'63 Master Cylinder

**Joe L.** · August 20, 2002, 10:01 PM

Re: '63 Master Cylinder

Rich-----

I have no record of this master cylinder casting number ever being used on a Corvette. Also, I can't find any reference as to what this particular casting was used on. However, many of the 62-65 passenger car master cylinders were Moraine-built units with a 1" bore diameter. I strongly suspect that's what you have.

One other piece of information: with rare exception, master cylinder castings were specific to a certain bore diameter. In other words, a single casting (and casting number) was not used for master cylinders of different bore diameters. A single casting MAY have been used for several different finished master cylinder part numbers, but not master cylinders of different bore diameters.

**Geoff C.** · August 21, 2002, 01:12 AM

1" is Passenger car; 7/8" is Vette *NM*

**Verne Frantz** · August 21, 2002, 11:21 AM

Re: '63 Master Cylinder

Rich,
That casting number is indeed for a '62 or '63 passenger car with power brakes, w/o the metallic brake option. It is always a 1" bore. The lid is the same as the Vette, except the Vette used a hex head screw, where the passenger application used a thumb screw.
The metallic brake option master for passenger cars used a 7/8" bore, but the casting was different than for the Vette. There are many Corvette parts which are the same as passenger cars, but the master is not one of them.
Verne.

**Duke W.** · August 21, 2002, 12:36 PM

Re: '63 Master Cylinder

I think Vern has is right. According to GM's specifications. The base brake package used a 1" M/C, but the J-65 metallic brake option incorporated a 7/8" master cylinder.

I always figured these were the same castings - just finished bored to the two different dimensions, but if Joe is correct that each finished bore size used a different casting, that would mean that base and J-65s are different castings and I don't this is reflected in the 63-64 JG.

Comments?

Duke

**Joe L.** · August 21, 2002, 03:45 PM

Re: '63 Master Cylinder

Duke-----

I'm not sure if you're talking about passenger cars, Corvettes, or both. In any event, as far as Corvettes go for 1963 and 1964, standard brakes, J-50 power brakes, or J-65 metallic brakes all used the same 7/8" bore master cylinder of Moraine manufacture. 1963 ZO-6 and 1964 with J-56 used a different master cylinder which was of Kelsey-Hayes manufacture. At the moment, I'm not sure of the bore size of this master cylinder. It's a very "rare bird", anyway.

For passenger cars of the 62-65 period, many master cylinders were of 1" bore, as I described earlier. There may also have been 7/8" bore passenger car master cylinders. I don't have the specifics at the moment, though.

**Verne Frantz** · August 21, 2002, 04:30 PM

Re: '63 Master Cylinder

Joe,
I thought I was pretty clear on the passenger car masters in my earlier post. 1962 & 1963 passenger cars with the metallic brake option got a 7/8" bore master. Each of those (pass.) years was a completely different casting for the 7/8". ('62 was different from '63). The non-metallic masters, which were 1" bore, were one casting for non-power brakes for '62 & '63 pass, and one casting for power brakes for '62 & '63 pass. Prior to '62 and after '63, passenger cars with metallic brakes had a 1" bore master, and only one type was offered each year, regardless of brake options.
regards,
Verne.

**Duke W.** · August 21, 2002, 05:18 PM

Re: '63 Master Cylinder

The base/J-65 master cylinder has always been mysterious.

The '63 Corvette shop manual specifies the base brake master cylinder as having a 1" diameter and 7/8" with J-65 metallic brakes. The AMA specifications list a 1" bore for base brake master cylinders, but no mention is made of master cylinder bore in the supplementary page for J-65.

My AIM mentions ABSOLUTELY NOTHING about J-65 brakes. There is no mention of them in the suspension or brake sections nor does my AIM have a J-65 section.

Installation of J-65s would have involved the same procedures as base brakes except differnent front knuckle and rear trailing arm assemblies would have been required along with the J-65 specific master cylinder, but I can find nothing my AIM to indicate different part numbers for J-65 optioned cars.

A smaller bore for J-65 makes technical sense given the metallic linings lower friction coefficient under normal driving conditions. A smaller bore will generate more line pressure for a given pedal effort at the cost of increased travel.

I consider the base/J-65 master cylinder bore diameter to be an unresolved issue. The two sides of the story must be reconciled some day.

Duke

**DANNY PANTUSO** · August 21, 2002, 10:36 PM

Re: '63 Master Cylinder *NM*

P>

**andy#34338** · August 22, 2002, 07:05 AM

Re: '63 Master Cylinder

I will have a nice 1" bore at the Carlisle MAC tent if someone want to compair them.

Andy

**Joe L.** · August 22, 2002, 11:22 AM

Re: '63 Master Cylinder

Duke-----

I think that I can shed some light on this issue and, perhaps, reconcile some of the 1963 master cylinder issues.

For 1963 PRODUCTION, the master cylinder specified was GM #3814890 or, alternately, GM #5462385. This is further subtantiated in the 1963 AIM. GM #3814890 was a Kelsey-Hayes-manufactured master cylinder. It is the master cylinder which was configured more-or-less as depicted in the AIM drawing. I don't think that this master cylinder was ever used in PRODUCTION; at least, I've never seen one on or off a car. As far as I can tell, it was never available in SERVICE, either.

I believe that the master cylinder used for most 1963 Corvette applications was the GM #5462385 master cylinder. This is a Moraine-manufactured unit with a 7/8" bore diameter and utilizing the 5462389 casting. The GM #5462385 master cylinder was available in SERVICE and is specified in 1963 SERVICE parts information as applicable to all 1963 Corvettes except "special performance". With respect to 1963 Corvettes, the term "special performance" denotes the RPO ZO-6 option.

For 1963 Corvettes with "special performance" (RPO ZO-6), the master cylinder used was GM #3828760. This is a Kelsey-Hayes manufactured master cylinder of dual piston design (the first ever used on a PRODUCTION Corvette). I do not know the piston diameter of this unit, though.

For 1964, most Corvettes were built using the GM #5464435 master cylinder. This master cylinder is also of Moraine manufacture, of 7/8" bore diameter, and utilizes the 5462389 casting. In SERVICE, it was known as GM #5464275 (likely as a result of other parts being supplied with the unit). When SERVICE stocks of the 63 GM #5462385 master cylinder were exhausted, this unit became the SERVICE master cylinder for 1963 and 1964 applications. I do not know how the 1963 and 1964 master cylinders differ, but I expect that it is in some minor way. The castings and the finished bore diameter for both years are the same.

For 1964 with "H.D. brakes", the same GM #3828760 Kelsey-Hayes master cylinder as used for 1963 "special performance" (RPO ZO-6)was used. With respect to 1964 Corvettes, the term "H.D. brakes" denotes RPO J-56. For 1964, since RPO ZO-6 was no longer available, the heavy duty brakes which that package included were offerred as a seperate option.

From what I can tell, and going right back to 1963-published GM information, the above-referenced master cylinders were the only ones available from GM in SERVICE. Also, they were the only ones that SERVICE parts (e.g. rebuild kits, gaskets, covers, etc.) were available for. If any other master cylinder was ever originally used in PRODUCTION for 1963 (or 1964) Corvettes, for example as part of the J-50 or J-65 brake systems, then that/those master cylinder(s) were NEVER available from GM in SERVICE. In addition, no parts to SERVICE any other possible 1963-64 master cylinder(s) were ever available in SERVICE from GM.