Can anyone tell me what this proportion valve came from? It's from a front disc rear drum set up. I bought a scarebird front disc bracket kit for my Riv and the gentleman was nice enough to throw this in too. Thanks!
OK, so that is probably for a 1970 or earlier car. Combination valves started in 1971 I believe. What car? Who knows? Any numbers on it?
I di know it was on a 1970 Electra convertible along with the brackets I bought. The only numbers on it are in the pic. Side question for you Larry can I still use my stick booster that's in my Riv now or do I need to change it? My 69 Riv has power brakes but drums all around. I'm switching to disc front drum rear that's why I asked if he had the proportioning valve also so he threw it in the box of stuff for me.
I'm not sure if the boosters are the same, they may be. Front disc brake systems use a hold off valve. On my 70 and earlier cars, the hold off valve was mounted under the master cylinder, and was separate from the proportioning valve, and warning switch mounted on the frame. Starting in 1971, all three functions were combined in a combination valve mounted on the frame. I don't know what you have there.
I tried pushing it in with a screwdriver but no go. It looks like it has a knurled lip on it as well as a smaller pin in the center as if it was to be pulled or unscrewed outward like a larger bleeder screw?
Why does the Holdoff valve need to be „hold-in“ when bleeding brakes? Sry no intention to disturb thread, just noted that on Larry’s diagram and made me curious. Patrick
to open the outlets to the front brakes without pressure in the system in normal working condition (brake pressure) the valve is designed to do this: "The valve serves to equalize front and rear braking by delaying the application of the front discs until the rear shoes have had time to close the gap of 1/16th of an inch or so and contact the drums" otherwise your rear drums will lock up before applying pressure to the front discs
X2, Disc Brakes are inherently instant acting, Drum brakes operate with clearance and have to overcome spring tension to apply and self energize.
Larry, upon looking at your diagram more closely that is exactly the same valve as what I have. Once I looked at it a bit better I realized that the knurled lip is what the rubber cap grabs onto and the pin in the center is what you depress to bleed the valve/system. I took a small nail and tried to push that pin inward with no luck. Maybe it is seized from not being used for a long time or does it have to be pressurized by fluid?
My thoughts on the subject. I ALWAYS use a metering/hold off valve. Cheaper & MUCH easier install. One line in. two lines out. You can even mount it where the original splitter is on the frame so there are now two less lines that need to be made up. The main thing about those proportioning valves is that the RED LIGHT on the dash comes on to alert the driver of a problem.. May be nec. for the average consumer BUT not your normal gear head. When the brake pedal goes lower than we are accustomed to most times we will investigate. Then again WHO goes to the trouble of wiring it up to our parking brake light switch. In my shop I NEVER pushed down on that pin while bleeding brakes. I centered it by pushing on the brake pedal until you felt a "pop". Tightened up the bleeder & the valve was now centered & no more brake light on the dash.
Being it looks like it is used, unsealed and it probably had DOT3 in it, it has most likely absorbed moisture and rusted itself into a block scrap. They aren't too expensive. Buy a new one and life will be much easier. Todd at Stage 1 Restoration sells the proper one with the correct wiring connection for our cars for $79 and anything else you might need to finish the project. https://www.stage1restoration.com/product/distribution-block-1971-72/
Our price: $7.99 Performance Online's new Combination and Proportioning Valve Bleed Tool is designed to replace the warning light switch (white plug) on the proportioning valve during the brake bleeding process. After the bleeding process is finished, simply remove our PvBT Tool and reinstall the warning light switch. This item makes bleeding your brake system much easier. Works with all popular non adjustable GM style combination valves. Will also work on AC Delco 172-1353, 172-1371 and many other GM proportioning-combination valves. Tool is designed to lock the low pressure shut valve to allow fast and easy brake system bleeding. No need to constantly remove low pressure switch and center the low pressure valve during the brake bleeding process! Kit includes: 1/2"-20 thread pitch Delrin Construction
Do you mean don't bother using it? Can you elaborate a bit? Maybe pics of your master cylinder and reservoir set up or anything else that could be of some assistance. Cheers
