JL8 master cylinder

[JKZ27]

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?

[bertfam]

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]

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.

[KurtS]

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.

[big iron]

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]

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

[Leon in Mn.]

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]

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

[JL8Jeff]

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?

[KurtS]

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.

[JL8Jeff]

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?

[big iron]

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]

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]

Variants = versions.
The fact that the RPO was produced makes it a variant.

[big iron]

See you have updated the MC application code list.
Bob