Once again...Which is the correct Master for a 1st generation disc conversion? ..and part number?

[66BeachCruiser]

Alright, I've been searching and searching and there never is clear answers and plus all NAPA numbers have since changed. I'm getting ready to do the disc brake conversion and am stumpped on what master cylinder to get. I was originally going to get a second gen and add risidual valves but after reading it sounds like there might be 10 valve residuals in each because they were intended for drums? So after reading repeated readings of recommendations I landed on the 69 vette master recommendation. And I'll just add residuals to that. After reading, it seems a master with a 1.125" size bore will have a better pedal height opposed to a 1" bore master. Since I'm going manual and not power I remember reading to choose manual. I looked at the autoparts stores online and can't find that master. What I did find is the 69 corvette master manual with 1" bore. The 69 corvette master that I found with a 1.125" bore is power. So, do I choose the last master cylinder that I mentioned with power? Will that one work or not because its power? What is the correct master to use for this disk conversion? ...which I can add correct residual valves to later.

This is the link to the 69 corvette master with the 1.125" bore ...it is for power. Is this the one to get?

http://www.autozone.com/autozone/parts/Fenco-Reman-Master-Cylinder-Brake-System/1969-Chevrolet-Corvette/_/N-iqw2eZ8kn47?itemIdentifier=718064_0_0_2867%2C3912

[Optik]

As a general rule, the smaller the bore on the master cylinder, the less pressure is required to apply the brakes, but more pedal travel is required. The larger bore master will take less pedal but more effort to apply the brakes. In your case I would try the corvette disk/drum NON-power master with the smaller bore first, and if that doesn't work then try a different one with the next larger bore size. I would not try the power brake corvette master as pushrod length could be an issue among other things.
Let us know how it turns out....

[G-Man]

http://www.vintage-vans.com/discbrakeinstallation.html

[66BeachCruiser]

Thanks Tim,

So I went ahead and got that 69 Corvette master for disk set up with the 1" bore...manual. You're right, if I'm not happy with the pedal I'll just try the next bore size up. I ordered it online from Autozone and should be getting a home shipment.



G-Man, Thanks for that link. Yea, that write up pretty much came along with my bracket purchase. I have the actual printout with me. I've been reading that along with all the other master cylinder posts. Everyone has different opinions on a master and never just one part number. Well, the link, opposed to the actual printout is pretty good because I can actually click on the different links M1 has posted for suggested parts like residual valves.

Once I get my master cylinder, install it, and feel happy about it, I'll post up a confirmed part number here.
If anyone has a confirmed part number from any auto store please post it.

[G-Man]

I like the corvette master because it's lower profile and I thought because it was for a vette if would be $$$ , but it was reseasonable

[m1dadio]

Ok I have read all your posts.

That old link that g man posted is the outdated version and the one you get when you by your brackets has some different information and the links are available to you if you open it from the email I sent you when you purchased your brackets.

First thing to be said is that the parts stores have no idea why "THEY" call a master "a power master" or a "manual master". The bore size has absolutely noting to do with whether any master is used as manual or power. They only now that their book says "that car had this master used when it came with the power option". But Gm could have picked many other masters to use with the power option and they didn't, they picked the one the parts book says. So everybody turns that into meaning that the difference between a master used as manual or power has to do with bore size and that's what makes you confused.

What Optic said is correct.

Optik

As a general rule, the smaller the bore on the master cylinder, the less pressure is required to apply the brakes, but more pedal travel is required. The larger bore master will take less pedal but more effort to apply the brakes. In your case I would try the corvette disk/drum NON-power master with the smaller bore first, and if that doesn't work then try a different one with the next larger bore size. I would not try the power brake corvette master as pushrod length could be an issue among other things.
Let us know how it turns out....

If you are going to have manual brakes, your master needs to have the "DEEP hole" were the push rod inserts. That hole is deep to keep the push rod from falling out should you let the pedal fly up fast.

A master used with a booster will have a shallow hole because of the way the push rod is built into the booster and bolted to the master it cannot fall out.

Manual brake = deep hole

power brake = shallow hole

Absolutely nothing else about the master has anything to do with power or manual.

Both the deep hole and the shallow hole come in any different bore sizes.

Like Optic says; Different bore sizes is a trade off ; smaller bore is easier to push = longer pedal travel and larger bore may be harder to push but has less pedal travel.

The depth of the push rod hole and the bore sizes come in any combination you want. But the average parts store counter person will be clueless if you try to tell him this.

Misconception #2: Everybody in the aftermarket brake business uses the late 60's "STYLE" of corvette master, not because it has anything to do with disc or drum or power or manual, but only because its lower profile with larger fluid resivours and the fact that it comes with many different combinations of line connection outlets and comes with any combination of bore and or push rod hole depth and that is comes with no internal residual valves makes it a very "Universal" master cylinder choice for custom brake set ups.

The only problem is you have to pick what you need and know why you are picking that. Which is why I tell everybody, if you want to build a custom brake system you need to study up on what you are doing because there is no "out of the box one size fits all"

So, 66beachcruiser you have done the right thing, first reading up what you could find to read then bringing forward your questions.
You are going to be happy with the outcome. Your master must have a deep push rod hole for manual and the bore size is an option. many people like the 1" bore, many people like the 1.125" bore.

