Where to by correct master cylinder?

[DAVEN1256]

I want to buy a new master cylinder for my '68. I have power front disc brakes. My original master cylinder is long gone. I would like to have one with the correct casting number and definitely the double bleeder valves on it.

The correct casting number for my car would be 5460364. I have looked at online at every company I know to look at and the only one is see who has that is HBC for $195. There are several companies that offer one with the casting number 5468309 which is correct for '69.....with prices ranging from $60 to $104.

First off, I can't see my way clear to pay almost $200 for a master cylinder so three questions.

Does anyone know of a cheaper source for a 5460346 master cylinder?

If I go for the cheaper incorrect 5468309, is there a difference in quality between suppliers. I don't know if there are many different manufacturers or if maybe every supplier gets theirs from the same one.

Are there noticeable physical differences between the 5460346 and 5468309?

Thanks.....Dave

[ko-lek-tor]

Advance Autoparts and maybe others (national chains), have rebuilt ones for $20-25. I'll check the one I have again just to be sure. It's laying on the floor over in the corner of the shop. Pretty sure it had the casting you want. I took the guts out of it to rebuild my 309.

[Stingr69]

Many "rebuilt" master cylinders these days will be newer service replacements without bleeder screws.  Still worth a look.

If you buy a correctly dated and cast number core and restore it you might save a little money but not a bunch. They need to be sleeved and have new parts installed.  Some internal parts do not come in the kit and are not available anywhere else, and you will need those so....

Compare finding and buying a correct casting number, date coded core then having it sleeved.  Add the cost for buying a non-correct "rebuilt" unit at the parts store and scavenging the internals to use in your re-sleeved core.  Maybe doing it yourself is not so cheap in the end?


My take on it - if you still have the correct core - do it yourself.  If not, it will be expensive no matter which way you go.

-Mark.

[cook_dw]

Ahhh those were the days..  Back 15-20 years ago when I was finishing high school and through college I worked at auto parts stores and when I would hit a new store or town I had a list of part numbers I would pull from their inventory and look them over..  I got lucky more than once on masters and water pumps but never could score on distributors..  Helped get extra cash when going to swap meets..   

This is one of the last of my stash that I kept for backups..  And no it isnt for sale..

[DAVEN1256]

Thanks for all the replies so far.

Advance Autoparts and maybe others (national chains), have rebuilt ones for $20-25.

Are you saying you can find master cylinders with correct casting numbers and double bleeders at the auto parts stores? I have heard of people finding parts like that at those stores but only buy chance.

I would like to get something out of the box that is ready to go rather than fixing a used core but I'll definitely consider that.

Having the correct casting number would be nice but it is not an absolute necessity......I do however, definitely want to have the correct original shape with the double bleeder valves. .........So then I ask myself, is it better to have the wrong casting number (the 5468309 for '69) or one with no casting number at all. Right Stuff, NPD, and D&R Classic all offer the correct shape with the bleeders and no casting number. I guess it's just up to me to make up my mind on that.

Going back to one of my original questions, no matter who you buy a new one from, is the quality about the same? I don't know if there are a lot of manufacturers out there or if most of the parts houses get them from the same place.

Of all the new master cylinders I have looked at online, none of them say anything about already being stainless steel sleeved. I would assume that are not. Can anyone comment on that?

Thanks.....Dave

[ko-lek-tor]

Ok. My memory was not as good as I thought. There are no bleeders. The cap alone is worth buying this part,IMO.

[bertfam]

There were lots of applications for the 5460346 master cylinder. not just the Camaro. Among them was the 68-74 Corvette, with the only difference in this case being no RPV (residual pressure valve) installed in the Corvette (4 wheel disc brakes instead of rear drums, so no RPV required).

Places like Paragon and CORVETTE CENTRAL sell the 5460346 casting master cylinder for the Corvette for around $130, so that might be an option for you. You WOULD have to add the RPV to the master cylinder though (and of course the "WT" stamp).

