67 pb master cylinder

[Tom Reppart]

I have a 67 small block, non-power brakes coupe. I'm planning to add the J50 power brakes. I'm really confused about whether I need to change out my master cylinder. The NCRS tech manual say's that standard and J50 power brakes us a 545509 master cylinder (which I have), while the J56 option uses a 548346. However, half the restoration books and catalogs have conflicting information on whether J50 uses a "509" or "346" master cylinder. I'd like to think the NCRS book is right, but some other reputable restoration guides say otherwise.

Can someone look under the hood and tell me which master cylinder I'm supposed to use ???

Confused, and trying not to get frustrated...

Tom

[Joe L.]

Re: 67 pb master cylinder

Tom-----

There is a lot of "conflicting" information out there on this one. However, the real deal is that all 1967 Corvettes EXCEPT those equipped with J-56 HD brakes used a 1" bore master cylinder of GM casting #5455509 with a broadcast code of "DC". This was stamped onto the half-moon-shaped machined area on the front of the master cylinder. The '509' master cylinder was used for BOTH standard brakes as well J-50 power brakes. 1967 Corvettes with J-56 HD power brakes used a 1-1/8" bore master cylinder of GM casting #5480346 and a broadcast code of "PG".

Partly what confuses this matter is that after 1967, beginning with the 1968 model year, the '509' master cylinder was used only for manual brake applications and the '346' was used for all power brake applications, including both J-50 as well as J-56. But, for 67 the usage was as I described above. Absolutely. Positively.

[Gerry Proctor]

So, Joe how muddy are these waters?

Joe,

I recently acquired a 5460346 cylinder with a PG broadcast code. Even though I have a non-power brake '72 I couldn't pass up this cylinder since it had recently been brass-sleeved and the price was right. I know that it has an application for the 67-69 Z/28 and has some Corvette application, but I'm not absolutely certain which. Now here's where the waters get muddy (for me, anyway) for this cylinder... I've generally observed that non-assist cars use a deep-well piston for the push rod and that assisted brake cars use the shallow-well piston. This 5460346 cylinder has a deep-well piston for its 1.125" bore which prompted me to further researh this. This lead me to a discovery that you can purchase piston kits for both 1" and 1.125" cylinder bores with either the deep or shallow piston which only made things more muddy. Any idea on the application and piston well situation? Thanks ahead.
Gerry

[Tom Reppart]

Re: 67 pb master cylinder - Thanks

Thanks Joe -
As always, I knew I could find the right answer on the NCRS discussion board. I should have saved the money I spent on books :o)

Tom

[Joe L.]

Re: So, Joe how muddy are these waters?

Gerry-----

The GM casting #5460346 casting with a "PG" broadcast code was used for 1967 Corvettes with J-56. It was also used for 68+ Corvettes with J-50 or J-56 power brakes. At the moment, I don't know when this casting ceased to be used for Corvettes, but I know that it was used well into the mid-to-late 70s. Examples used in PRODUCTION and supplied for SERVICE after about 1973 no longer were machined for bleeder valves, though. Some SERVICE and, possibly, PRODUCTION examples of the master cylinder may have code "BA" stamped on them rather than "PG".

As far as other non-Corvette applications, the only one that I know of is the 1969 Camaro Z-28 with the JL-9 four wheel disc brake option. This set-up used the Corvette 4 piston calipers at all 4 wheels and was very similar to the Corvette braking system.

However, this does not mean that all GM casting #5460346 are "created equal", so to speak or were used only on the above-referenced Corvette and Camaro applications. This particular casting was used on a wide array of 1-1/8" bore master cylinder applications in the 67-76 period across the Chevrolet (and probably other GM) car lines. The internal configurations of those master cylinders differred depending upon the application that they were designed for. This likely included, as one element, the differences in the pistons that you described.

I can tell you that the 5460346 casting master cylinders used for Corvettes were all configured internally the same. For example, the master cylinders bearing this casting number and used for 1967 Corvettes with manual or J-50 power brakes were the same. Also, the master cylinders bearing this casting number for 68+ were the same as those used for 67 applications.

[Gerry Proctor]

Re: So, Joe how muddy are these waters?

Thanks much, Joe. The cylinder has bleeder screws so I at least already knew that it's application didn't occur after 1972. I guess until they develop genetic coding for parts I'll never know absolutely for certain what car this cylinder was born with.

