# Disc brake conversion, done but question on proportioning valve.



## Notagoat (9 mo ago)

Ok, new spindles and disks installed and new drums on rear, ( everything is new, even brake lines solid and flex) car is a 68 lemans, was drum/drum with manual brakes, I have purchased a disk conversion power booster and master cylinder set, comes with an adjustable proportioning valve, ( looks more like a tubing cutter lol) but there are no instructions in the kit, I will post link to kit below, wondering if it would be easier to buy a regular proportioning valve to replace the existing distribution block, as it looks like i have to install the new one in the middle of a line somewhere, any help greatly appreciated 

Darren


1964-1974 GM Disc Brake Booster Conversion Kit Combo


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## ponchonlefty (8 mo ago)

i would get a prop valve that's set up for disc front drum rear and call it a day.


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## Sick467 (Oct 29, 2019)

I have the same tubing cutter that came in your kit on a build of mine. I can't help you with installation, mine was too long ago, but adjusting it was easy. I have a gravel driveway and merely got moving enough to hit the brakes to see if the front or rear was locking up first... adjusted it accordingly to get both front and back to lock up at the same time... then took it to the pavement to find tune it. Very little fine tuning was needed. Probably took 15 minutes to adjust it. Haven't had to touch it in 10 years.


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## lust4speed (Jul 5, 2019)

A "proportioning valve" does look something like a tubing cutter and can be adjusted to balance front/rear brake balance. A "combination valve" is usually a block that has a combined function of splitting front/rear brake lines and also has a preset ratio for front/back pressures. The one-size-fits-all valve the aftermarket suppliers sell have to work on every installation from a pickup truck to a station wagon and everything in between (a factory combination valve had spring pressures adjusted for that specific vehicle). An adjustable valve allows you to increase or decrease pressure to the rear brakes to give the best stopping possible. It won't really matter until you are in a panic stop and then you might find yourself where it feels like you grabbed the emergency brake with the rear tires locked up and coming around to pass the front end. Or, like the problem I now have with the wagon's aftermarket system, the combination valve allows the front wheels to lock up while the rears are coasting along not really contributing much to stopping power.


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