67 MC and dist. valve use on 66 drum nonpower

[Jonk67]

I searched and couldn't find the answer i was looking for. New guy in our club has a '66 (3wks. now) -manual 4wh. drum manual jelly jar. I am trying to help him replace the jelly jar with a dual bowl from my '67 4wh drum manual. He doesn't have the money to go disc or power yet so we just want to make it safer and freshen up the shoes, etc.

Is the pressure valve to shutoff the fluid in the event of a leak at the rear or L/R front lines built into the 67 dual bowl MC or built into the 67 dist. valve? I've read about using the '66 dist. valve but know it's just a ported block. I know the 67 has the light switch but can't seem to verify where the safety pressure valve is that is the whole point of doing the swap.

Would you suggest keeping the 66 valve and plugging the extra port as I've read or swapping in my '67 dist. valve also, which will require bending new front lines I believe. I know I'll need to bend lines from MC to valve either way, did this on my '67 no problem there.
Thanks, Jon

 

[B67FSTB]

Jon
To my knowledge , from 67 on they use the dual master cylinder and distributioblock because that system was much more safetier.. 2 seperate brake circuits.
So when converting from a 66 brake system to a 67 and up brake system , you need to change the mastercylinder AND the distribution block also.
When your car has drum up front and rear , the mastercylinder has 2 bowls that have the same volume/dimension bowls.
When your car has disk in front and drum in rear , the mastercylinder has 2 different seize of bowls.
Also a orig distribution block is different between drum/drum and disk/drum which has a built in pressure valve.
Look it up in any catalog and you wil find out the differences.

 

[Jonk67]

Good points, I didn't think about the disc/drum dist. valve having a prop. valve in it but it makes sense that it would cut down the amount going to the rear drum brakes. We won't have any confusion there since my valve is off a drum/drum car but it sounds like it just has the addtl. brake light switch he won't need so we could use his '66 valve and have fewer lines to redo. My MC is from drum/drum so the bowls are equal size unlike the disc(big)/drum(small) bowls.

This makes me think that it has to be the dual MC that has the valve in it to cut off the bowl that has a leak in it's system. Can anyone confirm that it is indeed the MC that has the shutoff valve in case of a leak in the system?

Jon

 

[B67FSTB]

Here are some pics to compare.In the disk-drum distribution block sits the pressure valve and front and rear circuits are independable./seperated.

 

[B67FSTB]

Jon , look close to the last pic , this is how you should do it.
Look close how the lines are routed.

 

[Jonk67]

Thanks for the pics as I didn't take any good ones when I disassembled my '67 and went back with a new/modded PDB system with adju. prop. valve.

So you are saying that only the disc/drum dist. valve has a pressure valve separating F/R in event of a leak?
So just the fact that there are 2 bowls in my '67 drum wouldn't be the safety feature over the single jelly jar and if I had a leak in my dual bowl drum system it would leak down anyway if the dist. valve allowed the front brakes bowl to bleed out of a leaky rear brake hose? That would be just as dangerous as a jelly jar system wouldn't it?

I looked at MU, NPD and CJ's catalogs online and they didn't have any desc. of the internal function of the dist. valve to state whether there was a low pressure cut off valve/ball of any sort. That's why I'm wondering if the dual bowl MC has the check ball in it?

 

[Jonk67]

Ok, I think I found a good explanation on another forum old post:

"On a car with all drum brakes a proportioning valve isn't used. This is only required on a disc brake system or a disc/drum system. It regulates the amount of hydraulic pressure that is applied to the front verses the rear. A combination valve has both valves incorporated into one unit.
On a dual braking system, there will be a small spool inside of the dist. valve that gets pushed to the side with the lesser pressure (because of a system leak) and the spool then blocks that end off. The spool at the same time pushes on a pin built into a nylon electrical switch that is screwed into the valve. When this happens it completes a ground circuit that lights a brake failure bulb in the instrument cluster.
On a car that has a front and rear drum sys. (manual or power), only a distribution valve is used or needed, as said. It is there to block off either the front or rear hydraulics if a leak is present (dual brake sys) and obviously, to provide a path for the brake fluid. It doesn't affect any pressure. The pressure differential needed between the front and rear, with drums, is controlled by the difference in the wheel cyl piston size and master cyl piston size as determined by the factory.Any 67 and up to about 1970 and maybe later, Ford vehicle with a drum front brake should have the same separate dist. valve and not a combination valve. There is a difference in the mentioned small nylon electrical switch that mounts to the valve on a 67 (67 only). It only has one electrical prong where from 68 and up it has two prongs. All you need to do is to swap the switch over to the one that you have on your 68, so that the connector will attach. This switch activates the brake failure light on the dash, again as mentioned."

I am trying to only focus on drum/drum system to avoid confusion with the disc/drum system but this quote shows the difference plainly to me.
End result to me is that using the dual bowl w/o the matched dist. valve (drum/drum) is no safer than the original '66 setup. You must use the '67-'70 dual bowl MC with the matched dist. valve with the light switch but don't have to use the switch. I'm guessing you can plug the light switch hole to clean it up on the '66.

When I tore down my '67 the brake light switch was not working (stuck on) which now make me think that the check ball to shut off rear/front brakes in event of a leak would not have worked in that case. The check ball moving is what shuts off the fluid and activates the light so if one didn't work the other probably wouldn't?
Jon

 

[B67FSTB]

Jon
My english sn't that good so
maybe this can help :http://www.thompdale.com/brakes/brakes.htm
The M/C with 2 bowls does seperate the fr/rr brake circuits.
The distributionblock Drum/Drum is just for the brake warning switch and to make a connection for the fr brakes.
The drum/drum distributionblock doesn't block of any lines that are leaking.
When fr or rr leaks , a plunger can move inside the distributionblock and the switch is pushed by the plunger.

 

[tarafied1]

Bruno,
I think the info Jon found is correct. The drum/drum valve doesn't change the pressure as it would in a disc/drum set-up but still acts as a safety to prevent pumping all the fluid out of the master cylinder, which was the whole point of a dual bowl MC. I believe it was government mandated. I also believe the function is in the valve not the MC. I've rebuild MC's before and don't recall any check valve in the 67 drum/drum MC.

 

[Jonk67]

Thanks for the input Craig. Thinking about it more the dual bowls are necessary for the separation of fluid in the MC otherwise the dist. vavle safety checkball would be defeated. I have rebuilt MC years ago and opened kits and TMK it is just seals/pistons/spring.

Now I have to look up how to get the '67 dist. valve apart to clean/free up the checkball.
Jon