Author Topic: JL8 master cylinder  (Read 22883 times)

KurtS

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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
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bcmiller

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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.
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Stingr69

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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.

Steve Shauger

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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.
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RS_COPO_Canuck

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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

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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
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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!)...
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bcmiller

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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 coupe - now old school 468 big block
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bcmiller

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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 coupe - now old school 468 big block
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1968RSZ28

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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

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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.

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68camaroz28

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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.
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69Z28-RS

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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.
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bertfam

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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

luv2sixty9

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Re: JL8 master cylinder
« Reply #14 on: May 13, 2016, 04:04:04 PM »
309 MC with US Stamp is the correct one

Dave
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bertfam

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Re: JL8 master cylinder
« Reply #15 on: May 13, 2016, 04:16:32 PM »
Quote
309 MC with US Stamp is the correct one

Dave, 5468309 is the CASTING number of the master cylinder and has no real bearing on the application. That casting number was used on multiple models and even multiple divisions in 1969 with different part numbers and codes, depending on the application.

Ed

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Re: JL8 master cylinder
« Reply #16 on: May 13, 2016, 04:44:56 PM »
It *seems* to be a fact that the JL8 factory installed brake system included the '309' cast MC with US stamp, and of course, as Bert points out, this doesn't necessarily mean that the parts are assembled the same.  Any differences should be reflected in the bill of materials (BOM) for the part number (PN).  But.. in this case, the same MC part number used on Camaros with  either JL8 OR J52 disk/drum brake systems.  I would assume that these 'master cylinder assemblies' were assembled completely at Delco-Moraine prior to delivery to Norwood or VanNuys, which raises the question as to 'when'how' were the differences in the residual pressure valve (an internal part of the assembled Master cylinder) accomodated?  Did Delco Moraine build them two different ways (with and without the rear brake residual pressure valve)?  OR did they build them with the valve and the assembly plant remove the valve from the rear outlet??  OR were the valves, springs, seats included as loose parts in the MC package, and the assemblers used what they needed to?  (curious minds want to know!).. :)

The CRG archive/reports section on brakes says this...
"1969 J52 disc brake systems and JL8 four wheel disc brake systems used similar master cylinders. The only difference between the master cylinders was the J52 master cylinder (code US) had a check valve in the outlet for the rear drum brakes, whereas the JL8 master cylinder did not have any check valves."

Since the same PN MC (5463751 ) was used for both brake systems, how was this difference accommodated?   The only answer I can come up with is that the differences associated with  the 5463751 master cylinder would have to be accommodated at assembly time??  but wouldn't the AIM reflect that?  (I just took a quick look at the AIM and didn't see anything on this issue?)...
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bertfam

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Re: JL8 master cylinder
« Reply #17 on: May 13, 2016, 05:10:35 PM »
Quote
Since the same PN MC (5463751 ) was used for both brake systems, how was this difference accommodated?

Gary, the assembly line part number was different than the service part number which is what I posted above.

For example, the assembly line part number for the 69 Camaro J52 master cylinder, as called out in the AIM (UPC J52, Sheet A2, item 1), was 5468165. This included not only the master cylinder, but the booster as well and it came to Norwood/LA as an assembly from Delco.

The same goes for the JL8 master cylinder. It would have come from Delco to Norwood/LA as an "assembly" (master cylinder and booster) with it's own part number (which is unfortunately unknown since the AIM doesn't show it).

Therefore, it would have been Delco that would be building the "assembly", and in the case of the JL8, not installing the RPV in the master cylinder.

Ed

JKZ27

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Re: JL8 master cylinder
« Reply #18 on: May 13, 2016, 06:25:13 PM »
Doesn't the service manual describe the check valve usage and, possibly, letter code usage? Also, it should show the RCV(residual check valve) service procedure per application since they're removable. Install only one check valve for front disc or no valves for 4 wheel disc.
John
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jdv69z

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Re: JL8 master cylinder
« Reply #19 on: May 13, 2016, 07:16:51 PM »
Quote
Since the same PN MC (5463751 ) was used for both brake systems, how was this difference accommodated?

