65 disc brake master cyl fittings

[deaks]

They don't seem to do that size.

[ALLAN R]

Thanks Alan, was hoping to get one over here.

Chances are now that imperial thread fittings are not stocked in the UK. I wish these master cylinders would come with a set of fittings. They are all different and a bit of a PITA.

[deaks]

Thanks Alan, was hoping to get one over here.

[ALLAN R]

Fitting, 9/16-18 Male X 1/2-20 Female Brass Adapter (baer.com)

Will this do the trick?

[deaks]

Still got a weep on one of my master cyl fittings but can't find one on ebay. It's 9/16 UNF, The one i managed to get is bottoming out in the master. A lot of the ones in the states, use a 9/16 male to 1/2 female adaptor but I am struggling to find one on line. Ironically, i've got one on the MC of my Nova.

[deaks]

I used to adjust them until they were slightly binding, to get the crappy handbrake to pass an mot, then back them off after.

[ALLAN R]

After looking at some ford setups, the ones with the same prop valve as mine, are plumbed the same on the outputs, so I've swapped the two inputs and the brakes are a lot better but the travel is quite a lot, so I'm going to readjust the pushrod.

The large nut on the rear of the valve is the proportioning valve. The front brakes are plumbed from the outlets furthest from this big nut and the inlet for the front brakes should be the rear outlet from the master cylinder. The back brakes come from the remaining outlet below the prop valve and the rear inet should be the outlet from the front of the master cylinder.

If you have a lot of brake travel try adjusting the rear brakes, I just put a screw driver in the backing plate slot and wind the star nut out until it won't go any more but not wound hard against the drum.

[deaks]

After looking at some ford setups, the ones with the same prop valve as mine, are plumbed the same on the outputs, so I've swapped the two inputs and the brakes are a lot better but the travel is quite a lot, so I'm going to readjust the pushrod.

[deaks]

That looks like the one, I already have, how is yours plumbed.

[ALLAN R]

What valve do you use Alan.

It's this one

https://www.ebay.com.au/itm/231631393689

[deaks]

I read up on proportioning valves and other valves when I did my disc brake conversion. Simple proportioning valves fit in the rear brake line and don't have any lights etc so you still need a distribution block. Adjustable proportioning valves have an adjustable valve but they don't actually vary the pressure to the rear brakes but the pressure at which the proportioning begins. The percentage of pressure applied to the rear brakes is a function of the dimensions of a double piston in the proportioning valve itself. Initially under light braking pressure in the front and rear brake systems will be the same until the hydraulic pressure overcomes the spring holding the proportioning piston against its seat. After this the pressure in the rear brake system is controlled as a proportion of the front brake pressure. Thie point at which proportioning begins is called the split point. In adjustable valves the pressure of the spring on the proportioning piston is varied by turning the valve so it's actually the split point that is moved, or the point at which the valve begins to proportion the pressure.

The brass proportioning valves that double as a distribution block and contain the warning light also have a metering valve in them on the front brakes. The purpose of this valve is to hold off hydraulic pressure going to the front brakes until the back brakes are beginning to be applied. The theory being that disc brakes have no return springs whereas drum brakes have quite powerful return springs on the shoes, thus under light braking the drums will always be catching up with the discs, so the metering valve allows hydraulic pressure to go to the back brakes to start applying them before the metering valve opens to the discs. The metering valve opens at very low pressure before real braking begins.

The piston in the warning light has O ring seals on it to separate the front and back circuits and moves just enough to make the light come on. It doesn't generally block off the damaged circuit but on some designs it does.

I went for the valve with the metering function because I figured that car manufacturers wouldn't spend a cent more than they had to so if a metering valve wasn't necessary, they wouldn't have put it in.

What valve do you use Alan.

[deaks]

It's possible, but in the case of late 60's Fords and Mopars that distribution block with the shuttle switch does not shut off any fluid flow through it (it would be quite dangerous if it did).

I believe both of your pictures show distribution blocks but not proportioning valves. If you can be sure that the £100 combination valve is good for your set up then it seems a reasonable deal.

If you want to experiment to dial out any potential rear lock up then a pipe from the larger m/c bowl to a t piece to the fronts and a single line from the smaller bowl with an adjustable valve to the rear will work fine. If you need a dash warning light those valves that you illustrate are the way to go.

How is your car plumbed.

[richard]

Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around £100 new.

It's possible, but in the case of late 60's Fords and Mopars that distribution block with the shuttle switch does not shut off any fluid flow through it (it would be quite dangerous if it did).

I believe both of your pictures show distribution blocks but not proportioning valves. If you can be sure that the £100 combination valve is good for your set up then it seems a reasonable deal.

If you want to experiment to dial out any potential rear lock up then a pipe from the larger m/c bowl to a t piece to the fronts and a single line from the smaller bowl with an adjustable valve to the rear will work fine. If you need a dash warning light those valves that you illustrate are the way to go.

[ALLAN R]

Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around £100 new.

I read up on proportioning valves and other valves when I did my disc brake conversion. Simple proportioning valves fit in the rear brake line and don't have any lights etc so you still need a distribution block. Adjustable proportioning valves have an adjustable valve but they don't actually vary the pressure to the rear brakes but the pressure at which the proportioning begins. The percentage of pressure applied to the rear brakes is a function of the dimensions of a double piston in the proportioning valve itself. Initially under light braking pressure in the front and rear brake systems will be the same until the hydraulic pressure overcomes the spring holding the proportioning piston against its seat. After this the pressure in the rear brake system is controlled as a proportion of the front brake pressure. Thie point at which proportioning begins is called the split point. In adjustable valves the pressure of the spring on the proportioning piston is varied by turning the valve so it's actually the split point that is moved, or the point at which the valve begins to proportion the pressure.

The brass proportioning valves that double as a distribution block and contain the warning light also have a metering valve in them on the front brakes. The purpose of this valve is to hold off hydraulic pressure going to the front brakes until the back brakes are beginning to be applied. The theory being that disc brakes have no return springs whereas drum brakes have quite powerful return springs on the shoes, thus under light braking the drums will always be catching up with the discs, so the metering valve allows hydraulic pressure to go to the back brakes to start applying them before the metering valve opens to the discs. The metering valve opens at very low pressure before real braking begins.

The piston in the warning light has O ring seals on it to separate the front and back circuits and moves just enough to make the light come on. It doesn't generally block off the damaged circuit but on some designs it does.

I went for the valve with the metering function because I figured that car manufacturers wouldn't spend a cent more than they had to so if a metering valve wasn't necessary, they wouldn't have put it in.

[deaks]

Well, I've read that it blocks that part of the circuit off, so you don't lose all your brakes and the light flags the problem up. Surely, a distribution block wouldn't have a piston in there. The combination valve is around £100 new.