Brake Valve on the side sub frame for a 69 camaro

[Dusk Blue Z]

sah62 PM sent.

Mike

[sah62]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: m22mike</div><div class="ubbcode-body">Both these valves have been discussed at length over at CGR, and explained by John Z in detail.</div></div>

Wow, as I'm reading through eBay ads I see what you mean about the confusing nomenclature. Lots of people don't seem to know the difference between the pressure differential, proportioning, and metering/hold-off valves. I'll have to add that info to my web site.

[mockingbird812]

Scott,

I for one am ignorant (or have misinformation) and wouldn't mind a refresher on each of these components and how they interrelate.

thanks!

[169indy]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sah62</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 169indy</div><div class="ubbcode-body">O-rings are easy to find (Viton) material is a good choice. The shaped seals are going to be he difficult items to source.</div></div>

Viton is not compatible with automobile brake fluid [1]. EPDM is the way to go. The other seals are a little more difficult, but they're doable.

[1] One source: http://www.elderrubber.com/material.htm </div></div>

You are correct for the most part,
EPDM is Good for DOT 3,4, &amp; 5
VITON is in fact good for DOT 5

I use in Silicone based DOT 5 brake fluid.

REF:
2.2.4 Ethylene Propylene Rubber (EPR, EPDM)
EPR copolymer ethylene propylene and ethylene-propylenediene
rubber (EPDM) terpolymer are particularly useful when
sealing phosphate-ester hydraulic fl uids and in brake systems
that use fl uids having a glycol base.
• Glycol based brake fl uids (Dot 3 &amp; 4) and silicone-basaed
brake fl uids (Dot 5) up to 149°C (300°F).

2.2.7 Fluorocarbon (FKM)
Fluorocarbon (FKM) has excellent resistance to high temperatures,
ozone, oxygen, mineral oil, synthetic hydraulic fl uids,
fuels, aromatics and many organic solvents and chemicals.
Low temperature resistance is normally not favorable and
for static applications is limited to approximately -26°C
(-15°F) although certain compounds are suitable down to
-46°C (-50°F). Under dynamic conditions, the lowest service
temperature is between -15°C and -18°C (5°F and 0°F).
Gas permeability is very low and similar to that of butyl rubber.
Special FKM compounds exhibit an improved resistance
to acids and fuels.
Heat resistance
• Non-fl ammable hydraulic fl uids (HFD).
• Silicone oil and grease.
• Mineral and vegetable oil and grease.
Not compatible with:
• Glycol based brake fluids.


I have easy access to most material types. O-rings, It is as you state the shaped seals are a very big problem to source.

I like your site and efforts look very good and helpful

Jim

[169indy]

I like to study the Section 5 Brakes of any GM Chev Chassis Service Manual.

Definitions from them: 1968

A) &lt;&lt;SWITCH&gt;&gt; A New brake pipe distribution and switch assembly is mounted below the main cylinder. Front and rear hydraulic brake lines are routed from the main cylinder, through the brake pipe distribution and switch assembly, to the front and rear brakes. The switch is wired electrically to the brake alarm indicator light in the instrument panel. If a leak in either front or rear system occurs, the pressure differential (150-250 psi) during brake application will cause the piston to compress the springs and move (the piston) in the bore until it touches the electrical contact (grounding the circuit) which causes the parking alarm brake lamp on the instrument panel to light.

B)&lt;Lower Rears&gt;&lt;PRESSURE REGULATOR VALVE&gt;&gt; On certain models the rear brake hydraulic line is routed through a pressure regulator valve mounted on the left subframe rail. The valve controls the hydraulic pressure to the rear brakes resulting in the correct pressure balance between the front and rear hydraulic systems.

C)&lt;Upper Fronts-DISC BRAKE Car&gt;&lt; PRESSURE REGULATOR VALVE&gt;&gt;Models with disc brakes have a pressure regulator valve mounted below the main cylinder. The valve meters the hydraulic pressure to the front brakes resulting in simultaneous braking balance between the front and rear brake systems. This valve guards against premature lock-up of the front wheels when the brakes are applied.

I know my 69 Pace car stops very nice and maintaining a correct bleed and brake system maintenance should be considered one of any enthusiast first priorities. Going FAST is easy, Stopping is Critical.
Try stopping a 1925 Hudson super 6 at 35mph, external friction OD brakes on the REAR only, You have heard of ARMSTRONG steering, try one step above Fred Flinstone BRAKES

Jim W

[lzdick]

Jim, you have a PM.