rear portioning valve info

[Nova Research Project]

bbbenny;

Your welcome, glad I can help!

[SS4Real]

Did 1970 Chevelle's with front disc/rear drum also have this valve? My front brakes are fine, but the rear brakes frequently lock up since I had the power booster removed and reinstalled when it was replated. How is this adjusted?

[Musclecarkid]

The rear brake pressure valve was standard on all 70 Chevelles with factory front disc brakes. There were 2 designs available. Early 70 (actually 69) built cars used a valve with an "N" stamped on it. After 12-23-69 it was replaced with an "S" stamped valve. The "N" was rated at 250psi and the "S" was 400psi. Also all 70 Monte Carlos came with this pressure valve because they all had front disc brakes. The difference between the Camaro and Chevelle valves is the mounting bracket is reversed to allow a different mounting position. I have 5 of these dated from 260-9 "N", 022-0 "S", 023-0 "S", 079-0 "S", and 127-0 "S". I'm sure most other 1970 GM A-Body cars used this as well. Some early Camaros with AC and Disc Brakes or Big Blocks also may have one. All 70 Z/28 and T/A's had a simular valve bolted to the distribution/brake warning valve under the master cylinder. Most of the pressure valves I have are dated about 2-4 weeks before the build date of the vehicle.

[JoeG]

musclecarkid,
Good info---Thanks [img]/ubbthreads/images/graemlins/biggthumpup.gif[/img]--JoeG

[Musclecarkid]

Thanks Joe G, I really researched that little rear brake pressure valve. GM found it necessary to use that valve to eliminate rear wheel lockup in a panic stop. In 71 GM replaced the front metering valve, the rear pressure valve, and the brake warning switch with a one piece combo valve mounted on the left front frame rail on A-body and under the master clyinder on F-body cars.

[SS427]

Kevin,
research must be your middle name! Very good information, thanks for sharing. [img]/ubbthreads/images/graemlins/biggthumpup.gif[/img]

[Musclecarkid]

Yes I am thinking of changing my middle name to "Research". Has a nice ring to it. "Kevin Reasearch Kid". But seriously I just happen to have all the right books in my library. If your interested, the 1970 Chevelle/El camino/ Monte Carlo Assembly Manual has this rear brake valve info in UPC 5 on pages 134-135. The early "N" stlye valve was added to the 70 production on 8-18-69 and is pt # 3980770 which was repaced by the later "S" style valve on or about 12-23-69. As for how I found the pressure ratings, I just happen to have an original 64-70 Chevrolet (P&A 30A) Parts Catalog and if you look in Group 4.690 (Valve Assy-Bracket, Rear Brake pressure Regulator) you will find all these valves listed. 67-69 Camaro #3908326, 70 Nova #3982304, 70 Camaro #3980978, 70 Chevelle 1rst design "N" 250psi #3980770, and 70 Chevelle 2nd design 'S" 400psi #3987805. It just so easy when you do a little "Research". Thanks for all the kind words. Any more Questions, let me know, I have all the early Chevy Parts Books. Bought them at Carlisle about 15 years ago for $100. Hope I have helped you all.........Kevin