So after much opinion on disc vs drum, I decided I want to keep my car correct with drums. However, I don't want to run the single master cylinder after reading the horror stories of a single pot system losing a line and having no brakes. I know Walton makes a kit for running a mustang disc/drum master for discs. Could I buy the same year master for drums and run it on my car with drums all around? Posted using the Full Custom H.A.M.B. App!
Only if you use the correct fluid. Technically, yes. As long as you can get it attached, and the pushrod in properly. You might need to alter the pushrod/and/or add an adjuster.
That's fine with me. I guess my concern is will the MC have the correct bore and stroke to operate the drums on my Chevy Posted using the Full Custom H.A.M.B. App!
You'll be okay with a Mustang master on that car. But you'll have to go with a drum/drum master. Napa or Rock Auto has them. Is your pedal under the floor using the OG mounting? If so you'll have to dig up or make a bracket to hold the master to the frame and do something about a clevis to work the rod. Also look at GM product masters like a '68 Chevelle drum/drum master. The push rod may work out better with what you have on your car.
The drums won't now what kind of master cylinder your using if you don't tell them! You will be fine. HRP
Like this thread, a little hummer for a change! One thing to keep in mind is the location of the MC and if it has internal residual valves or not. If not you may have to add them. It will depend on how the brake behave once the MC is installed. The brake shoe return springs can pull the shoes back to far forcing brake fluid back into the MC. When this occurs it takes extra brake travel to push the fluid back into the wheel cylinders to expand the brake shoe again. Residual valves maintain enough pressure in the lines to keep the shoe return springs from pulling them all the way back. Some MC have them built in and with some systems you need to add them.
To the original question, most common Master Cylinders are in the 7/8 to 1 1/4 range with 1 inch being common. What was the diameter of the original MC, if you want an exact match, use that diameter on the dual MC?. However, slight deviation up or down from that diameter is not going to make a lot of difference. A little larger dia will give you decreased pressure with a little less travel and more fluid volume, a little smaller dia will give you more pressure with a little increase in travel and less fluid volume.
Yep, spelling kills me every time! Guess what is not one of my strong suits. I'm sure you will see a lot more of it, spell check can only do so much! And I also worked as a technical writer, but had good prof readers saving my a** most of the time. Edit: Do I get extra credit for being old?
The popular late'60s/early '70s Mustang master cylinder has a very common 1" bore and will work with most car and light truck brake systems. You just have to make sure the pedal can fully stroke the master, something that needs to be checked on any custom system. You can use a Mustang drum/drum master, but using a late '60s-'80s disc/drum master on a drum/drum system is a better idea for several reasons; they are more plentiful than drum/drum masters, the larger front system fluid chamber prevents incorrect plumbing, and you're all set for a future front disc conversion. Residual valves- still a lot of confusion/misinformation on these simple little guys. Their purpose is to prevent air from entering the drum brake wheel cylinders during fast brake release, period. They can not/do not keep the shoes from their anchors, as some aftermarket brake suppliers even state. No way can a 10-20 lb. check valve overcome the very powerful shoe return springs, whose sole purpose is to fully return the shoes to their anchors. Residuals were used on all drum brakes up to about the mid '70s, when front discs and internal wheel cylinder improvements made them obsolete. They can benefit even late model drums with a slightly better pedal, and are used on my custom builds. They may not be installed in the new/rebuilt master you use, even if they were initially from the factory, so inline 10 lb valves may have to be used. The 2 lb residual is strictly an aftermarket item and should only be used with discs when the master is below floor mounted, to prevent possible fluid syphoning.
"Residual valves- still a lot of confusion/misinformation on these simple little guys. Their purpose is to prevent air from entering the drum brake wheel cylinders during fast brake release, period." Good point V8 Bob. Just an example of how you can repeat vendor information without thinking it through. I have used residual valves on all of my builds and really should have known this one!
I just bought everything needed for this conversion from ECI. . .except i added a disc brake kit as well. ECI has been building this brake kit since 1981 so I ***ume they have it figured out by now. Ralph at ECI mentioned that I could run drum/drum or disc/drum with the mustang master cylinder that he is shipping my way. I believe he suggested a 10PSI residual valve if running drums up front, 2PSI if I mount the disc kit. I'll be parting with my 54 backing plates and hardware as soon as I get everything tested. If you want more info on the parts in the kit, shoot me a PM, they should arrive early next week.
I think you're right. I get eci and Walton confused on the parts they offer. Posted using the Full Custom H.A.M.B. App!
Nice info Curbfeeler. . .I'd feel bad about spending the coin on the ECI kit if I could weld worth a darn. Wish I'd have seen that PDF sooner because I'd have sent the drawings to the fab shop and saved $100!
What PDF? I work at a precision sheet metal and machining company. I can fab my own if somebody has prints Posted using the Full Custom H.A.M.B. App!
http://www.hemmings.com/hmn/stories/2010/05/01/hmn_feature29.html Cool link with a great list Posted using the Full Custom H.A.M.B. App!
1949 and up Chevrolet single-circuit master cylinders can be converted to a non-power, 1-inch bore, dual-circuit master cylinder using a replacement unit for these vehicles: • 1967-'68 Chevy II • 1967-'69 Camaro, Corvair • 1967-'72 Chevelle, El Camino • 1969-'74 Nova • 1970-'72 Monte Carlo • 1971-'72 GMC Sprint, Pontiac Ventura II • 1971-'74 Pontiac Ventura • 1973-'74 Buick Apollo, Olds Omega This is a manual master cylinder with a deep pushrod hole. Posted using the Full Custom H.A.M.B. App!
The Jalopy Journal
