Corvette M/C for disc/drum application

I have a '75 vette master cylinder that is listed for disc/disc but I want to use it for disc/drum on my truck. Can I hook it up with my wilwood prop valve and simply turn the valve down to make up for the pressure difference?

EDIT: I'm also going to stick a 10# residual valve in the rear.

 

I think the main difference you'll see between disk and drum master cylinders is the size of the reservoir. Disc brakes store more fluid in the calipers as the pads wear, so they need larger reservoir so it won't run dry. Drums don't have this problem.

Disk/drum masters have one large and one small reservoir, while disk/disk have two large reservoirs.

Should not make any difference.

 

Good deal! Thanks squirrel.

 

I think it might work, but their may be a volume issue. I think the vette m/c has equal reservoirs, whereas the std disc/drum m/c has diffferent capacities for each

Edit: squirrel beat me 2 it

 

There needs to be a residual pressure valve so the shoes work properly. They sell them as inline units. Its a need to have item. They sell them in different pressures. I would start at willwoods website.

 

Starting around 1968, pretty much all cars had a "combination valve" that had the proportioning valve and residual pressure valves in it, as well as the idiot light switch. If you use one of these that's made for a car with similar brakes and weight as your car, it should do the job.

 

Needs to have 10 psi minumum residual pressure. Any chev pass. car with disc/drum should work.

 

I have the same set up on a '29 Chevy and have been fighting it for 3 weeks now. Bled it to death, bought another new Vette 1" bore Disc/disk MC like the first one still the front disc's work fine, back Ford 8" drums on rear barely stop the wheels from turning. I am yanking the Willwood prop. valve off the rear as I have never seen any diff. full on or full off. Next step for me is adding a combination valve in hopes I can get this damn thing over with.

 

Let us know if & how you fix it.

 

Be careful which Chev. m/cyl. you choose, some don't have rpv's because the wheel cylinders in the OEM application had cup expanders in them which negated the need for the rpv. in the m/cyl. Use the Corvette master and install an inline rpv and you will be fine. By the way, the 10 psi rpv has nothing to do with the brake shoes, it prevents air from being drawn into the wheel cylinders when you get off the brakes. The wheel cylinders use chevron type seals which only seal when pressure is applied to the back side. Releasing the brakes eliminates the pressure which would allow air to enter the system. RPV or cup expanders in conjunction with the compensating port in the m/cyl. prevent that from happening. Also, make sure you have the m/cyl. plumbed correctly.

 

Thanks for the info. Do I need a metering valve in my front circuit too? It seems like everywhere I look people are saying different things. Also, everyone is getting the terms confused with each other. For example, when I type in "metering valve" into Google it shows me tons of links about proportioning valves...

 

Not to steel Matts thread here but to get to the answers, I have the proper RPV inline to both front and rear as I have done for years.
The ECI web site says that the RPV's even in the M/C are not accumulative so having them in the M/C & inline shouldn't matter, my M/C is void of the RPV though.
When you say "plumbed properly" I have the port closest to the mounting flange going to rear.
I know the Vette M/C is a 1" bore and not a stepped bore so explain why it matters which goes to front or rear OTHER than reservoir size. Thanks

 

Then I see diagrams like this from CPP that doesn't have residual valves or metering valves in the setup.

 

They maybe assuming it is firewall mounted, high above the wheel cyl.?

 

Yeah that's the way mine will be. Mounted on the firewall. But according to ECI's website you should still run a 10# valve to the rear regardless of where the m/c is, because it prevents air from being ingested at the wheel cylinders when you let off the pedal. The 2# is only required in the front when the m/c is below the calipers.

Now I have another question. Is it important where the residual pressure valve is installed in the rear circuit? Can it be installed after the proportioning valve?

 

I think I got this figured out, but could someone just answer this for me: Does it matter if the 10# rpv is mounted before or after the proportioning valve?

Various sources have stressed one way or the other, which makes it more confusing to know which is the right way.

Thanks.

 

It's best to mount the residual(s) close to the master, and before the prop valve.

 

wow great info guys! ive been wanting to relocate my m.c. to the fire wall of my 49 shoebox. and get rid of the frame mount one! i have done a disk brake conversion and dont like the set up on the frame!

 

Some disc/drum masters have the rpv's incorporated into the outlet port of the master for the rear brakes.

 

http://www.mpbrakes.com/technical-support/reference.cfm

awesome reference and FAQ section -