Correct Proportioning Valve?

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SteveM

SteveM

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The attached photo is similar the valve that came off my car, is it the correct one I need for my application? I have front disc (73+) and rear drum. In doing some research, this valve has an ID # PVM70. All replacement versions look blocky and nothing like it and I am having a hard time finding any info on the valve itself. Are adjustable valves worth the investment?

I am thinking of all disc one day, but not today. I am still fixing things the previous owner had done to my 67 cuda and I want to make sure I am making sound upgrades. Thanks for any ideas.
 

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A body disc brake proportioning valves look like this, pretty much from the years 1972 - 1976.
In 76 they did use a cast iron valve, so maybe that might be what you have. Dunno? I don't have a picture of that type of valve.
Hope this helps.
 

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I have never seen one that looks like post #1, so might have come from an Aspen/Volare or such. It also appears to have 2 electrical connectors. A-body ones only had one connector for the "pressure imbalance" switch. An adjustable prop valve is good, but only if you adjust it. Ideally, skid in a wet parking lot, adjusting until the fronts skid just before the rears do. Pickups are where the ratio needs tweaking with load. Some have an adjustable prop valve with an arm that senses how much the bed is loaded. Not sure how well that works or if reliable.
 
I have one of each cast iron and brass block here. Donors were a 73 Valiant and a 75 Valiant. Both lbp disc brakes.
What might look like a second switch attachment on the cast iron one is actually a centering or reset stem. I never knew what the build designation or differences were.
 
RedFish said:
I have one of each cast iron and brass block here. Donors were a 73 Valiant and a 75 Valiant. Both lbp disc brakes.
Click to expand...

"LPB disc brakes"? It seems like my block will work on my disc/drum setup, is that what you are saying? Definitely do want to drop the money unless I need to.
 
Id go with a Summit adj prop valve. Easy to use, easy to adjust. There are many variables with brakes, tire size, type, weight. you cant assume that a stock piece will work with even fatter tires. youll lose your brake lamp warning light but hey, you may not even have seat belts!
 
SteveM said:
"LPB disc brakes"? It seems like my block will work on my disc/drum setup, is that what you are saying? Definitely do want to drop the money unless I need to.
Click to expand...

Used proportion valves are like used master cylinders ( even more so with cast iron body ) in that while they lay open to atmosphere with residual brake fluid inside... Moisture is drawn in and rust grows.
If my memory serves, someone did find a online vendor offering "rebuild" parts or kits. A factory service manual states that these valves "are not serviceable".
If I ever had put the disc brake setup under my car, I would have went ahead and purchased a new proportion valve, and probably the adjustable type.
 
Yeah the brake fluid looked like an Irish Red on tap. New p-valve... No sense skimping on brakes. I saw some adjustable valves on jegs with two wires for a back up lamp. Any ideas on how to wire that with the single wire lead I have? Thanks everyone for the replies!
 
A 2 post brake warning switch... I'm fairly certain that switch was used so the valve could be mounted anywhere including on plastic or other surface not conducive to chassis ground.
OEM wire to either switch terminal. Other terminal will get a jumper wire to chassis ground.
 
Yes, for a brake warning switch... not back up lights.... (Hooked to the back-up lights might be interesting though... then when you back up in the dark and and hit something, you could just put on the brakes hard and see what you just hit. LOL)
 
Yes brake lights, not back up lamp. :violent1: Thanks for the inputs. My engine is in pieces and I am cleaning up my wiring harness. I will make sure I put it together correctly!
 
Your part looks exactly like the B-body one according to my 1974 shop manual. The E-body one is very similar as well. hemi71x showed you the one for the A-body.

From the manual: "The metering valve holds off hydraulic pressure to the front disc brakes in the 3 to 135 psi range to allow the rear drum brake shoes to overcome the return springs and begin to contact the drums. This feature helps prevent locking the front brakes on icy surfaces under light braking conditions. The metering valve has no effect on front brake pressure during hard stops." Also, "A slight 'bump' can be felt by the foot as the brake pedal is stroked. This bump will occur after the pedal has been stroked about 1 inch." (If the bump is not felt, the valve is faulty.)

Otherwise as far as I can tell this valve has the same functionality as the A-body valve. According to the testing procedure, the rear pressure reduction is in the same range for both. It looks like the only difference is the metering function.
 
zombywoof said:
i have one just like that one.... its a kelsey hayes valve i poached off a 74 charger. from what i have read they are rebuildable. here is a link with more info

https://www.musclecarresearch.com/kh-iron-combo-kit-1
Click to expand...


I have one just like yours. Removed from a 1973 Plymouth Satellite with disc brakes. Kelsey Hayes #89410. I've been told that this pv is from an E Body when I had it displayed at a swap meet???

IMG_5351.jpg
 
I ran 275/60-15s out back, with a gutted Pvalve,and 7/8 W-cylinders and 10 x 2s . No premature lock up with that. When I fit the 295s on there I went to 15/16.
235/60-14s on the front with both, and KHers.. I'm running less than 52% front weight bias.
 
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