Paragon only sells it with the Corvette "PG" stamp, but Corvette Central sells it with or without the stamp (my above link is for the one without the stamp).

Since it's the same casting number, you would think some smart cookie would start making the 67/68 Camaro application, but NOOOOOOOO!!

Ed

[DAVEN1256]

The RPV you speak of, are you referring to the external hold off valve separate from the master cylinder or something inside of the master cylinder itself?

Dave

[bertfam]

No, the RPV is in the master cylinder. HERE'S THE CRG REPORT showing the RPV and the explanation.

Ed

[DAVEN1256]

I had no idea about the RPV internal valve. I learned something today.

So a 5460346 casting master cylinder for a Corvette is not correct for a Camaro because the RPV for the rear brakes would not be there.

What is involved in putting one of these valves into a Corvette master cylinder to make it suitable for use in a Camaro. I seems like more of a project than I would want to get into but maybe not.

Dave

[69Z28-RS]

I went to ebay looking for a RPV for a Delco MC, but only found a bunch of aftermarket RPV's.   Interestingly, they have RPV wtih 10 psi residual pressure for disk brakes, and with 2 psi residual pressure for drum brakes.  Looking at this, it seems the 'spring' shown in the CRG brake report basically 'goes with' the RPV?  ie..  if no rpv, then is the spring necessary??  Is there a source for the stock Delco RPV if you needed to add one to a MC without them?

[bertfam]

I don't know of any GM part number SPECIFICALLY stating "Residual Pressure Valve", so it may not have been able to have been ordered separately. You can see from the exploded diagram below that the RPV isn't even shown! However, there's a "Repair Unit" (Group 4.649) for the Camaro as P/N 5462708 (1967 with disc brakes) or P/N 5468449 (1968 with disc brakes), but it doesn't say what's included in the kit!

There are two "Valve assemblies" listed in the P&A. The first is under Group 4.657 and it's P/N 5462642, ("VALVE ASSY, MAIN CYLINDER CHECK"), and it's used on ALL 67-69 cars ("as required"). The second is under Group 4.658 and it's P/N 5462684, ("VALVE ASSY, POWER BRAKE CYLINDER"), and it's used on the 67-68 Camaro and the 68-69 Nova. But again, no REAL description what either these valves are for! If I were to guess, I'd say the RPV is probably P/N 5462642, but that's just a WAG.

Napa might be able to get the RPV, but to be honest, I've never researched this very much.

Ed

[69Z28-RS]

I never have either, Ed.  It was curiousity that pushed me to check ebay and then make the post...  I have a couple of extra Chevy/Corvette Delco MC's (509/DC and 309/US) that I probably should sell, but wouldn't want to misrepresent...

(Anytime I realize I'm totally ignorant on a subject, I like to try to 'fill in some of the hole'...

[JKZ27]

The check valves appear to be included in NAPA's master cyl kit  UP501 or UP472, FWIW.

[TRLAND]

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.

Dave: They are not hard to install. Pull the brass port out by threading a drywall screw into the port and pulling straight out using a claw hammer.  You can get fancy and use a finer thread screw and some washers as a puller so as not to damage the brass port but if you do the ones from the kit can replace those.  Then just put the spring, RPV, and brass fitting back in the port and carefully tap it in place with a socket. Done.

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.

[69Z28-RS]

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...

[67stripper]

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]

67stripper: There is a NOS 5460465 casting MC on eBay from D & R Classic

http://www.ebay.com/itm/GM-Master-Cylinder-NOS-Delco-Power-Drum-Brake-5474212-Camaro-67-69-Nova-68-72-/152182732317?hash=item236ecc361d:g:AkkAAOSwZVlXl~bC&vxp=mtr

[67stripper]

Thanks. Appreciate your help.

[DAVEN1256]

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]

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]

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]

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.

[69Z28-RS]

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?

[z28z11]

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

[z28z11]

Pics 3 and 4 -

[bertfam]

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]

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

[Steve68]

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]

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'...??

[DAVEN1256]

Thanks for all the replies and good discussion on this.

