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Well clearly the deeper strike of the "O" and other numbers vs the depth of the "M" looks a little odd.

Richard

Uh-oh!

Richard

Enjoy the car as it is..........

......... don't let it [finding the whole story] consume you.

Exactly why I am so glad my '69 RS isn't anything special.  Not worried about originality, value, or over thinking it - just get to enjoy driving a very nice ride.

Richard

Norwood, O1C, RS

Stamped numbers on end of motor:  5045605, Type E, 12v
Stamped wording on side of motor:  Delco Products, Rochester N.Y. USA  (Couldn't get a very good picture - brake booster is in the way - but you can make out "N.Y. USA" at the end of the stamping.

Richard

["GM documentation confirms that drum brake master cylinders are BS code and most drum brake master cylinders are coded BS. But a limited number have been observed with the CT code, in both manual and power drum applications. The CT code was used on drum brake applications on Pontiac and Buick vehicles. It is presumed that the CT part was used as a substitute during a parts shortage that and the differences between the BS and CT master cylinders are minor."]

Different master cylinders were used for Camaros with manual and power drum brakes per CRG as there were bleed valves used on the master cylinder for power drum brakes:

http://www.camaros.org/suspen.shtml#Brakecomp

Yes, power assist master cylinders are mounted at an angle with trapped air pockets necessitating the need for bleed valves - but all drum brake master cylinders be they manual or power assist have residual pressure valves.

An interesting sidebar point from CRG report......power assist drum brake master cylinder is "usually" stamped BS, however...... 

"GM documentation confirms that drum brake master cylinders are BS code and most drum brake master cylinders are coded BS. But a limited number have been observed with the CT code, in both manual and power drum applications. The CT code was used on drum brake applications on Pontiac and Buick vehicles.  It is presumed that the CT part was used as a substitute during a parts shortage that and the differences between the BS and CT master cylinders are minor."

The power assist drum brake master cylinder in my '69 RS (Norwood 01C) is a "CT" stamped master cylinder. 

Richard

Richard, so what does a factory residual pressure valve look like?  I pulled the brass seat out of an old drum master cyl (rear port) and there was nothing there!  Now I am confused.

The residual pressure valve & spring should be behind the seat.  Refer to the green highlighted text in the 1st & 2nd attachments and middle picture, left column, 2nd attachment.  When you pulled the seat out, it should have been there.

"Another variable at the master cylinder outlets is the use of check valves. They are installed under the tube seats in outlets which are to be connected to drum brakes. The retractor springs in drum brakes tend to force the fluid back into the master cylinder. The function of the check valves is to maintain a line pressure of 8 to 16 psi to keep drum brakes ready for quick responses."

Also refer to:

http://www.camaros.org/brakevalve.shtml#rpv



A general FYI - if you ever find yourself in the need of a replacement MC and you try to source one from any parts source - the residual pressure valves may not be there and the folks at the parts house probably won't know if you ask.  Consequently, my suggestion would be to rebuild a correct MC as opposed to trying to replace it.  Rebuilding it is not difficult at all to do.

Richard

I have two candidates (after I found my bracket).

I skinny one and larger one.  Which is more correct? Thx

My ride has the base 327/210 hp engine which has the small (1-1/4") bore Rochester 2GV 2 Bbl.  The return spring on mine is more like the "skinny" one you show.

Richard

I added the power MC/booster for safety. Still does not stop as well as discs.  Oh well.

The drums new are 9.5" inside diameter with a discard diameter of 9.560".  (Some sources say 9.590".)

For the drums to work effectively and as designed it is absolutely necessary that you:

•  don't exceed the 9.560" allowable inside diameter (so that the shoes don't have to move excessively

•  on the front brakes - install the larger (longer and somewhat wider) shoe to the rear and the smaller shoe to the front

• ensure that you have the correct residual pressure valves in the master cylinder outlet ports.

Richard

Instrument Services - in business since around 1979. 

They just finished the clock for my '66 Chevelle and did a quality job. Took about a month to get it back.

https://www.clocksandgauges.com/

Richard

PIE!

P=I*E

Power Equals Amps times Voltage.

SO They wanted to make Dang Sure you had a Good strong-Stable 12+VDC supply; as Voltage Droops Amps increase to maintain the same "Power consumption", So YOU Could Over amp the item on a Bench test when NOT complying with the Vendors instructions. The Better option to bench test is to use a "Current Limiting D.C. Power supply" that Most Hobbyist lack.

