1969 Z-28 pressure valve

[Nova Research Project]

Originally Posted by Steve Shauger

If i recall the function of the valve on the frame was to keep a specified amout of pressure so the drum shoes did not fully retract when no pedal pressure was applied. This valve prevented a delayed engagement of the rear drum shoes, when brakes were applied.

Steve,

The November 69 Chevrolet Service News quoted in John Z's CRG report was specifically about the 70 Nova with Disc Brakes. CSN called it a Pressure Regulating Valve. It prevented the rear brakes from locking up.

Eddie,

The Pressure Regulating Valve (3982304) was used on all 70 Novas with Disc/Drum brakes. The valve was on the subframe from the first part of 70 production. Later production is was under the master cylinder.

While researching this I noticed that the Camaro valve (3908326) looks just like 3982304. Parts books states that it was for:

67 with AC, (not sure why)
67-69 396 Except 4 Wheel Disc Brake,
68-69 350 Except 4 Wheel Disc Brake,
68-69 327 w/4-Speed Except 4 Wheel Disc Brake,

This would indicate that the cars came standard with Disc/Drum should get it. This was safety feature after all. Not only did the Nova get it in 70, but so did the Chevelle w/Disc Brakes. There were two Chevelle designs.

JL8 Z's wouldn't need it. 12 bolts axles generally went on cars with front disc bakes. Maybe the 302 in the Z did not necessitate such lockup protection. Other than that, it is a mystery why there is no completely logical pattern based on CRG data collection.

Greg.