After considering the different ways I could've gone on this, I bought a 5468309 casting number double bleeder valve master cylinder from D&R Classic for $60. It arrived a couple of days ago and looks very nice.....There is no RPV in it but I didn't really expect one to be there. I'll pick up the rebuild kit from NAPA to get one.

I had considered a double bleeder valve MC with no casting number on it but in the pictures of everyone I looked at, if the pictures were correct, the gold irradiate tops had no writing stamped in them.

I thought I had stumbled on a good deal at Autozone with the following MC for $21 .....

http://www.autozone.com/brakes-and-traction-control/master-cylinder-brake-system/remanufactured-master-cylinder-brake-system-/718064/

The picture shows the ports for the double bleeders but when I checked out this MC in person at three different Autozones, none of them had the bleeder ports.

I could have messed around with this forever but needed to get it done. I think I'll be happy with what I ended up getting.

I'm really glad the subject of the RPV came up on this because if hadn't been mentioned, I would have never known and installed the new MC without one.

Dave

[DAVEN1256]

Now I have new wrinkle !!!

I went to NAPA and spent the $35 for the master cylinder rebuild kit (p/n UP501) just to get one RPV valve out it.

I went out this morning to install it. I pulled the brass seat out of the rear port on my new master cylinder. It came out without a problem. A soon as I saw the diameter of the of the pressed in portion of that seat and the diameter of the port behind it, I knew I was in trouble!

The diameter of the "pressed in" portion of the brass seat I took out of the new master cylinder is 1/4" diameter. The diameter of the same area of the new brass seat in the rebuild kit is 3/8" diameter.

The machined out port behind the brass seat is not wide enough or long enough to install the RPV. The port is 1/4" in diameter. The RPV valve is just over 5/16" diameter. The depth of the port is about 3/8" in length. The RPV valve itself is 1/2" long and then add to that the length of the spring.....

The bottom line is THIS RPV IS NOT GOING TO WORK IN THIS MASTER CYLINDER !!!

By the way, the rear port of the parts store master cylinder that has been in this car for the past 15 years or so is identical to the one I just bought. The RPV and replacement brass seat would not have worked in that one either.

I don't know if the problem is the master cylinder or the rebuild kit but I would quicker thing it's the master cylinder.

Now I have to figure out what to do next. I've already painted the new master cylinder black so I doubt that's returnable. I could probably return the rebuild kit but not sure what my next move would be after that.

In the picture, you see the RPV valve and the replacement seat from the rebuild kit together next to seat that came out of the new master cylinder.

[TRLAND]

Dave,

Hard to tell from the pics but are you saying the new brass port that came with the kit will not fit down into the MC because the hole is not machined deep enough? I could be forgetting, but it seems to me the pressed in part on the ones I've worked on are the straight sides at the base of the cone, not the bottom portion of the brass seat. Does the spring fit down into the smaller lip? The rubber flap portion of the RPV should fit into the brass seat.

On my drum/drum MC the spring rests at the back of the port (behind where your smallest hole is). Maybe that MC was designed for front and rear discs so it didn't have provisions for drum brake RPVs.

[DAVEN1256]

I drew up a little sketch that I hope will clarify what I am trying to explain. It is a cross section of the port and is fairly close to scale.

On the left shows how the brass seat supplied with the master cylinder sits inside the port. The part of the port that the brass seat press fits into is 1/4" diameter.

On the right shows the port dimensions relative to the dimensions of the RPV valve and the new replacement seat. Both the RPV and the replacement brass seat are too large in diameter to fit in the part of the port that they are supposed to.  The combined length of the RPV and new brass seat is also too long to fit in that part of the port. The port is too small in length and diameter.

I got this master cylinder from D&R Classics and it is called out for a '67-'69 Camaro with disc brakes but the rear port should still be for drum brakes.

