Joined: Tue Jun 03 2008, 06:57PM
Location: King of Prussia, Pa
Posts: 29
Has anyone converted their single master cylinder to a dual master cylinder with a propertioning valve and kept their existing drum brakes? I would love to convert to disc brakes, but it is not in the budget right now. So I was thinking of installing the dual m/c with prop valve, will any dual m/c that is made for drum brakes fit my car as long as it is for manual brakes? Any thoughts? My '66 Newport has manual brakes....Thanks!
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
Do not use a prop valve with drum brakes.
Order the MC for a Chrysler from 1967-71 with drum brakes. Plumb the front chamber to the rear brake line and the rear chamber to the front brakes. Re-use the original brass distribution block on the frame rail.
For the rear brakes, plumb the MC front reservoir using a short length of brake line to an "invert flare union" (Weatherhead 302X3 I think) to connect it to the original rear brake line which was removed from the distribution block.
For the front brake circuit, plug the original port from the MC with an "invert flare plug", If I recall correctly, the needed plug was a Weatherhead 131X4. They are available at NAPA and other parts stores. Then plumb rear reservoir to the port on the distribution block that used to be for the rear brakes, since it's the standard-size flare fitting.
When you upgrade to front discs later, the easiest thing is to install an aftermarket prop valve in the short line you made to connect to the rear brakes.
Also, when installing a new MC, make sure to check the adjustment of the pushrod where it engages the piston in the MC. (This might not be adjustable if you have manual brakes.)
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
My two cents... I know that a lot of people on here prefer proportioning valves, but personally, my preference is a combo valve. I used one from Master Power on mine, which is compatible with both discs and drums by doing a simple change. Benefit is the brake lines can be made at once, with no need to change them for the planned conversion.
One other thing. I did a lot of theoretical calculations, and found that using a 1/4" line from the splitter to the rear tee was preferable.
Joined: Sun Oct 09 2005, 05:02PM
Location: ALLEN PARK, MI.
Posts: 2007
Yea, I'm gonna have a SSBC dual master cylinder to.....ON MY WORK BENCH! Biggest piece of crap I put on my car! Sure, it stops ok, but the lid keeps seeping brake fluid all over the place! I tightened the fold-over spring with no help. My headers and firewall got a soaking!
Good thing I run SILICONE brake fluid! I bought the STRANGE plastic dual screw on cap style master cylinder. Just need to install it! Lighter than the SSBC IRON job, looks better, AND should be leak free! !thumb Tony P.
Yeah, don't use the old crappy DOT 3 fluid--it absorbs way too much water from the atmosphere and corrodes the innards of your system. I use Valvoline Synthetic Fluid, it bleeds the air bubbles out easier than silicone fluid, but doesn't absorb water - the best of both worlds! It is listed as DOT 3 / 4. <span class='smallblacktext'>[ Edited Sat Jul 18 2009, 10:24PM ]</span>
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
If your car is just for shows, and very occasional use, then silicone fluid is OK. for a daily driver, never, ever use it! If you MUST have a high quality fluid, use dot 5.2, which isnt silicone. Really though, Dot 3 or 4 is more than adequate.
Why, I hear you asking? Well, silicone fluid has two major drawbacks. One is that it aerates really easily, therefore adding air to your system. Second, the fact that it doesnt absorb water. This is KNOWN to cause little pockets of water in the pipes, which add to the air bubbles, cause localised corrosion, then a stress fracture in the pipe....
Joined: Sun Oct 09 2005, 05:02PM
Location: ALLEN PARK, MI.
Posts: 2007
Yea, I heard about this to (air) but my ride stops pretty good! As for the corrosion....be smart "like me" and use all stainless steel brake lines and your worries go "out dah door" you could say! Tony P.