brakes lockup

[stock car driver]

You ever see someone go to the old "racing" synthetic fluid that would NOT mix with regular fluid. They would mix and it looked like burnt jello.

No, I have a fairly small group of racers that I travel with now and then and run special events and they arent into experimentation in the least.

Dot 4 is better for heat than 3 it has a higher boiling point so I suggest running dot 4.

[doitinthedirt2]

what proportioning valve are you using ? if it is one for rear drum brakes it will lock up your calipers. it needs to be one for disc brakes. they only have a 2 pound residual pressure compared to the 10 pounds that a drum brke prop valve applies. hope this helps. if it is an aftermarket vale it should have a big 2 for drum and a 4 for disc brake.

[jarvis]

not runnin a valve and I was told the calipers for the rear are off the front of a 84 grand prix he said it was the same set up he used and hasnt had any problems but heading to the track in a couple of hours see how it goes will let you know

[jarvis]

well the car was better tonite but it still wasnt rite was not burning hot dogs but the brakes were sticken Guys I have change everything what do I need to run

[gadirtracer]

What master cylinder are you using?

[jarvis]

Its off of a 84 grand prix i think. To the point of putting the drums back on as bad as i hate to. Tore the car apart today left rear was the worst the rotor was broke and they are off a corvette

[jarvis]

What is the best stock mount dual res master cylinder to get and I have a ford 9in with 4.75 bolt pat for rotors

[racerkrp1]

I use a mid 1960's corvette Master cylinder for manual 4 wheel disc. Works fine for me.. You can get them for about 30 bucks...

[gadirtracer]

Either your master cylinder push rod is not returning the piston all the way back or you have a master for rear drum brakes with a residual valve in the port. If you are still utilizing the factory brake lines, there maybe one on the frame rail somewhere "holding" 10 psi of brake pressure on the calipers. (As you said you removed the combination valve already.)
I would get a m.c. for something that came with 4 wheel disc brakes and carefully go over all lines under the car.
Only time a residual valve is needed is if the m.c. is lower than the calipers/wheel cylinders allowing the fluid to flow back to the m.c.
Let us know what you find.

[jarvis]

I ran all new lines from the master and I was told from the parts store the cylinder is from a 1968 truck and Im guessing it was disk all the way around since he said he is running the same set up but I did see my guy ran the lines on the master Front brake to front inlet on the master should the front be ran from the back side

[gadirtracer]

I ran all new lines from the master and I was told from the parts store the cylinder is from a 1968 truck and Im guessing it was disk all the way around since he said he is running the same set up but I did see my guy ran the lines on the master Front brake to front inlet on the master should the front be ran from the back side

I would think about all trucks in '68 had drums, front & rear. Look into the master ports and see if there is a brass insert in either of the ports, if there is one, get a new 4 wheel disk master cylinder.
If you are not wanting to purchase a new master cylinder yet, swap the front to the rear and rear to the front and see if the fronts lock up.
I'd put a new 260-4893 Wilwood Master Cylinder and be done with it.

[jarvis]

rules will not let me run a wilwood I am willing to buy a $ wheel disk brake one if someone tells me what I should buy earlier someone said mid 60s vette will it work or give me something you guys know for sure that works needs to be stock mount dual resivor and like I said the calipers and rotors are off the front of 84 grand prix shoul I change them to something differnt to

[brummi5050]

Im getting ready to convert to rear disc myself. I was looking in a brake parts book at later model camaro master cylinders. Same MC for drum or disc. So im guessing they dont have residual valves in the MC. I have a 79 Buick regal and I will be checking for the same. I dont want to change the MC if I dont have to. Has anybody just tee'ed off of the front brake side for all 4 wheels? Just a thought.

[keithbaker]

We use a single reservoir master cylinder off a 65 chevy truck. Only has one line that comes out of it and we split it to 4 wheels, works pretty good.

[cautrell05]

For god sakes people never use a single piston master cylinder for all 4 brakes. Thats just stupid no matter how you look at it.

There is no drum/ disk specific master cylinder. just different bore sizes. Find a book or somewhere that lists specs and bore sizes and pick from there. Your bore size is whats important. The original application dont mean squat.

Nick

[brummi5050]

For god sakes people never use a single piston master cylinder for all 4 brakes. Thats just stupid no matter how you look at it.

There is no drum/ disk specific master cylinder. just different bore sizes. Find a book or somewhere that lists specs and bore sizes and pick from there. Your bore size is whats important. The original application dont mean squat.

Nick

Wow thanks for the confidence! There are drum disc specific master cylinders according to the articles I have read. They have a residule valve built in the rear side, but thats probably stupid,too.LOL This is why people dont want to ask questions on sites. Didnt say im doing it, just asking if it will work. I thought if you use 1 for all, your braking would be even all the way around. My bad. Cant use racing MC or aftermarket proportioning valve either.

