Author Topic: JL8 master cylinder  (Read 6170 times)

KurtS

  • CRG Coordinator
  • *****
  • Posts: 4447
    • View Profile
JL8 master cylinder
« on: May 11, 2016, 08:04:03 PM »
Looking for confirmation of the JL8 master cylinder code. Is it US or something else?
JL8's don't have the residual pressure valve for the rear brakes. Maybe that was part of the master cyl assembly and the master cyl's are the same.
Kurt S
CRG

bcmiller

  • CRG Member
  • *****
  • Posts: 1790
    • View Profile
Re: JL8 master cylinder
« Reply #1 on: May 12, 2016, 12:19:40 PM »
 I believe the JL8 master cylinder used a larger piston diameter. Possibly the same as the 4 wheel disc Corvettes.
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
Looking for 68 Camaro with body number NOR 181016

Stingr69

  • Hero Member
  • *****
  • Posts: 554
    • View Profile
Re: JL8 master cylinder
« Reply #2 on: May 12, 2016, 01:00:51 PM »
I can't see how the MC/Booster assembly could be a "US".  The AIM suggests the assembly is different from "US" as it specifically refers to a separate parts list to find that item when the option was ordered.  From a functional standpoint it makes sense that it would need to have a different volume for the calipers VS the wheel cylinders.  I don't know what it should be, but I doubt the "US" was used.

paceme

  • Hero Member
  • *****
  • Posts: 609
    • View Profile
Re: JL8 master cylinder
« Reply #3 on: May 12, 2016, 01:39:46 PM »
Both JL8's I owned had the standard US master cylinders and worked perfect.
Steve Shauger
Vintage Certification™ Program, Providing Recognition And Status To Unrestored Vehicles. Website www.vintagecertification.com
Yenko.net- The Supercar Registry

RS_COPO_Canuck

  • Member
  • ***
  • Posts: 64
    • View Profile
Re: JL8 master cylinder
« Reply #4 on: May 12, 2016, 02:54:53 PM »
I seem to remember they used the US master but deleted the proportioning valve?

Bryan302

  • Member
  • ***
  • Posts: 179
    • View Profile
Re: JL8 master cylinder
« Reply #5 on: May 12, 2016, 04:03:14 PM »
Several things lead to suggest that the cylinders are different!

#1, on page 126 of John Hooper's book shows a JL8 master cylinder, and is quite obvious that it is not a 309 US cylinder.

#2, the chassis broadcast codes are clearly different, the CU code for a US cyl. and a CX code for a JL8 cyl.  If they were the same, there would not be any need for a different code.

Bryan
Bryan S.
1968 RS Z/28, 12E, PNT R2, TR 749
1969 Z/28 X33, 05A, PNT 52 52, TR 719, endura bumper

69Z28-RS

  • Hero Member
  • *****
  • Posts: 4428
  • owner since 4-Apr-1976
    • View Profile
Re: JL8 master cylinder
« Reply #6 on: May 12, 2016, 04:16:53 PM »
Bryan,

As Kurt suggested earlier, perhaps those 'CU or CX' codes included the complete brake MC arrangement, including (or not) the residual pressure value (in the MC outlet for the rear), the metering valve, and perhaps even the proportioning valve.   If that code includes these additional components (or not), then the 'US' coded (309) MC could have been used for either disk/drum, or disk/disk systems.   I know of an original '69 SS Camaro with JL8 brakes which I need to try to get access to it and take some photos.  If I can do that, I'll post here.

Given the high incidence of the JL8 rear disk brakes having been *moved* from car to car, and *added* to cars not having come from the factory with it, I'm a bit skeptical of most/any? photos which have appeared over the years in books and magazines, as the owners generally 'attest' to the JL8 system being *original* to their cars (whether they know that fact to be true or not!)...
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

bcmiller

  • CRG Member
  • *****
  • Posts: 1790
    • View Profile
Re: JL8 master cylinder
« Reply #7 on: May 12, 2016, 04:39:29 PM »
Its tough to get rock solid data points now 47 years later on things that were quite rare to start with, but we have to try.
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
Looking for 68 Camaro with body number NOR 181016

bcmiller

  • CRG Member
  • *****
  • Posts: 1790
    • View Profile
Re: JL8 master cylinder
« Reply #8 on: May 12, 2016, 07:12:28 PM »
At least on Corvettes, I believe power brakes cars got the larger bore (1.125 inch) master cylinders, while non power brake cars got the 1 inch diameter.

