Vacuum boosted MC for all drums

[Madgyver]

What master cylinder can I use for 4 wheel drums that is vacuum boosted?

PO had a drum/disc MC on it with no proportioning valve. It did alright till now. I need to replace the mc with something that will match.
I thinking a disc/disc mc will work and it will be ok for future upgrade to discs.

 

[stout22]

I'm running the disc/drum MC on my 75 stocker w/o the proportioning valve. I thought I might eventually put discs up front.

 

[Scoop]

Either the disk/drum or disk/disk will not have the check valves you need for drums. I run the stock MC with my 74 Ranger drum/drum setup using the WH bracket and booster. You can always pull the check valve when you convert to front disk.

 

[Madgyver]

Check valve?

Please tell me more about this check valve for drums.

 

[Scoop]

The stock MC has "residual" check valves under the brass fittings both front and rear. This keeps some pressure on the slave cylinders to keep them from backing off as quickly from the force of the shoe return springs. This can induce air into the system. Disks don't have return springs so it's not an issue with disks. However you don't want the check valve on disks as this will cause them to drag and wear out quicker.

To convert the MC to front disks simply remove the brass fitting for the front reservoir (actually the larger one on the rear of the MC!), use a #8 sheet metal screw and screw it into the check valve and pull hard! Reinstall the brass fitting and go from there.

I run the stock MC with the front check valve removed on my trail rig with the chevy disk conversion. Works fine.

 

[Madgyver]

Scoop, Thanks,
I learn something new everyday.
Is the check valve built in the MC?
Do I need the check valve on drums?