Just looking for your opinion here if you want to weigh-in. I'm fully aware of why non-power brake cars use the 1" bore (smaller bore = less pedal pressure for adequate line pressure since it's a psi issue) and why power cars use the 1.125" bore. I was pondering installing this on my non-power '72 and doing a field test for adequacy. I currently have a Wagner cylinder on it and wanted to have the correct "appearing" cylinder even if it's not the correct part number. I'll never have the car judged, but it's just one of those nagging things because I know what it's SUPPOSED to look like under the hood. It sure looks pretty sitting on my parts shelf, but... Any experience, heresay or otherwise, on why I shouldn't perform this experiment?
Again thanks and regards,
Gerry

[Joe L.]

Re: So, Joe how muddy are these waters?

Gerry------

I've talked to several folks that have installed the 1-1/8" bore master cylinders on manual brake cars. They thought that it would "improve" braking performance. Every one reported that they couldn't tell any difference, though. I usually tell them that's good because if they had noticed a difference, I doubt that it would have been the kind of difference they sought. In any event, I think that you could use the master cylinder without creating braking problems. However, correct '509', "DC"-coded master cylinder castings aren't really too hard to come by.

As far as on what vehicle that your master cylinder was originally installed, we pretty much know that it was a 67-73 Corvette or 1969 JL-9 Camaro. No other applications used the "PG" coded cylinders as far as I know. Furthermore, we know that the number of 1967 J-56 cars was very small (267) and the number of JL-9 Camaros also very small (less than 200, as I recall). So, it's VERY doubtful that it ever resided on either of those 2 applications. That leaves 68-73 Corvettes with J-50 or J-56 power brakes.

Now, if you look at the machined boss for the forward brake line fitting, you should see a very small, light stamping. This will provide the Julian date code that the cylinder was manufactured. That should narrow down where it originally resided even further. Of course, it could also have been a SERVICE master cylinder produced during the 67-73 period, so it's possible that it never passed through St. Louis, at all.

If you really want to go further and try to identify the VIN number of the car that it was originally installed on, assuming that it was originally installed in PRODUCTION, I'm afraid that I won't be able to help. Perhaps someone else will, though.

[Gerry Proctor]

Thank you again, Joe.

For realistically narrowing it down for me. I'll continue to somewhat passively search out the 509/DC casting.
My expectation was that installing the cylinder would likely do little more than allow me to add muscle mass to my thighs from the increase in pedal effort. I'll put that to the test since I guess the only thing I have to loose is having bleeding the system -and we all know how much fun that is ;-).

[John H.]

Re: So, Joe how muddy are these waters?

Joe -

All 1969 Camaro SS, Z/28, and 427 COPOs with either J52 power disc/drum brakes or JL8 4-wheel discs used #5468309 (with broadcast code "US", indicating 1.125" bore, bleeders, and short-hole rear piston) as the production part; the JL8 installation differed only by not having the (external) low-pressure metering valve in the front pipe between the master cylinder and the distribution block/differential pressure switch. I expect the 5460346 was specified as a service replacement when the 5468309 was no longer available.

[Joe L.]

Re: So, Joe how muddy are these waters?

John-----

So, that narrows the list of cars originally using the '346', "PG"-coded master cylinder even more; I thought that they had been used on the 1969 Camaro 4 wheel disc brake applications.

As far as the '309' master cylinder goes, I have heard that they were also used on some 68-72 Corvette with J-50, but I don't think that I've ever actually seen one in such an application.

I wonder what the difference was between the '346' and '309' castings other than, obviously, the casting number?

[John H.]

Re: So, Joe how muddy are these waters?

Joe -

Would be interesting to compare them side-by-side and find out. Buick was the GM "lead division" for brake systems in those days, and must have driven Delco-Moraine bananas with all the master cylinders they released in the 60's and 70's. There was a lot of "Not Invented Here" pride at each of the Car Divisions as well - God forbid that a Chevrolet brake engineer should release the same master cylinder for his application that would be shared with another Division (with the same application); his was naturally "better" (and cheaper)

[Brian M.]

So what should I expect to pay for a

5455509 core or sleeved master?

[Joe L.]

Re: So what should I expect to pay for a

Brian-----

For a core, about $50-100. For an outright, sleeved unit ready to bolt on about $300-350. You might be able to find cores for less at swap meets (but likely not Corvette-oriented swap meets). I once purchased a '509' core at the Pomona, CA swap meet for $5. That's also what the guy was asking for it. I didn't bother to argue with him, at all. Just wouldn't be fair.

[Brian M.]

Thanks Joe... *NM*