1969 Z-28 pressure valve

[1967Z28]

Valve usage is not consistent between Norwood and Van Nuys either. There is no completely logical pattern based on CRG data collection. Chevrolet literature says one thing and data says something else.

[1967 4K]

Ask Mike Gibbons. Is it even necessary. 🤷

[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.

[Kurt S]

There's more under this link:
https://www.camaros.org/suspen.shtml#valve
Some JL8 cars have the valve, btw.

[enio45]

Thank you guys, I see not definitive pattern for this - and unfortunately no real pattern either.

Recognize this was not my thread but Georges, i appreciate hearing the input and thoughts etc.

I was under the impression this was a pretty clear answer, especially for the 69Z cars, all had 12 bolts, boosters and masters with distribution valves and dump valves.

Obviously not.

Thanks again.....



I got it - there is conflicting info on what is right or wrong or no real definitive pattern for the application.

[Mr.Nickey Nova]

My 69 Z built late June does have the valve mounted on the subframe. Hope this helps!! Greg, my 70 L34 Nova does not have the valve on the subframe and is a January built car. I take it that the early Novas go up to November or December??

[Nova Research Project]

Originally Posted by Mr.Nickey Nova

Greg, my 70 L34 Nova does not have the valve on the subframe and is a January built car. I take it that the early Novas go up to November or December??

Precisely, Willow Run made several production changes at the end of 1969. Not having it on the subframe in January makes sense. What build week in January? I can compare with the database.

Greg

[3X24SPD]

A topic that I have wondered about for a long time.
I was working with the understanding that all 69 Z28 & BB cars had them.
12 bolt applications makes sense- as does not required on JL8 cars.

However, my NOR 02B X77 does not have one- and have always wondered why.
Was thinking perhaps someone had replaced the subframe at some point in its early life.
Though it did appear to be quite unmolested & original when I completely disassembled & rebuilt the car in 2020.

[mhm1966]

Not to change the subject, but I realize that some cars came with the pressure release valve and some cars did not. My car is a 03D build and it has the valve. Did all the sub-frames coming down the assembly line have the hole for the provision for the valve.

[169indy]

^^
1968 LOS Z28
Subframe has provision No Valve:
I would hazard a guess that ALL sub frames were spec to have provisions i.e. holes for locating tang and self tapping screw for install of valve as needed.