1969 Z-28 pressure valve
 

do all 1969 Z-28's have the brake pressure valve on drivers side frame rail?

no

can u elaborate on that - and why please?

----I can understand your response!....Bill S

i understand the comment - and have looked for why that is, so I was looking to get better educated on this as i have a different understanding - but data is king in this industry.

appreciate the background if you can share WHY, not all 69Z's would not have this valve?

My January Z never had one

"The '67 Chassis Service Manual says it was used on Camaros with air conditioning, and the '69 manual says it was used on Camaros with 12-bolt rear axles; usage varied, and no precise pattern of options or equipment has been observed that would dictate its presence. "

Source: CRG https://www.camaros.org/brakevalve.shtml
Author: John Hinckley

:biggthumpup:

Don't forget, all the brake valves in the CRG report can be rebuilt. Kits available from Muscle Car Research: https://www.musclecarresearch.com/

I documented my rebuilds here: https://www.camaros.net/threads/1969...valves.483596/

My jL8 Z28 doesn't have one

The pressure regulator valve under the master had two functions. It delays the engagement of the front disc, so the car did not nose dive when brakes were applied and also provided 30-40 psi to the rear wheel cylinders. The ensured the rear drum shoes engaged prior to the front calipers.This applies to front disc, rear drum configuration.

Updated:
From CRG/ John Hinckley Brake valve report
Rear brake line pressure regulator mounted on subframe function:
"The valve limits the amount of hydraulic pressure, at a controlled rate, to the rear wheels in proportion to the amount of pressure to the front wheels. This action prevents the rear brakes from locking up before the full effective braking effort is produced by the front disc brakes."