Where to by correct master cylinder?

[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