[jarvis]

Alright guys this is what it did bought a 1960s manual master with disk all the way around it ran new steel lines from it to all 3 corners with stingray rotors and calipers off of the front of 84 grand prix.Now does it mater were the lines conect to the master as in front to the front port on the master or vice versa

[cautrell05]

Wow thanks for the confidence! There are drum disc specific master cylinders according to the articles I have read. They have a residule valve built in the rear side, but thats probably stupid,too.LOL This is why people dont want to ask questions on sites. Didnt say im doing it, just asking if it will work. I thought if you use 1 for all, your braking would be even all the way around. My bad. Cant use racing MC or aftermarket proportioning valve either.

Not using a single master cylinder is about safety, plain and simple. You loose a hose with 1 single master cylinder and you loose all brakes. At least with a dual you will have some. Maybe not much but something at least.

In 18 years of turning wrenches professionally I have put alot pf mastercylinders on. Never once have I seen a built in valve on an older rear wheel drive application. Picking a master cylinder based off of application is not the best way to do it. It might get you close but your better off knowing exactly what your getting.
For example. 65 chevy c-10 is listed on rock auto as having a 1" or 1 1/8" master cylinder. -cast iron
75 camaro with power brakes 1 1/8 - cast iron
75 camaro with manual brakes 1" - cast iron
91 jeep wrangler 1" aluminum MC- looks just like the old cast iron ones
91 Dodge caravan 7/8 aluminum/plastic reservoir.

My car has the large GM calipers all the way around. A 1" mc with the brake pushrod moved up on the pedal. With the small metric calipers you may want to go with a 7/8 or 15/16. Too large of a MC will make it harder to push the pedal. Too small will take more pedal travel to apply.

Front or rear port. If both pistons are the same size then they both put out the same pressure. Dont let any one tell you other wise. The only difference on the cast style is one port has a large res and the other has a small one.

Nick

[brummi5050]

Not using a single master cylinder is about safety, plain and simple. You loose a hose with 1 single master cylinder and you loose all brakes. At least with a dual you will have some. Maybe not much but something at least.

In 18 years of turning wrenches professionally I have put alot pf mastercylinders on. Never once have I seen a built in valve on an older rear wheel drive application. Picking a master cylinder based off of application is not the best way to do it. It might get you close but your better off knowing exactly what your getting.
For example. 65 chevy c-10 is listed on rock auto as having a 1" or 1 1/8" master cylinder. -cast iron
75 camaro with power brakes 1 1/8 - cast iron
75 camaro with manual brakes 1" - cast iron
91 jeep wrangler 1" aluminum MC- looks just like the old cast iron ones
91 Dodge caravan 7/8 aluminum/plastic reservoir.

My car has the large GM calipers all the way around. A 1" mc with the brake pushrod moved up on the pedal. With the small metric calipers you may want to go with a 7/8 or 15/16. Too large of a MC will make it harder to push the pedal. Too small will take more pedal travel to apply.

Front or rear port. If both pistons are the same size then they both put out the same pressure. Dont let any one tell you other wise. The only difference on the cast style is one port has a large res and the other has a small one.

Nick

Now were talking. Thank you this really helps. I read the brakeman article and missed the part On most American cars and trucks up to the mid 1960's had valves in the MC. My stocker is either 7/8 or 15/16" piston which should be fine for my application once I get rid of the combo valve. Thanks again! Mark

[dirty white boy]

Not using a single master cylinder is about safety, plain and simple. You loose a hose with 1 single master cylinder and you loose all brakes. At least with a dual you will have some. Maybe not much but something at least.

In 18 years of turning wrenches professionally I have put alot pf mastercylinders on. Never once have I seen a built in valve on an older rear wheel drive application. Picking a master cylinder based off of application is not the best way to do it. It might get you close but your better off knowing exactly what your getting.
For example. 65 chevy c-10 is listed on rock auto as having a 1" or 1 1/8" master cylinder. -cast iron
75 camaro with power brakes 1 1/8 - cast iron
75 camaro with manual brakes 1" - cast iron
91 jeep wrangler 1" aluminum MC- looks just like the old cast iron ones
91 Dodge caravan 7/8 aluminum/plastic reservoir.

My car has the large GM calipers all the way around. A 1" mc with the brake pushrod moved up on the pedal. With the small metric calipers you may want to go with a 7/8 or 15/16. Too large of a MC will make it harder to push the pedal. Too small will take more pedal travel to apply.

Front or rear port. If both pistons are the same size then they both put out the same pressure. Dont let any one tell you other wise. The only difference on the cast style is one port has a large res and the other has a small one.

Nick

great post!