Dave

http://www.drclassic.com/catalog/Camaro/Brake/Y00076-OE.html

[TRLAND]

I hate to say it but based on your excellent drawings I'm feeling your pain.  You aren't alone: see Steve68's comments and link in #28 above.  I've been through a similar search to get a correct looking MC with RPVs.  It seems any reproductions have issues when it comes to RPVs.  I considered machining the ports correctly or adding inline aftermarket RPVs but I got lucky with vendors accepting returns and finding a good original rebuilt unit on eBay and I added the RPVs.

[DAVEN1256]

Geez, you wouldn't think getting your brake system going with the correct parts would be this tough.

I read all of the thread that Steve posted the link to in post #28. There's a lot of good info in there.

With everything I've read recently about the RPV's,  it seems that there is no question that they are necessary for good braking. That being said I am at a loss to understand how companies can be manufacturing master cylinders without them.....especially when we are dealing with something so critical to your safety as the braking system.

I guess the only way to get a correct looking double bleeder MC with the proper RPV is to find an original to rebuild that has the port machined correctly to receive the RPV.......I certainly can't keep buying repos from different companies and pulling the brass seats out of them to see if I can get the RPV in there.

I'd appreciate if anyone else has any other suggestions on which way to go next on this.

Thanks.....Dave
 

[janobyte]

I am at a loss on this. I also ordered a correct MC for the Z as the OE was obviously replaced with a non-bleeder type Has been on since at least 76'. After reading the threads I checked the new one, no resistance, no RPV. Thought maybe my feel was off, so pulled the brass on the old one to see if possibly one was present...no. That being said, always had good pedal, no braking issues??

Car is power disc/drum, single line to the rear(no valve on the sub-frame)

[DAVEN1256]

I wonder if the people who feel they have good braking without the RPV have become accustomed to what they have and that feels normal. And if an PRV was installed, would the braking be better? Maybe like when you think you are seeing just fine through eye glasses you've had for a long time but the glasses are gradually scratching and your prescription is gradually changing. Then you look through a new pair of glasses for the first time and your astounded by how clearly you can see........I don't know.....just a thought.

I am going to start a new thread on this as this RPV discussion got tacked on to what started out as question where to buy a master cylinder and may not be getting seen much.

Dave

[janobyte]

A poor braking car is a poor braking car. However, never stopped in snow, rain, or even fast in gravel, so can't say how it would perform in those conditions.

From what I've read on different sites, some stated they had no issues, however, I certainly intend on adding the RPV to the rear port, which puts me in the same boat as you. States in the chassis service manual, rebuilding the MC, replace the rear, not front if equipped with disc, as premature wear will occur.

I'm going to order the rebuild kit tomorrow, yup for 1 valve. MC was from HBC with correct script, we'll see this weekend if brass are the same. Not the only GM's with disc/drum set ups in the late 60's, has to be a solution. New thread on this is a good idea.

Not going through all this to have a car with stopping issues which weren't present prior to re-build

[janobyte]

DAVEN, just ordered this:ACDelco 18G1183 Professional Brake Master Cylinder Repair Kit with Boot, Seals, Washers, Caps, and Piston, lists for 68 Z/28 power assist disc/drum.

If it works, will send you my MC number.

[DAVEN1256]

Let me try a better example of what I was trying to say when I used the eyeglasses comparison.

I used to have an older daily driver but would rent a car when going on a trip. The daily driver had no braking problems but after getting back into it after a week in newer, better car, the brakes felt like crap. Having experienced something better made realize they were mediocre at best ......So my question should have been, "Would what feels like a good braking car that didn't have an RPV maybe become a better braking car if it had one?" I wonder.

I looked at the rebuild kit you ordered and it uses the exact same photo as the kit I got from NAPA. They might be the same kit but can't be sure. I'm guessing the RPV valves in your kit would be the same size as the ones in the NAPA kit but can't be sure of that either.

If they are the same size, then you have to hope the port in your new master cylinder is machined differently than the one in mine and will accept the RPV valve.

I would love to know how you make out.

Dave

[DAVEN1256]

I started a new thread on this subject of RPVs not fitting into repro master cylinders.......

http://www.camaros.org/forum/index.php?topic=15181.new;topicseen#new