Now dave, I have a question for you, which is relevant to this thread... Lets say you had a later model dual style master cylinder, but no 'safety check valve' in the distribution block (Lets assume a Tee going to the front wheels, and the rears plumbed directly out of the master cylinder).. I'm not sure how they are setup 65's but do they have any check valve? Anyways, moot point, assuming the setup I just mentioned, if a line blew, would you still have the front or rear brakes? There is a tiny little divot for the rear brake fluid in the MC to be separated from the front brake fluid, but just wondering if there would be any resistance, and would they provide a little stopping? Once again, assuming new master cylinder (90's.. they aren't REALLY seperated, but a bit), and just a Tee going to the front, and rears directly from the master...

That is what I will be running, and if so, it's not really a pricey upgrade to do for disc OR drum (Depending on the master you pick), but I'm not sure if that actually will provide any safety if a line blows.. Although I know some people use Tee's..

 

Hey Johnny,

Are you talking about the newer ABS plastic master cylinder reservoirs?

Dave

 

Newer plastic, but no abs (I hope!) whats the difference? IS there any difference with the masters?

 

All the distribution block does is T the front lines anyway, so that makes no difference in the safety feature of a dual-bowl m/c. The safety comes in separating the front and rear lines. If you lose one, you still have the other, albiet with a low pedal.

Even with modern plastic-reservoir m/c's you still have separate systems, even though they use the same reservoir. The front and rear are still split hydraulically.

 

The old single bowl like in 65 and 6's are just very dangerous. Like Dave stated, if something pops, your SOL and will preform a crash dummy test. Thereseviors in new braking systems are a common fill, unlike the old ones that had a two different chambers. The fill line is above the chambers. Once the fluid enters the piston plunger area,it is seperated into two different citcuitsand are not connected (for fluid flow anyway). In the distribution block, their is a pressure differiential valve (plunger) that connects thetwo circuits but will not allow fluid to flow across unless the O-rings are bad and cracked (normally you will see a leak). This needs to becenteredafter the braking system isbled (the depressed area goes in the middle) no one does this these days. If equipped with a brake warning light (67 up I think), it will nowgooffand operate correctly if theirs a pressure failure in one on the circuits. In the block itself, their is aequalizer (proportioning valve) that will provide more pressure to the front when you hit the brakes real hard so that the rear don't lock up, and send you for a tail spin. Usually this is arestictor for the fluid (orifice) and the size will vary between the disc/drum, drum/drum, and disc/disc setups. A lot of race guys will use an adjustable one so that they can set the rear brakes for track use. These work great to fine tune the system. So when setting up your system, make sure you get the correct block also. Hope this helps.
On edit: the disc are much better that the old drums and are one, if not the best safety inprovments you can do. Also, loose that single bowl master, these are very dangerous. Around here I have had my brakes get VERY spongy going down the hills (heat). I would change it, but its on a concours vert.I keep the emergency brake in good order.

 

Just to clear this up, there is no proportioning valve in a distribution block. All a distribution block does is split the fluid and send it to different ends of the car, at the same time providing a pressure differential switch for the brake warning light.

A combo block has a built-in proportioning valve for the rear. This is why you can't simply put discs up front and leave the system as-is, you have to add a prop valve to the rear lines.

 

Yes, but the distribution block (At least for 67+ I believe) has that pressure differential valve in case of a leak. Is it safe to run without this (Just a tee to the front lines, and the rear coming straight off the master cylinder with an adjust. prop valve) as the master will still keep some fluid to the one that doesn't blow a line? Or do you need that pressure differential valve. The master cylinder doesn't really seperate the front/rear fluid.. So i'm wondering if a line blows, will there be any braking, or will the pedal just drop to the floor with no stopping to be had. My mechanic didn't like this idea for my car..

 

A dual bowl will let you at least have front or rear brakes.

 

Does anyone have a stock drawing of the power booster proportioning valve/distribution block for a 72 setup?

I just replaced my entire front braking system from drum to power assisted, I had ordered new front brake lines but tired of the wait and took the factory drum lines and fabricated them for the new valve (bent/cut/flaired). I am pretty sure of the setup but I had to cut the lines and install smaller fasteners then what was on the stock drum valve, from what I heard it was a mid model year change. It is a standard FOMOCO valve body.

thanks

 

There is no pressure differential valve. There's a pressure differential switch that turns on the brake warning light if there's a pressure difference between the two systems. Granted, it's fairly easy to notice a leak without that, seeing as the pedal is going to sink either way.