Gary, the assembly line part number was different than the service part number which is what I posted above.

For example, the assembly line part number for the 69 Camaro J52 master cylinder, as called out in the AIM (UPC J52, Sheet A2, item 1), was 5468165. This included not only the master cylinder, but the booster as well and it came to Norwood/LA as an assembly from Delco.

The same goes for the JL8 master cylinder. It would have come from Delco to Norwood/LA as an "assembly" (master cylinder and booster) with it's own part number (which is unfortunately unknown since the AIM doesn't show it).

Therefore, it would have been Delco that would be building the "assembly", and in the case of the JL8, not installing the RPV in the master cylinder.

Ed


So was "US" stamped on master cylinder the same as the broadcast code for J52 master cylinder on the assembly line? If the JL8 cylinder is different, then the broadcast code would have to different. But is it possible that at Delco they used the same "US" stamped cylinder without the residual pressure valve rather than having it stamped differently? But then attach a tag (I'm assuming there was a broadcast tag attached to the assembly at Delco) with the correct broadcast code to the complete cylinder/booster assembly before shipping to the assembly plant? Is the broadcast code for the JL8 known?
Jimmy V.

bertfam

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Re: JL8 master cylinder
« Reply #20 on: May 13, 2016, 08:46:37 PM »
The Broadcast Code for front disc brakes/rear drum brakes was CU, and for 4 wheel disc brakes it was CX, so yes, they're different, and yes, the tag on the bail wire would be CU (front disc) or CX (4 wheel disc).

I don't have a service manual for 1969, so maybe someone could look that up. I'm not sure it mentions the 4 wheel disc brakes though.

Ed

JKZ27

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Re: JL8 master cylinder
« Reply #21 on: May 14, 2016, 02:08:35 AM »
In the 1969 Chassis Service Manual, there is a chart listing the master cylinder codes and their usage. Here's a few;
Camaro and Nova with power disc.......US
Chevelle with power disc....................BA
Corvette with power disc....................PG
"The two-letter identification stamp on the end of the master cylinder indicates the displacement capabilities of that particular cylinder."
There are no special service procedures for the master cyl in the 4 wheel disc section as it simply refers you to the Duo-Servo Brakes section.
John
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bertfam

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Re: JL8 master cylinder
« Reply #22 on: May 14, 2016, 03:02:03 AM »
Quote
There are no special service procedures for the master cyl in the 4 wheel disc section as it simply refers you to the Duo-Servo Brakes section.

Yeah, I didn't think there would be.

As for the same code being used for front disc/rear drum and 4 wheel disc master cylinders, I believe (and this is my opinion only) that since the JL8 option was rarely called for, if Delco got an order for the JL8 master cylinder/booster, they would simply pull a CU assembly, remove the RPV and retag it as a CX. This would explain why both master cylinders are stamped US.

Ed

bcmiller

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Re: JL8 master cylinder
« Reply #23 on: May 14, 2016, 04:15:41 AM »
That makes sense to me Ed.
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ZLP955

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Re: JL8 master cylinder
« Reply #24 on: May 14, 2016, 08:05:07 AM »
That is a good theory, especially as it seems the JL8 cars were scheduled in batches.
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69Z28-RS

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Re: JL8 master cylinder
« Reply #25 on: May 14, 2016, 01:00:56 PM »
OK Ed, that tells us how GM handled the difference in the factory (via a *different PN*) for a higher level assembly (and tag CX, CU, etc), but for someone with 4-wheel disk brakes on their car, who go into the parts department to purchase a replacement MC (for whatever reason), the service MC being the same PN would mean they got the same part.   Did that part include the RPV or not?  IF the MC PN does not include the RPV, springs, and seats, then the repair person would remove those parts from the old MC and install them in the new MC (problem solved), BUT.. if the MC PN (5463751) included those small items - which only seem reasonable to me - then people repairing a 4-wheel disk system with a new service PN would find themselves with their rear brakes not working correctly after replacement with a GM service part.   Is there any means to find how how that PN was defined??

