Author Topic: Where to by correct master cylinder?  (Read 19718 times)

69Z28-RS

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Re: Where to by correct master cylinder?
« Reply #15 on: November 11, 2016, 01:01:34 AM »
I could not find the RPVs either when I needed them in a replacement MC a few years back.  I had to buy one of the NAPA MC rebuild kits that John mentions above. So ~$30 for 2 little rubber valves(!) but I also used the brass ports from the kit too even though I didn't damage the old ones when I removed them.
...
Gary: The spring is only to hold the rubber valve against the back of the brass port. So, no valve, no spring. The springs are included in the NAPA rebuild kits.

Thanks!   I thought that was likely the case..  but nice to have it confirmed... :)
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67stripper

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Re: Where to by correct master cylinder?
« Reply #16 on: November 11, 2016, 10:44:36 PM »
I've also been struggling to find a good quality new or rebuilt master cylinder for my power brake 1967 Camaro. The car did not come originally with power brakes and I added a power booster and am looking for the correct power brake master cylinder with bleeders as shown in Pic1 - DrumBrakeBleederMC. I've been working on this off and on for about 20 years.

Here is my experience and problems.

First I must say that this is brakes. Safety is paramount. If you don't know what you are doing or don't feel comfortable working on master cylinders and brakes don't do it. You could kill yourself and or others.

With respect to residual pressure valves (RPV) attached are a couple of pictures.

Pic2 - 1143 - RPV assembly from a Fenco rebuilt unit purchased about 2000
Pic3 - 1220 - New GM RPV parts from my inventory purchased 1980s
Pic4 - 1221 - 1967 Camaro GM service manual master cylinder break down with my handwritten RPV part numbers

From GM RPV as shown in Pic2 are installed in both outlet ports of the master cylinder for drum brakes and only in the rear brake port for disk brakes. Residual pressure valves are required for proper operation of the stock GM cylinders and brakes as outlined in many GM service publications. The RPV are used to keep the brake shoes close to the drums so brake action is quick. The system will work without them but you may have to pump the brakes a couple of times during operation to get adequate braking. Not the best and potentially unsafe. I know of no source for the RPV parts other than to buy them from GM (likely long discontinued) or via NAPA or Raybestos master cylinder rebuild kits. The current  Raybestos kit comes with a nice fine thread screw that you can use with a couple of washers to put out the brass seats. Unfortunately expensive. You may be able to buy the parts from master cylinder rebuilders but I've never tried this route as my local parts supplier stocks the rebuild kits and it is easy.

When I started looking for a master cylinder for my Camaro I could not find a new one that had RPV. There are others posts on this forum detailing the same problems. I ordered cylinders from all of the major suppliers and found that they all looked exactly the same and appeared to be from the same manufacturer. No RPV but did have the brass insert seats for the ports so a RPV could be installed if the casting was machined or cast for them. None of these master cylinders had bleeders. So, i ordered a Fenco rebuilt unit without bleeders and it had RPV. I installed this unit but did not drive the car other than around the yard and as a result had no real experience with the operation of it. This was about 15 years ago.

Just this year I started working on the Camaro again and took the Fenco rebuilt unit apart to install a new kit. What a mess. This unit was absolute junk and it is a good thing I never drove the car with it. The cylinder appeared to be sleeved with some material that appeared to be stainless but it was corroded beyond use. Not really bad but unusable. When sleeved the sleeve was not drilled for the stop bolt (it was not installed) and the front RPV was sucked into the port and the spring was pushed through the end of the rubber valve damaging it so it would not work. You can see this in the top valve in Pic 2. The rear port hole in the sleeve was offset and I don't think much fluid would get through it. So, if you are going to buy a rebuilt unit beware and take it apart to make sure it is done properly. There are some real horror stories about rebuilt and resleeved master and wheel cylinders even from supposedly reputable firms in business for a long time.

If you have your cylinder resleeved there are choices of material for the sleeve including various types of stainless and brass. Stainless lasts longer but some types corrode more than others. Stainless does corrode with time. Brass corrodes less but is not as durable. Each type of sleeve seems to have those who like it better. My feeling is that if you are going to use your car a lot then use stainless but make sure it is seamless. There have been reports in this forum of major suppliers using seamed material. This does not work and is dangerous.

