Master Cylinder for Disk/Disk Setup

[nuke82]

I'm looking for a cheap master cylinder to use on my 72 C-10 with disk/disk power brakes. If it matters the front calipers are stock and rear are 79 Lincoln Versailles (need to grind that Ford symbol off the calipers!).

I was looking at POL master cylinders but am hesitant because they are 1" bore.

https://www.performanceonline.com/Di...h-Performance/

I also understand a vette m/c can be used but was only able to find recommended part numbers for non powered systems.

Any recommendations?

[Jurassic-1]

I purchased one from Orileys Part # NMC1423 It is a 1972 Corvette with Power Brakes and it has a 1.125 bore size and runs about $35.00

[SierraMtns]

Here is the vette one I used. It works great with a 1" bore. I have a disc/drum set up. I would buy from these guys again.

http://www.piratejack.net/index.php?...product_id=200

Here is what your looking for.

http://www.piratejack.net/index.php?...product_id=447

Give them a call. Nice guys and they will help you figure out your set up.

[nuke82]

Both solutions look exactly like what I have been looking for, thanks! @Jurassic That should use the same rod right?

[SierraMtns]

Originally Posted by nuke82

That looks exactly like what I have been looking for, thanks! This should use the same rod right?

Are you running power right now?

[nuke82]

Yes, I'm running the stock power setup and the master cylinder has gone bad so I'm looking to replace it with something made for 4 wheel disc brakes.

[nuke82]

Ok, found the problem! At least they knew to circle it for me.

[Jurassic-1]

The rod length would depend on Power brakes being shallow and manual brakes usually are deeper. You can usually adjust the rod for fine tuning.

[RichardJ]

If the front disc brakes are stock and the Master/booster are stock and the front brakes do 60% - 70% of the vehicles braking, why would you want to screw that relationship up.
Replace the old bad MC with a new replacement.

Instead of changing everything, make the new rear disc fit what you know already works.

Disc brakes require more pressure than drum brakes, so if you have any problem it would be that the existing Combination Valve/proportioning valve may be reducing the pressure to the rear brakes too much. By that I mean, reducing the pressure to the rear in relation to the pressure going to the front.

If you have to do anything it would be that you replace the Combination Valve with an independent Metering Valve for the front brakes, plus an independent adjustable Proportioning Valve for the rear brakes.

[nuke82]

@RichardJ I have a bad master cylinder so if I have to do anything it's replace the master cylinder, lol.

Also, the stock master cylinder is not the proper one to run for four wheel disc brakes, it can get you by, as mine has, but the rear reservoir is too small. I was just having issues finding an inexpensive one, those Wilwood are too expensive for my little budget. This article spells it out nicely: http://www.motor.com/article.asp?article_ID=1969

[leftybass209]

You don't have to go straight to Wilwood for a quality mc, but bargain shopping for an inexpensive one is a great way to find a cheap quality mc.

POL has some good quality mc's that haven't leaked or caused me any trouble. The 1" bore isn't really going to be an issue. If you're still concerned it might be, give them a call and ask. Check with NAPA, as their customer service usually bests the other parts chains, and they have a higher chance of carrying some quality components.

It's best for your safety, and everyone else on the road to outlay a few $ more. I know everyone doesn't have deep pockets, and I sure don't, but safety items aren't the place to save a dollar.

[RichardJ]

Yes, I understood and mentioned that that you had stated your old MC was bad.

The reservoir size has nothing to do with the operation of the disc brake caliper.
Under normal operation, when you press on the brake pedal, there is very little fluid transfer from the MC to the caliper. Unlike drum brakes that have springs to pull the shoes back, away from the drum, caliper pistons and pads stay very close to the rotor.
Only over the course of thousands of miles and the life of the disc pads does the fluid slowly transfer from the MC to the caliper, behind the piston.

Shoe wear adjustment for drums as accomplished with springs and lever turning the star wheel. Pad wear adjustment for disc brakes is accomplished by slowly and permanently transferring fluid volume to the reservoir behind the caliper piston.

The reservoir is sized so that a couple of years down the road, you don't run out of fluid in the MC, before you wear the pads out.
If you never check the MC brake fluid level, then that could be important.

If you must choose a different MC, then choose one with the same bore size as the one you have now and the front brakes which do 70% of the braking will continue to function properly. Checking the booster pin length adjustment is always a good idea when replacing the MC, but imperative when choosing a nonstock MC.