In my experience, the PN *defines* the complete bill of materials for an item... and I don't know how a company's manufacturing and delivery system would function if this wasn't true.
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bcmiller

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Re: JL8 master cylinder
« Reply #26 on: May 14, 2016, 01:42:16 PM »
Quote from: 69Z28-RS
Is there any means to find how how that PN was defined??

I doubt it.

May have been included in a service note somewhere, but it is such a low volume item - it probably don't get much press.

Servicing one is covered well starting on page 5-16 of the 1969 Chassis Service Manual.  Mostly.

"No check valve is required for disc brakes" is specified - but they only mention the front, saying "the outlet boss to the front brakes will not contain a check valve and spring".  I guess I would read into that - those two items are not required in the outlet boss to the rear brakes either - if you have rear discs. But maybe I am assuming too much.

That's about all I can find if you want something in written format.
« Last Edit: May 14, 2016, 04:31:27 PM by bcmiller »
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 Camaro RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

bertfam

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Re: JL8 master cylinder
« Reply #27 on: May 14, 2016, 04:19:58 PM »
I agree with Bryon, and would go on to say that there may have been a "Chevrolet Dealer Service Technical Bulletin" or one of the monthly "Chevrolet Service News" editions that mentions this.

Ed

bcmiller

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Re: JL8 master cylinder
« Reply #28 on: May 14, 2016, 04:32:57 PM »
I looked in all of the 1969 Chevrolet Service News monthly publications, but could not find anything on JL8 Master Cylinders.

I will try to look in the Service Bulletins - but I don't remember there being any from when I looked through all of the ones I have about a year ago. But I don't have access to them all.
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big iron

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Re: JL8 master cylinder
« Reply #29 on: May 14, 2016, 04:46:24 PM »
Quote
There are no special service procedures for the master cyl in the 4 wheel disc section as it simply refers you to the Duo-Servo Brakes section.

Yeah, I didn't think there would be.

As for the same code being used for front disc/rear drum and 4 wheel disc master cylinders, I believe (and this is my opinion only) that since the JL8 option was rarely called for, if Delco got an order for the JL8 master cylinder/booster, they would simply pull a CU assembly, remove the RPV and retag it as a CX. This would explain why both master cylinders are stamped US.

Ed

How would they handle a JL8 replacement in the field? Would need some kind of work instructions for the dealers or P&A would have side note explaining the removal of the valves. I think the side note in the P&A would have been used as the parts person would pass the information to the mechanic.
No side notes in any of the P&A's, so must be another explanation or maybe that is the explanation.
Bob

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Re: JL8 master cylinder
« Reply #30 on: May 14, 2016, 05:45:51 PM »
Based on the procedure in the service manual I would guess when a US master cylinder was ordered, either for 2 or 4 wheel discs, it would be packaged with no residual valves (to be reused or ordered separately) and with new brass tube seats in the box. Anyone have a NOS master cylinder?
John
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bertfam

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Re: JL8 master cylinder
« Reply #31 on: May 14, 2016, 11:47:51 PM »
Quote
Based on the procedure in the service manual I would guess when a US master cylinder was ordered, either for 2 or 4 wheel discs, it would be packaged with no residual valves (to be reused or ordered separately) and with new brass tube seats in the box. Anyone have a NOS master cylinder?

I don't have an NOS master, but I HAVE purchased a few Chevrolet master cylinders in the past for Camaros I've owned over the years, and I don't remember them having to be "put together". In a service standpoint, the parts are usually "plug-n-play".

I'm not saying it's not possible, but I don't think it's probable. A better scenerio would be that you'd have to remove the RPV for JL8 if you got one from the dealer.

