Disc Brake Conversion

[72BLAZERDUDE]

I am trying to collect all of the parts to do a rear disc conversion on my 72 2wd Blazer and was wondering if I can use my current master cylinder and just need to get a new proportioning valve. If I get an adjustable one from someplace like Summit how do I set it. Or is there a stock one from a vehicle I can use.

[69k5]

you can use everythjing you have now as long as it is already disc. which being a 72 should be.

you might want to add the aftermarket prop valve later. just depends on if yours are locking up. just plum it and use pipe plugs on the original for the rear lines.

as for setting. trial and error till its where you like it.

69k5

[dinnut]

ive been told to use a corvette master cylinder and prop valve. some in the mid 70s had 4 wheel discs and they said they will work on our trucks
i dont know if i would try to run discs with drum equipment. discs take more juice to work and it wont operate like your wanting it to if you dont upgrade the stuff.
just my opinion

[Wootdog]

I have a corvette master cylinder with both of the resevoirs being the same size. Do I need a prop valve? Not to get on anyones post just wondering. Kerry

[Rooster's 67]

dinnut is correct, you really do want to use a master off of a 4 wheel disc vehicle, the key is not in the resivoir size but in the pistons and springs inside the master. The pistons need to be larger in dia. than the factory drum pistons due to the increased surface area of the piston in the calipers. how ever the drum brake master will give an easier to push pedal if you are running manual brakes. But the pedal(hence piston travel in the master) may not move enough fluid to effectively activate the brakes and leave a reserve pedal height. Try to find a 4 wheel disc master that came off of a vehicle that has close to the same surface area at the calipers,comparing your components to the donor M/C vehicles calipers. Ihave heard the early 70's corvette master will work . You will want to invest in a adjustable proportioning valve so you can adjust the front to rear brake bias, ideally you want the rears to lock up just before the front. that is when you know that you are getting all four corners to work at their best potential.

that would be my best $.02 without getting out the theory and design of braking systems book.

Have the kid at the parts store start pullin parts and check what will work.

[72BLAZERDUDE]

Does anyone know exactly the difference between a truck master cylinder with front disc brakes and a Corvette MC with 4 wheel disc. I think the truck MC actually has a bigger bore. Wouldnt that mean more pressure, much heavier vehicle.

[72BLAZERDUDE]

Checked it out and the piston size on a 76 Corvette Master Cyl is 1 inch. The piston on my Blazer is 1 1/8 inch. Even though there are drums on the back I would think GM handled the difference in pressure with the proportioning valve. I dont want to go to the Corvette Master Cyl. if the brand new one I have will work.Maybe Im all wet on this but brakes are not something I want to experiment with.

[dinnut]

http://67-72chevytrucks.com/vboard/s...orvette+master
gone bad 2 is gonna use the master cylinder for the mid seventies vet. talk to him. the adjustable prop valve is the way to go.
gone bad 2


http://67-72chevytrucks.com/vboard/s...orvette+master
check out that link. some links to a good brake parts company.