Steve Wright posted something in a 2008 thread and it had US for the larger bore power disc use in 69. Not sure if known information has changed now.
Bryon / 1968 Camaro SS 396 - now 468 ci, M21, 12 bolt
Looking for 68 Camaro with body number NOR 181016

1968RSZ28

  • Hero Member
  • *****
  • Posts: 6166
    • View Profile
Re: JL8 master cylinder
« Reply #9 on: May 12, 2016, 07:34:55 PM »
JM's '69 Camaro Z28 Fact Book says the JL8 master cylinder is identical to the standard '69 Z28 master cylinder and is stamped "US".

Paul

WorkinProgress

  • Member
  • ***
  • Posts: 79
    • View Profile
Re: JL8 master cylinder
« Reply #10 on: May 13, 2016, 08:40:24 AM »
Kurt, all the original JL8 cars I have seen have the US stamped master cylinder.

                                                            - Warren

                                                                 

68camaroz28

  • Hero Member
  • *****
  • Posts: 1628
    • View Profile
Re: JL8 master cylinder
« Reply #11 on: May 13, 2016, 10:21:11 AM »
The only car I ever checked had a BA but that might have been changed when the car was restored in the 90's or even before for some reason. The BA master cylinder with that JL8 car worked excellent. Not sure what differences are between a BA and US but assume minimal.
Chick
68 Z/28 NOR 01B Orig motor/trans/rear
69 Z/28 NOR 07A Orig Block & GM Cross-ram/carbs
69 L34 Rest. Nova Father/Son Car
69 L78 Surv Nova Purch 4/69 31K miles
67 L89 Corv Tribute
68 Corv 427/400 Orig motor
07 Corv Z06
R 68Z build- http://www.camaros.net/forums/showthread.php?t=182584

69Z28-RS

  • Hero Member
  • *****
  • Posts: 4428
  • owner since 4-Apr-1976
    • View Profile
Re: JL8 master cylinder
« Reply #12 on: May 13, 2016, 02:51:41 PM »
From my copy of the Oct '70 Parts and Accessories Catalog, under Sec 4.65   CYLINDER ASSY. - Hydraulic Brake Main...
...
69   Chevy, Camaro w/Disc Brakes   5463751    1  28.65    (1-1/8" dia. cyl.) (stamped U.S.)
69   Chevelle, w/Disc Brakes            5469399    1  35.55    (1-1/8" dia. cyl.) (stamped B.A.)


this raises some questions: 
1) Why does it list both 'Chevy', and 'Camaro' with Disc brakes??  for the US MC?
2) Why does the BA MC (for the Chevelle) show a 'price' which is 20% higher than the US MC?

There *must* be some substantial difference for the difference in price, AND the fact that two different MC are listed even though they each have the 1-1/8" piston bore??  Both are still in the catalog almost a year after the end of production for the '69 models.
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I 
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

bertfam

  • CRG Member
  • *****
  • Posts: 2994
    • View Profile
Re: JL8 master cylinder
« Reply #13 on: May 13, 2016, 03:54:55 PM »
From the July 1st, 1969 "Heavy Duty Operation Parts for Passenger, Corvette and Camaro" manual:



From the June 24th, 1971 "Standard Parts Service and Maintenance Products" manual:



The bottom picture isn't very good, but you can clearly see the 5463751 Master Cylinder code "US"

Ed
Ed "Bert" Bertrand
email me!

luv2sixty9

  • Member
  • ***
  • Posts: 107
    • View Profile
Re: JL8 master cylinder
« Reply #14 on: May 13, 2016, 04:04:04 PM »
309 MC with US Stamp is the correct one

Dave
1967 Z/28 Butternut Yellow
1969 Z/28 Rally Green
1969 RS Z/28 Lemans Blue
1969 RS Z/28 Olympic Gold
1969 RS SS Pace Car
2010 Aqua Blue 2SS RS