Ed

JKZ27

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Re: JL8 master cylinder
« Reply #32 on: May 15, 2016, 01:08:45 AM »
Yeah Ed, if you've bought a few in the past and don't remember any kind of assembly, I think I have to agree.
John
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KurtS

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Re: JL8 master cylinder
« Reply #33 on: May 15, 2016, 03:13:44 AM »
Sorry, I wasn't here lately. But you got to the most likely explanations. The assemblies were different.
But how the masters were handled in service is a major omission in the service documentation.
Kurt S
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big iron

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Re: JL8 master cylinder
« Reply #34 on: May 15, 2016, 02:33:47 PM »
As far as service, possibly with only 206 units in circulation, and using Ed's explanation as to why US was used on two different applications, it is likely that the problem never arose at the dealers.
With the vender making the required modification for the JL8 the information did not get into the P&A and a ( note ) was not added to remove the RPV's. Thus explaining the lack of information and confusion in the P&A's about the US application of the 309 MC.
Bob

bertfam

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Re: JL8 master cylinder
« Reply #35 on: May 15, 2016, 04:49:53 PM »
Quote
But how the masters were handled in service is a major omission in the service documentation.

Agreed. There SHOULD be a note in the P&A mentioning the differences in installation. Something like "Remove RPV before installing in JL8". The P&A is full of notes like this, but somehow this one got lost.

Ed



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Re: JL8 master cylinder
« Reply #36 on: May 15, 2016, 05:16:12 PM »
Not sure if I should chime in here as my knowledge of Camaros are limited, but those 206 cars you are talking about, are you referring to the non power brake cars with front disc brakes and drum rears?  If so mine is one of them.  I do not have the original master cylinder on it now but do have the old one I took off.  I do not believe it is original either but could find out what the numbers are off of them or codes? if needed.  67 RS?SS with 396 and auto trans.

1968RSZ28

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Re: JL8 master cylinder
« Reply #37 on: May 15, 2016, 06:09:02 PM »
Not sure if I should chime in here as my knowledge of Camaros are limited, but those 206 cars you are talking about, are you referring to the non power brake cars with front disc brakes and drum rears?

No Leon, the 206 cars are the 206 '69 Camaros sold with power assisted 4-wheel disc brakes (JL8) from the factory.

Paul

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Re: JL8 master cylinder
« Reply #38 on: May 15, 2016, 06:30:37 PM »
As far as service, possibly with only 206 units in circulation, and using Ed's explanation as to why US was used on two different applications, it is likely that the problem never arose at the dealers.
With the vender making the required modification for the JL8 the information did not get into the P&A and a ( note ) was not added to remove the RPV's. Thus explaining the lack of information and confusion in the P&A's about the US application of the 309 MC.
Bob

If there really was a difference between the JL8 US master and the regular disc/drum US master, then wouldn't it have made more sense for GM to use a Corvette disc master for the JL8 application?
1969 Z28 JL8 4 wheel disc brakes, #'s match - being restored

KurtS

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Re: JL8 master cylinder
« Reply #39 on: May 15, 2016, 07:20:32 PM »
If there really was a difference between the JL8 US master and the regular disc/drum US master, then wouldn't it have made more sense for GM to use a Corvette disc master for the JL8 application?
One would think. It would be a lot cleaner for service.

And it doesn't matter if there are only 206 cars, documentation has to address all production variants.
Kurt S
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Re: JL8 master cylinder
« Reply #40 on: May 15, 2016, 10:58:34 PM »
In the 1969 Chassis Service Manual, there is a chart listing the master cylinder codes and their usage. Here's a few;
Camaro and Nova with power disc.......US
Chevelle with power disc....................BA
Corvette with power disc....................PG
"The two-letter identification stamp on the end of the master cylinder indicates the displacement capabilities of that particular cylinder."
There are no special service procedures for the master cyl in the 4 wheel disc section as it simply refers you to the Duo-Servo Brakes section.

