Front Disc Conversion - prop valve/distribution block/residual pressure valve

[andrewwoz]

In the process of getting my 69 Super Bee back together and decided to upgrade the front brakes. Engine is currently out so trying to get everything sorted while I have the added room to work. I think I have it figured out but wanting to have my plan looked over.

Old setup - 4 wheel 11" drum, manual 1" oem master cylinder, OEM distribution block, roll control

New setup - 10" front discs w/ sliding calipers (retain rear drum setup), manual 1" Wilwood Compact MC (4 bolt), Wilwood proportioning valve, same roll control

The Wilwood proportioning valve I have mounts to the master with a bracket and has front/rear inlet and front L/R and rear outlets which from what I can tell should replace the stock distribution block. My plan is to make 2 new lines for the front brakes and a small jumper for the rear with a union - does this sound OK?

From what I have read the residual pressure valve was built into the OEM master cylinder, so I have a 10lb valve from Wilwood I was planning to plumb into the rear line - is my thinking correct? And does it matter where in the line I plump the valve in? Closer to the master cylinder is what I have read.

My other thought was to run a single line proportioning valve on the rear line and retaining the stock distribution block - any reasons this would be better? I would still need the residual pressure valve but would not need to make as many new lines (car already has roll control so that complicates things a bit too)

 

[R/T Boy 67]

If it is easier, I would keep the stock block and plumb the prop. valve into the rear line. If the rear cylinders are somewhat new, then the residual valve is not needed. It is just another potential leak. Back in the day the factory used 2lb valves.

 

[andrewwoz]

Would the prop valve need to go after the block for the rear line? I know the the block has that valve in it for the brake warning light on the dash, is that its only function or would the pressure differential cause other issues?

 

[Dave6T4]

From what I am reading here, you are planning to use your OEM drum brake master cylinder? You should use a master cylinder made for a disc brake system. It not only has a larger reservoir for the the disc brake circuit, but also does not have a residual valve in that circuit, allowing the pressure to fall back to Zero, and let the piston to retract. This master cylinder would also have a residual valve built into the circuit for rear drum brakes, so you would not have to add another.
When I converted my 1964 Polara to front disc brakes, I used a combo valve from a 5th Ave. I recently had it fail in such a way that the shuttle valve locked up my front calipers. I replaced this combo valve with a Wilwood setup like you described, plumbing it in the manner you describe. It works great now.

 

[andrewwoz]

From what I am reading here, you are planning to use your OEM drum brake master cylinder? You should use a master cylinder made for a disc brake system. It not only has a larger reservoir for the the disc brake circuit, but also does not have a residual valve in that circuit, allowing the pressure to fall back to Zero, and let the piston to retract. This master cylinder would also have a residual valve built into the circuit for rear drum brakes, so you would not have to add another.
When I converted my 1964 Polara to front disc brakes, I used a combo valve from a 5th Ave. I recently had it fail in such a way that the shuttle valve locked up my front calipers. I replaced this combo valve with a Wilwood setup like you described, plumbing it in the manner you describe. It works great now.

No I'm installing a 1" bore Wilwood compact master cylinder (no residual valves)

 

[R/T Boy 67]

I am assuming you have a disc brake master, as it is a wilwood. The prop valve goes after the junction block. The residual valve was to prevent fluid from leaking out under no pressure situations, and from drawing air in on the return stroke. Newer wheel cyl. prevented this by using expanders or conical springs that kept the rubber cups in constant contact with the bore.

 

[andrewwoz]

From what I can tell Wilwood just sells 1 MC (bore size varies) and it will work for either disc or drum, it just does not have a residual pressure valve in it.

 

[gkent]

Residual valve is not necessary.

The problem with the Wilwood prop valve is the two OUT front lines - not ideal if you're installing a line loc. With a line loc you want a single IN and a dual OUT - one for each caliper. You should plug one of the front OUTs in the prop valve - run the other front OUT to the line loc IN then each OUT on the line loc to each caliper.The rear line from the prop valve goes direct to the rear. The built-in switch takes care of the brake "warning" light.

The residual valves were present to hold pressure in the old wheel cylinders. Newer wheel cylinders do not require the residual valve(s)

A 1" master cylinder bore should work nicely - you will have a fair bit of pedal travel but it should not take much effort - great for manual brakes.