop valves out there other then Wilwood?

[WIDESIDE72]

If you are have front disc/ rear drum brakes, simply install a master cylinder and prop valve listed for a 71/72 truck. No point in reinventing the wheel.

[clemsonteg]

Where are you guys finding these things for $15? All my local stores want $30 for a reman and $70 for a new one

[WIDESIDE72]

I never mentioned price. Try Rockauto.com

[mechanicalman]

Originally Posted by Tx Firefighter

I guess I just don't get it. 70s Corvette were four wheel disc brake cars.

Trucks were disc/drum.

The 71-72 master cylinder bolts right to the firewall without mods. The master cylinder will come with a new pushrod that bolts directly to your pedal and it's exactly perfect for disc/drum truck applications. GM got it very right when they built these trucks with disc brakes. They had fantastic performance when kept in good order. Every parts store in America either has one on the shelf or can get it within a few hours for about 20 bucks.

Do what you want, but just remember, those GM engineers were smart and made good trucks. They knew what they were doing.

Personally, I've built a pile of trucks and always emulated GM engineering for the truck, or later model trucks in situations like brakes. I have even used the mid 80s aluminum truck master cylinders because they look prettier on a few of the builds.

X2 on the Corvette master, some people confuse a "corvette master" to a master cyl that has the same general outward appearance. Also, if you are using a 4W-DB master on a 2W-DB with rear drum brakes, wouldn't you need to add a "quick take-up" valve to overcome brake spring pressure and allow the rear drums to engage when they are supposed to? I thought rear drum master cylinders had one built in but I could be mistaken.

[RichardJ]

>> wouldn't you need to add a "quick take-up" valve to overcome brake spring pressure and<<

A Quick take-up valve is used in a master with a 3rd chamber and piston. That 3rd piston had a larger diameter than the primary and secondary pistons. Primary and secondary pistons are both the same diameter, what ever that diameter is.
The Quick take-up master was used with front disc brakes with low-drag calipers. The piston seals would roll up when the piston was pushed against the pad and rotor. When the hydraulic pressure was released, the seals would unroll and pull the piston back, much farther away from the pads than normal.
The purpose of the 3rd chamber was to return the caliper piston against the disc pad and then the MC primary piston would take over and do its job. The purpose of the take-up valve, was to prevent the 3rd chamber from interfering with the function of the primary piston.

[SierraMtns]

Originally Posted by RichardJ

>> wouldn't you need to add a "quick take-up" valve to overcome brake spring pressure and<<

A Quick take-up valve is used in a master with a 3rd chamber and piston. That 3rd piston had a larger diameter than the primary and secondary pistons. Primary and secondary pistons are both the same diameter, what ever that diameter is.
The Quick take-up master was used with front disc brakes with low-drag calipers. The piston seals would roll up when the piston was pushed against the pad and rotor. When the hydraulic pressure was released, the seals would unroll and pull the piston back, much farther away from the pads than normal.
The purpose of the 3rd chamber was to return the caliper piston against the disc pad and then the MC primary piston would take over and do its job. The purpose of the take-up valve, was to prevent the 3rd chamber from interfering with the function of the primary piston.

So would the stock OEM 71/72 have a Quick take-up valve built in?

[mechanicalman]

Originally Posted by RichardJ

>> wouldn't you need to add a "quick take-up" valve to overcome brake spring pressure and<<

A Quick take-up valve is used in a master with a 3rd chamber and piston. That 3rd piston had a larger diameter than the primary and secondary pistons. Primary and secondary pistons are both the same diameter, what ever that diameter is.
The Quick take-up master was used with front disc brakes with low-drag calipers. The piston seals would roll up when the piston was pushed against the pad and rotor. When the hydraulic pressure was released, the seals would unroll and pull the piston back, much farther away from the pads than normal.
The purpose of the 3rd chamber was to return the caliper piston against the disc pad and then the MC primary piston would take over and do its job. The purpose of the take-up valve, was to prevent the 3rd chamber from interfering with the function of the primary piston.

Oops I meant residual valve, screwed into the master cyl.

[SierraMtns]

Ok guys I have more details.

I called Riebes this morning to get a price on master cylinders. Here is the break down.

Remand $ 59 + $17 core.

Napa United (New) $81

Rabestos (New) $65 (Made in China)

Here is where I am a little confused. The parts guy said the bore on these Masters are 1.125". I thought they where 1" for disc/drum?

Does anyone have any sources to check what the bore should be?

Thanks

[leftybass209]

I am running non-power disc/drums on my truck. It's using a stock(ish) master cylinder from POL. From all the research I have done, the larger bore sizes aren't a concern for manual set-ups. It's more of a concern if you're using a smaller bore, or using a booster. The larger bore will be fine for the manual set-up. My question would be why are you looking for manual brakes? Is it money, or clutter? My truck brakes great, but it's fatiguing at a stop light holding the brake down after a while. I don't think living in a big city helps that though.

[RichardJ]

>> The parts guy said the bore on these Masters are 1.125". I thought they where 1" for disc/drum?<<

For the same application, 1.125" bore would be for use with a booster and 1" bore would be for non-power brake.

You say you've been told to use a MC for '70 Corvette, manual, disc/disc.

Ok, that's a master with a 1" bore, a deep hole for a floating brake rod and larger reservoir capacity disc brake/disc brake.

A MC for '70 Corvette with power brakes has a 1.125" bore, shallow hole for vacuum booster and larger reservoir capacity for disc brake/disc brake.

A MC for 1967 chevy pickup with manual brakes has a 1" bore, a deep hole for a floating brake rod and smaller reservoir capacity drum/drum brake.

The smaller reservoir just means you have to check and fill the brake fluid before the disc pads wear out.

[54blackhornet]

My 71 GMC has manual disc/drum , still has original master cyl and works great . When I first got it I was planning on upgrading to power brakes, but I think they work good as is....

[SierraMtns]

Update:

I have the manual master in for mock up. Working on where the prop valve will go. The new master didn't come with a push rod. I called around to other parts houses and their masters don't come with them either. So I am on the hunt for a push rod. Please let me know if you have one you don't need.

Old Set-up:





Bonus points for whoever can tell me what kind of master/booster this is. The PO put it in and I don't think it is a truck one because the resistor doesn't sit level.

New Set-up:






I do have a question about tubing size. Are there any issues with running 3/16" and 1/4" tube together in the brake system? The master is 1/4" and the Wilwood prop valve is 3/16".

Thanks for the help.