Sorry, this is my

W-A-G

Jim

Thanks Jim,


Something to consider.


Richard

The battery you used to bench test the clock was more than sufficient as a power source.

Thanks Mark,

My thought exactly.

Their insistence on having to use a car battery in order to properly bench test this clock makes no sense to me - especially given that the statement comes from knowledgeable folks that have been in the business for 46 years.

I'd be lying if I said that their statement didn't send up some red flags for me.

[CAR BATTERY]

Although, not a Camaro topic, this is related to our Camaros in a general sense.

The following involves the dash clock in my '66 Chevelle Malibu and the fact that my knowledge of the electrical side of things is not my strong suit.  A little background....

Originally, the clock in my Chevelle had an auto-wind mechanical movement manufactured by Westclocx.  It had constant +12v dc connected to it to provide power to the coils that were part of the auto-wind function.

The clock quit working a long time ago and in 2000, while I had the dash completely disassembled, I removed the clock from the instrument cluster and sent it to a vendor to be converted to a quartz movement.  Afterwards, the clock worked well until about 5 years ago when the hour hand quit moving.

This past December I began a series of "punch list" items on the Chevelle which included removing the A/C Heater control unit, cleaning and upgrading the slide levers from the original pot metal to stamped steel levers, lubricating the Bowden cables, etc.  With the AC/Heater control unit out of the way I also now had additional access to remove the clock for servicing.

In early December 2025, I shipped the clock to a well-known auto instrument servicing/repair company in the Rockford, IL area.  It was returned to me mid-January with instructions to bench test the clock prior to reinstalling and to ensure that the +12v DC power supply to the clock has a 1-amp fuse in the circuit.  I had planned on bench testing anyway and so far, so good.

The clock ran on the bench for 3 days without issue.  I then reinstalled the clock  in the car, and it ran for approximately 7 hours before stopping.  Go figure.  I tapped the back of the clock, and it ran again for a few minutes and then stopped.  I called the repair shop, explained the situation and even sent them a short video showing the clock running after being reinstalled in the car.  I also told them that I had bench tested the clock for 3 days prior to reinstalling it in the car using the 12v DC battery shown in the attached picture.  They said for me to send the clock back to them, which I did.  I just received it back on 15 Jan.  It currently is being tested, connected to its constant +12v DC power source in the car, prior to to re-installing it in the dash sometime next week.

It was extremely difficult to get any meaningful response from the vendor after I sent the clock back to them.  For example, when questioned as to what was wrong with the clock, all I got back was "the gears needed adjusting" which didn't tell me very much.
 
Now, here is where my confusion begins.........

After I told the vendor that I had bench tested the clock for 3 days prior to reinstalling it in the car using a Duracell 12v DC battery, the vendor responded, " IF YOU TEST THE CLOCK OUTSIDE OF THE CAR, PLEASE BE SURE TO USE A 12V CAR BATTERY PER OUR TECHNICIANS".   I asked for clarification and the response was that it is due to the "battery's capacity" and that "in the past they had had a clock stop during a bench test when using something other than a car battery".

My confusion is that in my mind, this quartz clock looks out to the world through its +12v DC and case ground connections and asks for ANY +12v DC source that can supply something on the order of 200 mA to the clock.  (I'm not sure exactly what the milliamp draw is, but remember, this is a 1 amp fused power supply, and I would be surprised if the current draw is much more than 200 mA).

Any ideas why the vendor would insist on using a car battery to bench test the clock and reference the capacity of the battery as being the reason?

The vendor is a very reputable provider of repair services for automotive clock, speedometer, tachometer, fuel gauges, oil gauges, battery gauges, amp gauges, temperature gauges, gas tank sending, etc. and has been around since 1979 with a significant business presence.  They are not a mom-and-pop garage operation.

Consequently, I must be missing something, but I can't figure out what. 

Any and all feedback would be appreciated.

It's a nice car and the owner loves it.

Can't go wrong with Glacier Blue.

Richard

I'd start by checking ground issues for #3 & 4.

Link beliw has installation instructions for the gauges.

http://www.camaros.org/forum/index.php?topic=19153.msg173331#msg173331


If you simply do a search (box - top right corner) for gauges or HEI, you will get many posts you can check.

Richard

Very nice indeed!

Richard