Here is a link where you can see the same master cylinder style of casting (the corvette style) available in any combination of lines, bores and push rod hole depth you want.

indecently, some aftermarket master suppliers all come as a deep hole for manual but all come with a bullet shaped plug you pop in the hole to convert it to a shallow hole for power booster installation.

look over the descriptions of these masters

duel ports means the brake lines can come out either side left or right cuz it has four line outlets.

http://www.tuffstuffperformance.com/index.cfm/page/ptype=results/Category_ID=210/home_id=-2/mode=cat/cat210.htm

hope this helps

M1D

[66BeachCruiser]

master too big?

With the advise given I went ahead an orderd the 69 corvette disk/drum master with 1" bore. To me it still seems a bit wide after cutting off the master cylinder mounting bracket. I went ahead and cut off more of the bracket so it could fit but it is still binding and still doesn't fit so I could bolt it on. And trying to put it in there not only does it bind with the bracket but also with the gas pedal rods. I thought it was supposed to be low profile but the top of the master is in the way with the rods. I'm about to take it back to Autozone and see what they can bring out from the back. If someone can post up a part number of one that worked for them with plenty of clearance that would be great. This is the Autozone linke to the one I bought
http://www.autozone.com/autozone/par...er=718049_0_0_ Did I get the wrong one, or is this what others got?

[66BeachCruiser]

Well, I took the master out of the box before returning it and compared it to the original one side to side. It does seem to be lower in profile than the original one. So the low profile shouldn't be a problem. What makes it wider hitting the master cylinder mounting bracket is the lid retainers that stick out some. Maybe I should try bending them in some. Don't know if I should mess with it or get something different. Anyone else have this issue or use another master?

[kookykrispy]

Jose,

I am running that corvette style master cylinder in my '65. I had the same problem with the width being an issue. I used a sawzall and trimmed material away from both sides of the original mounting bracket in order to fit the vette master in there and allow the lid retainer bails room.

Here's some pics showing my install, and detailing where I cut:







I am running the disc/drum non-power master cylinder with a 70-72 chevelle style GM proportioning/combination valve. This works well for my front disc/rear drum non-power brakes. If I recall correctly, mine has a 1" bore.

As far as the throttle linkage hitting the master cylinder, I went to a cable operated throttle (red cable in the pics)... but another option is if you can source a 2nd gen throttle rod, they are shaped differently and designed to work with the larger dual master cylinder. The 2nd gen rod has a bend that goes around the master cylinder, and then back towards the engine.

[m1dadio]

That is a correct master that can be used.

I first used the M1372 which is the "New" version but the same as the M1371 Re-man master.

The pencil lines marked where I cut out the mounting bracket.




There was plenty of throttle rod clearance, at least 1/2" clearance and that is all stock L6 set up


And i had to block down the sway bar 2"


Like I said before there is hardly two vans alike when it comes to modifying then, you have to be able to deal with whatever gets in your way. Maybe you need to bend your throttle rod a bit.

M1D

[66BeachCruiser]

What I originally cut off of the bracket was based on other people's descriptions and pictures of their cut outs. Well as I have experienced and I see that others here have, you really have to cut out more. This is the original cut out. And with this 69 corvette master, that wont do.



I had to cut out a little wider to make room for those master cylinder lid retainers. They stick out enough to create clearance problems. Even this wasn't enough.



My sawzall blades kept getting bent up on the rods when I tried cutting deeper. I don't want to take the rods off to get them out of the way. So even when the next layer wasn't enough I just went ahead and chipped away so that the retainers to the master would have clearance. I'll try grinding it clean later. But it fits and rods don't seem to be an issue now. Its mounted flush. I haven't bench bled the master yet, just mocking everything up.

[66BeachCruiser]

Jose,

I am running the disc/drum non-power master cylinder with a 70-72 chevelle style GM proportioning/combination valve. This works well for my front disc/rear drum non-power brakes. If I recall correctly, mine has a 1" bore.

This is my mock up. I'm just waiting to get the residual valves to make the final bends. Good tip on the Chevelle proportioning valve. Is the proportioining/combination valve the only thing you used or did you have to add other valves? Do they include the necessary valves inside it for rear drums and front disks? If this is all I need instead of the seperate 10lb residual for the back and 2lb residual valve for the front I'll just look for that proportioning valve. Do the local shops carry this like auto zone or Napa or special order? Thanks.

[kookykrispy]

I didn't want to mess with adjustments and residual valves, etc.

This is the same proportioning/combination valve that comes with the camaro/chevelle disc brake kits. I think this design was factory for 70-71-72 chevelle. I've used this same prop/combo valve on three GM front disc brake conversions so far, and it always worked great. You do not need any additional residual valves, just run your lines and bleed the system.

I actually bought my master cylinder in a kit that came with the master cylinder, the proportioning valve, the 2 short lines that go between them, and a bracket (which I modified for use on my van)

Here's a listing for the prop/combo valve itself:

http://www.ebay.com/itm/GM-PROPORTIONING-PROP-VALVE-DISC-DRUM-/380607373161?pt=Vintage_Car_Truck_Parts_Accessories&hash=item589df79f69&vxp=mtr

[Vanner68]

Cool! Simplifies things greatly, and looks more like a stock brake system!

One of these days I'm going to do the G20 version, but I hope no one is holding their breath, it will happen as time and money allow....