I have a few questions about the front disk conversion on the 1966 Cutlass. Verifying my work with guys that have done this before is pretty cool.

As I am hooking up the booster linkage to the brake pedal arm, do I use the upper hole or lower hole to couple together? It could go in either, but I couldn't take the pretzel move any longer, straddling the car lift, up under the dash, so I clipped the pin in the first hole I could find.

Is there any need to use the spacers between the master cylinder and the booster? The car I removed it from did not use spacers. The original drum brake master cylinder had two spacers between the fire wall and the MC. Comparing the two side by side, the linkage looked to be the same length from mounting flanges to the center of the coupling pin.

I plumbed the proportional valve like the car it came from, though I question how it went together. The front port of the MC feeds the front, center port on the proportional valve; the rear port of the MC feeds the top, rear of the proportional valve.

 

Hey:
Did this same job on my 66 Cutlass last summer, I don't remember any spacers coming w/ the complete kit I bought. I do think I had to drop to the lower hole in the brake pedal though, I am pretty sure the new booster/MC angle requires it, I would go check but we took the entire car back apart for a resto. That is probably the best thing you could have done for your car, even if the drum brakes are in excellent condition, if you don't stop in a few feet, you are just along for the ride.
Thanks Ron

 

Thanks Ron, this was the main upgrade I planned as I bought the car.

Did you use the proportioning valve from the upgrade kit or a stock GM valve?

Take care,

Larry

 

The upper hole is for manual brakes, lower for power. The power brakes require a shorter lever arm, which reduces required stroke. Using the upper hole with a power booster puts an excessive angle on the pushrod.

I've never seen spacers on a booster.

 

Thanks for the tips Joe, the cross section of the valve assembly is helpful. It is shaped a little different but the ports are exactly the way I have it routed.

The pedal linkage is correct too, I remember thinking that forcing to the upper linkage point would have forced the booster up too high. Better to confirm the guess.

When the rear distribution block arrives, I will finish the rear lines and bleed the system. I appreciate your help as usual...

Larry

 

Hey Joe,

Can you have a look at a photo of the proportional valve and let me know if you can confirm the year of car it was from?

I am guessing at a 1970; I have been looking at cars '71 and up at it looks like they have valves like the style you sent in the port identification diagram.

I harvested the disk brake system from a '67 442, and I previously thought it may have been original until the shop I got the brake line kit from (Fine Lines) could not find a listing for a '67 with front disks.

After hand bending the lines from the MC to the valve, I am not quite happy with the outcome. I am thinking of ordering these two lines, but without knowing the year, I am just rolling the dice again. I could have a second go at bending them, now that I know how I want them to look.

Thanks for the tips

Larry

 

That is NOT a proportioning valve, it is simply a distribution block from a drum brake car - 1967-1972. Note that the 67-70 disk brake cars used this same distribution block with a separate metering (proportioning) valve mounted under the master cylinder. Starting with the 1971 model year, GM combined the metering valve with the distribution block to create the combination valve I showed in the drawing above. This was done to reduce parts count and save cost. Either configuration works fine, but you cannot use the distribution block in your photo without a separate metering valve, shown below.

 

I do have the metering valve installed, as you have in the photo, luckily it was all intact from the parts donor car.

Is there any truth the set-up I am using having more predictable rear brake control than the packaged metering / distribution block typically purchased with the aftermarket brake line kits?

As I ask the question, I realize that advances in brake engineering typically improve over the years. Maybe I took some bad advice. We will see how the car responds.

 

There is no functional difference. As I noted above, GM went to the combo valve simply to save assembly line labor (and thus cost) and to eliminate some potential leak points by reducing the number of flare nut fittings.

 

Thanks Joe! I appreciate the help...

 

I have had the car out for two joy rides and it is clear that I have an issue to clear up with the brakes. Otherwise, the car is working great!

All wheels are dragging, even after I lowered the fluid level in the master cylinder to roughly 3/4" from the top to allow for expansion.
As everything cools with the car on the lift , I can spin the rear wheels by hand in 10 minutes and the front wheels in 20 minutes. None seem to have excessive drag while cool.

The distribution block, the proportioning valve, and the rear wheel cylinders are the only used parts in the hydraulic system.

One final clue, it was a real chore the bleed the rear brakes, even while using a vacuum pump.

Would the heat from the exhaust manifold cause line pressure to build in the break system? I mounted it roughly where the original 1966 block was originally. Any ideas! I am thinking there may be a restriction in the distribution block.

Larry