Why is there some Z28's with 3908326 Rear Proportioning Valves and Some without

[dannystarr]

Hey Guys, anybody know why there is some car's that are equipped with the rear Proportioning valve and some car's that are not? You know, the one on the drivers side frame rail. I see lot's of car's with and without. The old story used to be that the car's that got it had A/C. And so the extra weight needed to be controled so the rear wheels would not lock up during hard braking. But that's on SS big block's and such. Z/28's never had the A/C on any of the 28,103 first gen cars. Why do I keep seeing some cars with them and some without? I met a guy back east who has 6 Z/28's all original. He might even hang out on this site. He said 4 of his car's have it and 2 don't. I just seen another car certified by Jerry M. in PA and it's ALL there, but has no valve. I'm gett'in pissed. What the hell is the deal with these valves. I also have seen them on some 68's but not other's. And if a 68' doesn't have it it scares me into think'in it ain't the real deal. Could Chevrolet really come up with this system and then just say to the guys on the assembly line... put them on when ya want? I have seen probably a hundred of 69's with it, and just as many without. Jerry never really decided to put this info in his book's??? It even show's it in the assembly manuals. Ok, I have rambled enough .......Danny

[77thor]

Let me start off by saying that I'm no expert.... I'm sure one of them will chime in....

My understanding is that all Z28's and SS's had the rear Prop valve on the frame under the drivers seat.
I'm not clear on the reason for the valve.... something to do with the higher horsepower/performance of those models??

[JohnZ]

What we know about the valve's usage is summarized here:

http://www.camaros.org/suspen.shtml#valve

Research continues on exactly what the vehicle configuration criteria were that required it and why it changed.

[1968RSZ28]

Let's all post whether or not our cars have a rear brake line pressure regulator valve.  Once we have enough data, Kurt will figure it out!   

I'll go first...

68  02C  LOS  Z22/Z28  NO rear brake line pressure regulator valve

Paul

[1968 Z28]

No valve.....see signature for vehicle.

[Gramps69Z]

My 10E Norwood 69 Z has it.

[fireZ]

My 02E Z28 from the LOS plant has it,I think it dates about 54 days before the car was built.

[dannystarr]

So there it is, I guess that's the latest. Just frustrating. And as some of you know, I collect these valves for fun. I know....I know....I think I am up to about 20 or so. In fact that reminds me, I need to get John Z and or CRG a new front and back picture of all of them. So if ya have any of these valves LMK. I may purchase them from ya.
Sure would be nice to know if Jerry M. kept track of all the cars he inspected, had the valve or not. AND what the julian date was on each valve. Maybe he did. Anyway to go to the registry of all these cars on the list for 67' 68' and 69'.....and email or contact them and ask? Takes about 30 seconds. Not like ya have to take any components off to find out. Then at least we could have the info on ALL remaining cars? I talked to some guy a while back and he said he wouldn't own a car if the valve date went farther back then 35 days from build date. What's the deal with that? I have seen them on original 23,000 mile cars with full doc's and it was 62 days back. Even FIREZ mentions his car at 54 days. I think everybody should add the date along with the info. Good idea??...Danny

[X66 714]

My 02E 68 z/28 from Van Nuys does NOT have that valve....Joe

[CNorton]

My late '69 (10C) X11 non-SS car that had J52 brakes had no valve.

[jacmac]

My 69 Z10  O4C L35 w\AC has one

[Marty]

My 01C LOS 68 SS-396 has the valve, date is 3447. The car has front disc brakes.

Martin

[68Zproject]

05D 68 Z no valve.  I had a 68 SS that had it and I have no idea of it's build date.

[dutch]

  My 02D '68 Z 2/8 does NOT have the valve...

[BlackoutSteve]

Everyone here with Zs are responding.. What about SS 350/L48 owners? That's the chapter in the AIM where the valves are listed (L48-B3). One would expect 100% of those cars to have the valve..