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-   -   What type of Master Cylinder (http://www.hotrodders.com/forum/what-type-master-cylinder-78851.html)

49dream 01-15-2006 11:01 AM

What type of Master Cylinder
 
I have power drum brakes on all 4 wheels of my 1949 pickup.
with a double master cylinder.
I am putting the mustang IFS on with disc brakes on the front.
Do I need to change the master cylinder or can I use this one.
I was told that I need to have some type of valve to regulate the pressure.
Any help will be appreciated

johnnymopar 01-15-2006 11:07 AM

m/c's for a disc/drum combo have a dual reservoir where the disc reservoir is larger than the drum reservoir because the front calipers have a larger fluid capacity. the check valves you are talking about are usually 10# on the disc line and 2# on the rear lines. this will allow the rear brakes to activate before engaging the front brakes.

hope this helps.

JB

curtis73 01-15-2006 03:27 PM

Agreed, but I don't think you need the check valves to delay brake application. That's more of a safety thing designed to help the inexperienced masses control their cars.

I suggest this: Go to the parts counter and ask to look at their brake catalog(s). Look up the master cylinder that came with front disc brakes like the ones you have; like from an applicable year mustang. Use the catalog to identify the stroke and bore of the master cylinder's front plunger. Now, do the same research for the rear brakes. Then find a master cylinder that fits your booster and has a combination of the proper front/rear bore and stroke. What this does is properly provides the right base pressure to the wheels based on the size of the calipers, wheel cylinders and master cylinders.

It sounds complicated, but i think you'll find that almost all master cylinders from disc/drum cars are remarkably similar across the board; GM, Ford, Mopar, even some imports. If you have to find one that is just "close" you're still probably OK, but err on the side of more piston bore on the rear plunger.

Now, once you find that M/C you can install it, along with an inline variable proportioning valve on the rear brake line. They're under $40 from companies like Wilwood. Adjust it to wide-open, then take the truck out and apply the brakes until they lock up. Its almost guaranteed that the rears will lock up first. Keep adjusting the knob to limit rear pressure until you get lockup evenly at all four wheels.

302 Z28 01-15-2006 05:31 PM

[QUOTE=johnnymoparthe check valves you are talking about are usually 10# on the disc line and 2# on the rear lines. this will allow the rear brakes to activate before engaging the front brakes.

hope this helps.

JB[/QUOTE]

Not true, the check valves are used in systems where the master cylinder is mounted below the floor. This is to prevent brake fluid from flowing back to the master cylinder out of the calipers. A proportioning valve is what controls the rear to front brake differential.

You must use a master cylinder designed for disc brakes, they are different from drum brake master cylinders. The difference is in the bore diameter of the master cylinder.

Vince

Moon 01-17-2006 06:18 AM

Hi. A brake line with the disc brakes gets a 2# check, drum brakes get a 10# check. I think you only need these if the mc is lower than the calipers and wheel cyls. Check out this website, http://www.seattlestreetrods.com/index.htm, and click on the links by part. Virtually all the brake component links are there. Lots of good info in the sites.

Moon

49dream 01-17-2006 07:05 PM

Thanks everyone for the sites and information

Hotrodders rock on

Marcus :welcome:


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