Master Cylinder Modification for Front Disks...
 

Hi,

I just installed a front disk conversion kit on my 69 original 4 wheel drum car. I have been told that I can modify my existing factory master cylinder in order to achieve the correct front pressure and corresponding front/rear balance by removing a small restrictor, spring, and check ball inside the front brake line port on the master cylinder.

Does this sound correct?


Any help, additional clarification, and comments would be greatly appreciated.


Steve

I never heard of that. The KIT didn't come with a new master. Just go by a new one from auto parts store

I purchased my front conversion kit from SSBC, and since I didn't go with rear disc's, they gave me an adjustable proportioning valve to regulate the pressure to the rear brakes.

Sorry, not sure about tinkering with the master cylinder.

i been told that you cant run a dual drum master with disk/drum becaue the actual fluid champers are slightly different is size due to the disks requiring more fluid to operate correctly.

That's why I was told you can modify the Master as described in my original post. That's what the mod does is allow more fluid (hence pressure) to the disks.

I was just hoping someone else had heard of this before, because I agree with StoveBolts, I'm not crazy about messing around with the Master...

By accident, I just stumbled upon this. Check it out :-)

I would encourage you to read the whole page as it talks about the different master cylenders etc. It is very informative, one I'll bookmark for sure. :-)

Camaro Chassis - Suspension, Axle, Brakes, & Wheels


http://www.camaros.org/images/pages/...SM-422x359.jpg


On the new 1967 Camaro, this valve was initially used only on models with factory C60 air conditioning and it was described in the 1967 Chassis Service Manual in the following way:The November 1969 Chevrolet Service News adds the following (note that by 1970 the emphasis in the description was on front disc brakes, though the valve was also used on certain 67-69 drum brake cars):The implicit rationalization in the 1967 description was that the valve was needed to improve stopping due to higher front end weight resulting from the C60 air conditioning equipment. Restricting use to C60 is suspect logic; there were other options that added the same (or greater) front end weight. For example, in 1967, an otherwise optionless L6 with C60 would get it, while a RS/SS350 with smog, power brakes, and power steering (but no C60) would not get the valve, despite having a higher front-end weight.
Valve Usage
Usage of the valve was not consistent.

• 1967 Camaros that received the valve were: all models with C60 air conditioning, all SS396 models, and NOR-built Z28's (at least the later ones). However, the 1967 LOS Z28's did not get the valve.
• For 1968, only cars with 12-bolt axles received the valve. The C60 air conditioning option no longer caused use of the valve (though C60 cars could get the valve due to a 12-bolt axle). The one known exception is that NOR Z28's stopped using the valve midway through the 68 model and didn't begin again until mid-model year 1969.
• For 69, the valve was generally used on 12-bolt axle applications, except for JL8 equipped cars (which had disc brakes in the rear and didn't need the valve). As noted above, the 69 NOR Z28's did not use it until mid-year, in the late January / early February timeframe. Other exceptions in 69 include: some SS's and LM1's have been observed without the valve, and the valve has been observed on some drum brake 10-bolt axle cars.
• Note that usage of the valve on 67-69 Camaros was not apparently related to J52 disc brakes.

Opinions differ on whether the valve was effective at reducing stopping distance, but CRG has not seen any comparison braking data. If it was effective, why wasn't it used on all models, and why was the Z28 usage irregular?

i know all about that little valve. also in 68 it was placed onto the L30/M20 camaros the 327 camaros were not supposed to have it but the odd ball L30/M20 camaros came equipped with it. i did alot of diggin on that when i did background history on my 68 rs

Camaroboy,

Are you referring to the check ball/valve that I have been told to remove to make my drum-drum MC now work with my new front discs? My car is an original 327 car.

no im talking about the porportioning valve that stovebolts posted. more than likely your camaro doesnt have it. in the 68 the 327 camaros were supposed to be 10 bolt mono leaf rears while when optioned with the L30 327/275hp motor backed by a M20 4 speed then for some reason at chevy they added 12bolts and multileaf rears to these cars. then the that valve was added becuase of the 12 bolt. no other 327s were supposed to have it. and my 68 is a factory front disk car.