From what I have been able to determine the only cars that came with bleeders on the master cylinders are Camaro power brake cars. With power brakes the booster is offset so the master cylinder is mounted on an incline with the front of the cylinder up. The bleeders are required to bleed air from the system on the assembly line as I believe they do not bench bleed the cylinders. I believe that all other GM cars do not have this inclined design and as such no other master cylinder except a Camaro power brake cylinder will look correct  or really work well. You can bench bleed a cylinder without bleeders and install it but if you loose fluid in the cylinder for any reason including service repairs you need to do this again. My experience is that it is nasty to bleed a system without bleeders and worse if you use DOT 5 silicone fluid as it has an affinity for air.

To make the Camaro drivable this time I purchased a new Raybestos cylinder MC36239 for a 1967 Chevrolet. MC36233 if the listing for a Camaro but it has a Chrysler type top which for correct appearance I did not want to use. MC36239 is made in China and does not have RPV or brass inserts in the outlet ports and it does not have a stop bolt. The outlet ports have cast bosses for the brake line sealing so you can not put RPV in these cylinders. I expect this is done to save costs. I have not tested this cylinder other than to drive from the trailer on the street to my shop at the back of my property. It seemed to stop okay but I'm still looking for a good new proper master cylinder or a good core. I've looked for a long time and never found a good used bleeder type core for drum brakes. I do have two disk brake ones so maybe I'll just convert to disk brakes.

If you are in a real bind you can install after market RPV available from a number of sources. These are typically 2# units threaded on each end so you can cut your lines and install them where needed. I may do this. I've used these on race cars and they work very well.

I have no experience with the currently available new disk brake reproduction cylinders from a number of sources. However, based on my experience over the years I'd say they are all likely made by the same source, likely in China, and should be checked for proper parts and operation before installation. I guess we just have to put up with this stuff for 50 year old cars.

My last comment is don't go cheap. This is brakes and safety. Buy good stuff. Take the time to do your homework and make sure what you are doing is correct and will work properly.

I've researched this quite a bit so if anyone has questions please feel free to ask and I'll try and help. If you have a good bleeder drum brake core please contact me. Even better is NOS.

TRLAND

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Mike in Northern Illinois
1967 RS 327

67stripper

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Re: Where to by correct master cylinder?
« Reply #18 on: November 12, 2016, 05:10:20 PM »
Thanks. Appreciate your help.

DAVEN1256

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Re: Where to by correct master cylinder?
« Reply #19 on: November 14, 2016, 02:21:06 AM »
I'm glad all of this came up about the RPV because I had no idea they even existed. It's always good to learn something new.

That got me curious about the master cylinder I am replacing. It is a parts store replacement that I bought 15 to 20 years ago. I pulled the brass seats out of the ports and guess what? NO RPV in there for the rear brakes !!! It looks like a rebuilt Delco unit with the casting number 5468115.

From the time I put this master cylinder in (and before) to the time I started taking the car apart in 2008, the car only got driven every couple of weeks and only few miles each time just to keep it in running shape. The brakes during that time were terrible. Maybe that was part of the reason why.

So now I am wondering, should all master cylinders from any of the parts houses that are specifically for a Camaro with disc brakes have the RPV for the rear brakes? Not finding one in the master cylinder doesn't give me a lot of confidence.


Thanks.....Dave






bertfam

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Re: Where to by correct master cylinder?
« Reply #20 on: November 14, 2016, 02:34:43 AM »
I can't comment on 3rd party rebuilt master cylinders, especially one that isn't a correct casting number for the first generation Camaro, but all ORIGINAL Camaro drum/drum brake masters have a RPV in both ports, and all ORIGINAL disc/drum masters have a RPV in the rear port.

Is there a two letter code stamped on the front pad of your master?

Ed

DAVEN1256

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Re: Where to by correct master cylinder?
« Reply #21 on: November 14, 2016, 03:02:03 AM »
There is no two letter code stamped.

I am just wondering now if you order a Camaro specific MC, can you expect the RPV to be there? Or do you have to pull the brass seat to be sure?....Which I would hate to do on a brand new unit.

I mean the ones you order from HBC, Right Stuff, or any of the Camaro parts catalogs.

Dave

TRLAND

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Re: Where to by correct master cylinder?
« Reply #22 on: November 14, 2016, 05:46:13 AM »
There is no two letter code stamped.

I am just wondering now if you order a Camaro specific MC, can you expect the RPV to be there? Or do you have to pull the brass seat to be sure?....Which I would hate to do on a brand new unit.

I mean the ones you order from HBC, Right Stuff, or any of the Camaro parts catalogs.

Dave

I would not expect ANY Camaro parts suppliers to sell a new or rebuilt MC with RPVs.  I went through 3 of them sending them back after checking and was told either they weren't necessary or that they had no idea what I was talking about.  I even sent one of the above vendors the picture and link to JohnZ's report from this site to show them what they are and why they're necessary in a drum brake application and they still wouldn't admit I needed them.

