I am adding front disc brakes to my 1963 Volvo PV544 (a scaled down version of a 1947 Ford). I am replacing the stock Volvo frame mounted master cylinder with a Wilwood Tandem Master Cylinder with the remote reservoirs mounted high on the inner fender wells. I am using a Master Power Brakes Combination Valve (Combo proportioning valve, pressure differentail valve, and metering valve). The Combination Valve installation notes indicate a great amount of flexibility as to mounting the valve. However the notes state "The only requirement is that the valve be below the ports on the master cylinder. Mounting above the master cylinder will lead to air being trapped in the system". Mounting the combination valve below the frame mounted master cylinder will place the valve alarmingly and perhaps dangerously low. I am of the opinion that due to the fact that the reservoirs are mounted as the highest component of the entire braking system that the warning about mounting the combo valve below the master cylinder may not apply. I am interested in other experience or informed opinions as to the combo valve placement in this situation. Thanks.
The center bore of the combination valve should be below the center bore of the master cylinder. It can be as little below as the top of one is 1mm below the bottom of the other.
1962 Volvo PV544 mild custom (Koolest Kruiser award at Lead Ain't Dead - 2020). Master cylinder uses the stock Volvo linkage. Combination valve is on the wheel well and the filler jugs are on the steering mast. The filler jugs are higher than the combination valve. I did this installation in 2015, I don't recall any great difficulties - I believe that I cracked the lines at the combination valve to remove trapped air. This Volvo has driven to Dewey, OK and Mojave, CA. The only problem encountered is that the Wilwood master cylinder started leaking at about 6 years. I replaced it last year. A note on the pressure operated brake light switch. It takes some brake pedal pressure before the stop lights turn on (not a good thing in city traffic). I installed a mechanical brake light switch (on the brake pedal linkage) to give me a faster stop light illumination. And another note: The "Tradition Police" tend to delete anything that refers to a NON-American vehicle (even if the technology applies to traditional vehicles). That is why I seldom come here, I occasionally stop by to read up on the "Traditional Kustoms"and follow the adventures of friends that I made here. I sent you a PM in case this thread gets zapped. Russ
Best place to install these combo valves? Your s**** br*** bin IMO.... These are a fiction sold to us as something that's 'needed'. Let's look at that... The pressure differential valve is only there to activate a warning light if losing pressure in one side of the system. If you're not installing the light, it's not needed. Even if you think you need a light, trust me, you'll know when you've lost half the system without the light. The 'proportioning' function. The OEMs used literally dozens of versions of these, all tailored for the specific brakes used on their different cars. The aftermarket sells us a few 'generic' versions, non-adjustable, so no 'proportioning' going on here. If you actually need proportioning, installing a separate adjustable version is what you need. All you're trying to accomplish here is making sure the front brakes lock up before the rear brakes. If the rears lock first, the car will swap ends. The metering function. This is the only plausible part of these, although just how important it is is open to debate. Prior to split braking systems they weren't used (even on disc systems). Jaguar never used them at all, and they're not known for poor brakes.
I agree completely. In a previous thread I posted my experience with a Combination valve that was “spec’d” by a well known brake vendor for my four wheel disc system. After ****ing around with issues I finally threw it in the trash (literally) and installed an adjustable proportioning valve, problem solved.
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