If the Chevelle/FS, Camaro/Chevy II and Corvette all shared the same casting master cylinder, would the "displacement capabilities" be differences in the internal chambers of the master or differences in the pumping displacement of the piston?
1969 Z28 JL8 4 wheel disc brakes, #'s match - being restored

big iron

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Re: JL8 master cylinder
« Reply #41 on: May 16, 2016, 03:21:40 PM »
In the 1969 Chassis Service Manual, there is a chart listing the master cylinder codes and their usage. Here's a few;
Camaro and Nova with power disc.......US
Chevelle with power disc....................BA
Corvette with power disc....................PG
"The two-letter identification stamp on the end of the master cylinder indicates the displacement capabilities of that particular cylinder."
There are no special service procedures for the master cyl in the 4 wheel disc section as it simply refers you to the Duo-Servo Brakes section.

If the Chevelle/FS, Camaro/Chevy II and Corvette all shared the same casting master cylinder, would the "displacement capabilities" be differences in the internal chambers of the master or differences in the pumping displacement of the piston?
Chevelle and Camaro used the same casting 309 with 11/8" bore and the replacement repair kit 5469406, ( All 69 with disc brakes at the time shown in 10.1.69 P&A ). Corvettes used the same 67 corvette casting and different part #5461184 shown in 1.1.73 Corvette P&A. Would need to verify with 67/68 P&A.
The 69 Camaro used the 309 casting for 2 different applications RPO J50/J52 disc/drum and RPO JL8 4 wheel disc and they both used the same 11/8" bore repair kit with the same pistons. I believe that the stampings are for applications not for displacement capacity.
I believe the service manual to be incorrect in the reason for the stampings.
Bob

big iron

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Re: JL8 master cylinder
« Reply #42 on: May 16, 2016, 04:02:27 PM »
If there really was a difference between the JL8 US master and the regular disc/drum US master, then wouldn't it have made more sense for GM to use a Corvette disc master for the JL8 application?
One would think. It would be a lot cleaner for service.

And it doesn't matter if there are only 206 cars, documentation has to address all production variants.
Kurts,
If you have original 69's with RPO 50/52 that have 309 MC's with US stampings and original 69"s with RPO JL8 that have 309 MC's with US stampings and they are documented as original , then would this not be documentation that there was a production variant??
Bob

KurtS

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Re: JL8 master cylinder
« Reply #43 on: May 16, 2016, 06:47:41 PM »
Variants = versions.
The fact that the RPO was produced makes it a variant.
Kurt S
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big iron

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Re: JL8 master cylinder
« Reply #44 on: May 17, 2016, 01:46:39 AM »
See you have updated the MC application code list.
Bob

KurtS

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Re: JL8 master cylinder
« Reply #45 on: May 17, 2016, 04:22:59 AM »
Actually, it was always US. Then when I asked the question I changed it to ??. I changed it back to US.
Kurt S
CRG

franzasport

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Re: JL8 master cylinder
« Reply #46 on: April 28, 2019, 01:43:18 PM »
Hello, I need some help please ..I am from France ...
I have a 69 camaro very special..its a survivor  she stop here life in 1973 and all the parts from now are still the same cause she was stopped in good condition ..unless :radiator missing , exhaust rusted ,and master cylinder out and tyres of course .
 see my website tuerlinxcamarol89 or franzasport.com on this car.
since I find it she do only 400 miles at this time for some raisons..
20 years ago I ll made a MASTER BIG mistake  I replace the original master cylinder by a standard 1.1/8 camaro disk brake the car have j56 calipers whith big 4 pots rear
I have a problemo its necessary to put to much pressure on the pedal to stop it and very very dificult to   block the wheels..like no depression in booster so my question is: the new j56 gm repro master cylinder can help me or not cause I have the same bore?
any sugestion welcome  to help to stop that beast...

Charley

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dannystarr

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Re: JL8 master cylinder
« Reply #48 on: April 28, 2019, 11:26:40 PM »
I believe there are some JL8 systems that included the #3908326 frame mounted hold back valve. I know of 3. One may have been modified, but the other two are almost for certain original. Danny