CPP 64-67 Nova Stock Spindle Disc Brake Kit - Final Steps And Results
This page describes bleeding the system, adjusting it, and the final results of the install.
[WARNING/DISCLAIMER: use this information at your own risk, modifying automobile brake systems can lead to dangerous situations, always have a trained mechanic check your work, I take no responsibility for the results, you've been warned, you're on your own...]
Master cylinder bench bleed:
I was a good do-bee and did the bench bleed. I couldn't get the front circuit
to pump anything, then I read that the front is based on the rear pressure,
and won't pump until the rear is at a certain minimum pressure. Wait and bleed
the master cylinder after you have it on the car, but before you have done the
final connection of the brake lines.
CPP has a basic guide to bleeding brake systems on their website. I tried several methods of bleeding the system...with various degrees of success. I wasn't happy with any of the results. I finally bought some 'Speed Bleeder' bleed valves, and...that helped things immensely. I highly reccommend them. (For the record, the front calipers use part number SB1015, and the rear drums use part number SB51624.)
Bleeding the rear circuit was pretty straightforward. That I did with the 'helper pushing the pedal' method. When I got the SpeedBleeder valves, it gets even easier:
1 Fill the MC fluid reservoir with brake fluid
2 Open the right rear (RR) bleed valve, and connect a hose from there into a drain container
3 Press the brake pedal down slowly 3-4 times, or until fluid (and no air) comes out of the bleed valve.
4 Close the RR bleed valve
5 Repeat for LR. Make sure you keep the MC fluid reservoir topped off properly
I had trouble bleeding the front brake circuit. Part of the problem (as I discovered later) was that I had some leaks at the fittings that were letting air in. Make sure that all connections are tight and leak free. Do NOT use teflon tape on any of the brake line flare nut threads, or on the banjo fitting on the flex line. If they are assembled properly, they will not leak.
Once the rear circuit was bled, the method that finally worked for the front circuit was:
- Set up the proportioning valve to turn the rear circuit 'off'' temporarily:
1 set the balance (1/4" allen) at midway through it's travel
2 set the force (1/8" allen) to lock out rear (CW all the way)
- Prep for bleeding:
3 disconnect the front line from the MC (leave the rear line connected)
4 connect a line from the front MC connection looping back into the MC reservoir
- Prime the calipers and lines:
5 open the LF bleed valve
6 use a big sryinge or mityvac to force fluid in to the disconnected front line until fluid runs out of the bleed valve without bubbles
7 close the LF bleed valve
8 repeat 5-7 for the RF
- Bleed the MC:
9 make sure the end of the tube (from step 4) is completely in the fluid
10 slowly push the brake pedal to the bottom of the stroke and release it
11 wait 5-10 seconds
12 repeat 9-11 until no bubbles come out of the tube
- Bleed the circuit:
13 remove the loopback tube and reconnect the front line to the MC
14 open the LF bleed valve
15 slowly push the brake pedal to the bottom of the stroke and release it
16 wait 5-10 seconds
17 repeat 15-16 until fluid runs out of the bleed valve without bubbles
18 close the LF bleed valve
19 repeat 14-18 for the RF
That's kind of overkill, but...it worked for me...after I unsuccessfully tried a bunch of other methods. Note the paper towel under the MC. That is to make sure that there are no leaks at the brake line connections. If you get any drips, stop and fix the leak before you continue. If you have a leak, you will at be allowing air into the system, which can lead to spongy pedal feel, or eventual complete loss of braking function. Make sure you check ALL of the connections, at ALL of the junction points.
Also make sure that all of the bleed valves are closed, and the rubber covers are installed to keep the dirt out.
Make sure you adjust the balance and pressure settings before you go for the first ride!
Adjusting the MC:
The CPP website has the instructions adjusting the MCPV-1 but here is the basic process I used:
There are two adjustment hex screws on the rear side port on the unit. (Fig 4):
The 1/4" screw controls the front to rear balance. Turning it counterclockwise (CCW) will increase the braking force on the front circuit. Turning it clockwise (CW) will increase the braking force on the rear circuit.
The 1/8" screw limits the maximum rear brake pressure. You can increase the pressure to the rear brakes by turning the screw CCW. You can decrease the pressure by turning it CW. Note that if you turn this screw all the way CW, you will cut off ALL braking force to the rear brakes. Make sure you have at least 1/8 turn CW of travel left.
1 Adjust the 1/4" screw to midway through it's travel. Turn it all the way CCW until it stops. Then count the turns as you turn it CW until it stops. Turn the screw back CCW one half of that number of turns.
2 Adjust the 1/8" screw to midway using the same method. Make sure you ahve at least 1/8 turn CW of travel left.
3 Verify that the brakes are engaging by letting the car SLOWLY roll forward, and then pressing on the brakes. Use the emergency brake if the car does not stop. If you can't get past this test, DO NOT CONTINUE until you have corrected the problem. Usually the problem is that there is still air in the brake lines that needs to be bled off, or there is a leak somewhere in the system.
4 Once you have verified that the brakes are working, do several more test brakings, increasing the speed each time if the brakes are operating as expected.
5 Brake hard enough for the tires to skid. Make sure that both the front and rear brakes are locking at the same time. If the fronts are grabbing before the rear, move the 1/4" screw CW to shift the balance more towards the rear. If the rears are locking up first, turn the screw CCW instead. It's best to make SMALL adjustments, 1/8 to 1/4 turn per test.
6 Adjust the rear braking pressure using the 1/8" screw 1/8 turn at a time until the rear brakes are just barely not locking up on a hard stop.
The finished product
It's done...and it's fantastic! I took it for a couple of turns around the block, and I'm very impressed. I want to do some more experimenting with the proportioning valve settings, but I am pleased with it even with the minimal tweaking I did so far. I have a new problem now...it stops **so well** that the passenger bucket seat flops forward. Anyone know how I can retrofit a seat latch?
I did some before and after testing of the brakes using a G-Tech meter. 5 tests each. 60-0 stop distances in feet. Stock rear drum brakes in both tests.
Before (stock drum brakes, stock 1967 dual-chamber master cylinder):
After (CPP stock spindle front disc brakes, CPP MCPV-1 master cylinder):
Same road, same driver, same temps (about 55*) Huge improvement, over 100' shorter on average.
(I am not a professional 60-0 driver, so don't go comparing it to other cars' stop distances in magazines that use professional drivers. I was just trying to compare the before and after to show the improvement.)
Drum setup (drum, backing plate, hub, shoes, hardware) 25 lbs/side
Disc setup (rotor, caliper bracket, calipers, hardware) 29 lbs/side
I was expecting much more of an increase (like 10-15 lb/side) so I was pleasantly suprised to see it was only 4 lbs/side.
Unless otherwise specified, all text and images on this page are © Copyright 2006 by Pat Mancuso.