Update On Brake Proportion Valve Test
Thread Starter
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Update On Brake Proportion Valve Test
http://forums.corvetteforum.com/zero...334905#3334905
Well.... finally did the test... 1970 Vette... LS5.. power brakes... just completely removed the entire brake system, new caliper kits, original M/C rebuilt, converted to DOT 5... disassembled the "proportioning valve" (really just a switch) & cleaned it out to verify it was working 100% correct... it wasn't, but it is now.
All calipers are SS sleeved Delco, with stainless pistons from SSBC.
Master cylinder is the original 1970 unit, original bore size, un-sleeved with bleeders.
Here is what I did:
Made a special M/C cover with holes in the top for tubing connections.
The gasket was made out of painted cardboard and has holes for the fluid to return to the chamber. Fluid is DOT 5 so there are no contamination issues.
I disconnected the male steel fitting at the left (drivers) front brake hose, and attached a custom made female fitting and tubing connection.
I ran tubing from the line back up to the special test M/C at the front chamber (front brakes chamber).
I plugged the caliper flex hose and removed the caliper from the car.
My driveway has about a 15* slant to it...
I backed the Vette up the hill and let it roll back down... toward the garage.
Here is where "faith" has value.
Absolutely no brakes until the brake light came on... and then only enough braking to stop the car from rolling. In a "panic" stop.. kiss your butt good-bye.
The brakes only functioned minimally, and ONLY when the brake light came on. As soon as I let up on the pedal enough to make the light go off, no more brakes.
I repeated the roll/stop more than 20 times. The cars reaction was 100% consistent.... very little brakes, and only when the light came on when the pedal was at the floor.
Next test was to see how much pressure I could generate with the pedal at the floor... car not moving.
The LS5 could be stalled when I held the idle up and braked hard while letting the clutch out. I repeated this test consistently as well.
So there ya have it. We have tons of pictures because we took Jennys 1980 valve apart too... it is designed different, but we will not be testing her car.
As soon as we find the time to sit down... we will post some pics.
Tom
Well.... finally did the test... 1970 Vette... LS5.. power brakes... just completely removed the entire brake system, new caliper kits, original M/C rebuilt, converted to DOT 5... disassembled the "proportioning valve" (really just a switch) & cleaned it out to verify it was working 100% correct... it wasn't, but it is now.
All calipers are SS sleeved Delco, with stainless pistons from SSBC.
Master cylinder is the original 1970 unit, original bore size, un-sleeved with bleeders.
Here is what I did:
Made a special M/C cover with holes in the top for tubing connections.
The gasket was made out of painted cardboard and has holes for the fluid to return to the chamber. Fluid is DOT 5 so there are no contamination issues.
I disconnected the male steel fitting at the left (drivers) front brake hose, and attached a custom made female fitting and tubing connection.
I ran tubing from the line back up to the special test M/C at the front chamber (front brakes chamber).
I plugged the caliper flex hose and removed the caliper from the car.
My driveway has about a 15* slant to it...
I backed the Vette up the hill and let it roll back down... toward the garage.
Here is where "faith" has value.
Absolutely no brakes until the brake light came on... and then only enough braking to stop the car from rolling. In a "panic" stop.. kiss your butt good-bye.
The brakes only functioned minimally, and ONLY when the brake light came on. As soon as I let up on the pedal enough to make the light go off, no more brakes.
I repeated the roll/stop more than 20 times. The cars reaction was 100% consistent.... very little brakes, and only when the light came on when the pedal was at the floor.
Next test was to see how much pressure I could generate with the pedal at the floor... car not moving.
The LS5 could be stalled when I held the idle up and braked hard while letting the clutch out. I repeated this test consistently as well.
So there ya have it. We have tons of pictures because we took Jennys 1980 valve apart too... it is designed different, but we will not be testing her car.
As soon as we find the time to sit down... we will post some pics.
Tom