You can check if they're there without pulling the brass seat by lightly putting a blunt probe into the port to feel for resistance.
Mike in Northern Illinois
1967 RS 327

69Z28-RS

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Re: Where to by correct master cylinder?
« Reply #23 on: November 14, 2016, 01:21:00 PM »
Most of the aftermarket brake suppliers nowadays sell their systems with what they call a 'combination' valve; which seems to incorporate all the necessary functions.  As JohnZ states in his brake report:

"Combination Valve
Although not used on any first-generation Camaro, all of the separate distribution/valving functions described above (distribution block and warning switch, metering/hold-off, and rear proportioning) were integrated in later second-generation disc/drum cars into what became known as the "combination valve". This valve, usually machined from brass, combined all those functions in one single device, which simplified packaging and plumbing. Multiple part numbers were required to accommodate calibrations for differing vehicle weights and configurations."


I'm wondering if perhaps the Combination Valves nowadays also incorporate the RPV...?  After all they do incorporate the proportioning valve, which is only necessary where mixed 'disk/drum' brake systems are incorporated, so maybe the same thing is true with the RPV??   Does anyone know if this might be true?
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z28z11

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Re: Where to by correct master cylinder?
« Reply #24 on: November 15, 2016, 01:14:32 AM »
OK, you got me to thinking about my 346 Fenco rebuilt MC, so I decided to haul it out and check. No sign of RPV's in either port, although seats are new. Considering what was posted about rebuilt units, I've decided to pull this one apart before I install it and check it out. Fortunately, I put the original Delco rebuild kits away years ago for just this instance, both the '68 and '69 kits. This MC, by the way, IS marked WT (faint, but you can see it under magnification. I suppose the paint is pretty deep, or it was blasted heavily. Otherwise, overall, it's not bad).

One of the reasons I mention the difference in the kits concerns the pic of the recess on the piston assembly. Be aware that there is a difference in depths from '68 to '69 for the actuating rod from the power brake booster - length of the rods are different. Piston bores are, too - I believe the '68 is the 1.00" bore diameter, while the '69 is 1.125". Somebody feel free to correct me if I err -

Regards,
Steve
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z28z11

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Re: Where to by correct master cylinder?
« Reply #25 on: November 15, 2016, 01:15:35 AM »
Pics 3 and 4 -
1968 Z28 M21/U17 BRG/W 1967 Chevy ll Nova SS 
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06  1949 3100 5wd 235/6

bertfam

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Re: Where to by correct master cylinder?
« Reply #26 on: November 15, 2016, 01:48:36 AM »
Quote
I believe the '68 is the 1.00" bore diameter, while the '69 is 1.125". Somebody feel free to correct me if I err.

Steve, all Power disc master cylinders are 1.125" bore and all drum brakes and 1967 manual disc are 1" bore (except 1967 manual J65 drums, which is 7/8" bore). See the MASTER CYLINDER CODES TABLE for more info.

I'm really surprised at the master cylinders NOT having the RPV! Especially your WT master. I can't imagine why. They're needed to keep the rear drum wheel cylinders expanded a bit so when you press the brake pedal, it doesn't go all the way to the floor!!

Ed

z28z11

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Re: Where to by correct master cylinder?
« Reply #27 on: November 15, 2016, 02:22:12 AM »
The mention before about missing RPV's on rebuilt masters is why I decided to check it. Glad I did -

I agree with the 1.125 bore statement - memory lapse on my part (that's why I asked to be corrected !). Next time I'll research before I leap - thanks !

Regards,
Steve
1968 Z28 M21/U17 BRG/W 1967 Chevy ll Nova SS 
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06  1949 3100 5wd 235/6

Steve68

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Re: Where to by correct master cylinder?
« Reply #28 on: November 15, 2016, 03:00:09 AM »
The lack of RPV's in aftermarket cylinders was discussed in the following thread in 2007.  http://www.camaros.org/forum/index.php?topic=2938.msg18849#msg18849

Steve

69Z28-RS

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Re: Where to by correct master cylinder?
« Reply #29 on: November 15, 2016, 05:22:40 AM »
Steve,  your 2007 story sorta confirms what people are seeing TODAY, so apparently the suppliers have not corrected that problem (Omission of RPV valves)...  I still think it's possible that they believe it's corrected in the 'combination valve'...??
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69 Corvette, '60 Corvette, '72 Corvette
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72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan

 

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