gimpyrobb : Master cylinder

Master cylinder
Post by gimpyrobb on Jul 10, 2006, 9:01am

While at the F.E. I had no pedal a couple of times when I hit the brakes. Now that I have had some time to catch up on things at work and home, I looked into my brake system. I filled up the master cyl. and have developed a leak. I can't pin point exactly where its at, but have decided its time to steo up to the corvette master. What was the year again? I will probably do the upgrade when I put in the big block. How hard is it to put in a hydro-boost system? I have access to the parts so I'm thinking about going that way. Also I will be putting in power steering. Thanks in advance.

Re: Master cylinder
Post by brute4c on Jul 10, 2006, 9:13am

From Barrman:

Many people want to get rid of the stock single line master cylinder. Either for better braking or to replace a worn out stock one. Many have done this already. This post is not about arguing what might fit or power or non power. This is a swap that I have done to my truck using the following parts. The part numbers are NAPA and the prices are what I paid for them last week.

1976 Corvette non power disc/disc master cylinder: #10-1371 $23.99

30" 3/16" brake line: #813-1205 $2.49

3/16" line plug: #131 x 3 $.29

3/16" line butt connector splice: #302 X 2 $1.99

1/4" reducer from mc to 1/4 line: #7913

3/16" reducer from mc to 3/16 line: #7914


The swap involved pulling the stock master cylinder off. Bolting the Corvette one on using the stock mount and pedal push rod. (I think adding 1/2 to 1 inch to the stock rod would make the pedal have instant pressure from its rest height. Instead of the 2-3 inch travel I get now. I will add power brakes later and see no need to mess with it twice.) I used the reducer and connected the stock brake line to the port closest to the firewall on the new master cylinder.

I then disconnected the line going to the rear brakes from the distribution block that includes the brake light pressure switch. I put the plug in the block. Put the splice on the line and connect the new 30" line to it. Slightly bend it so it goes toward the master cylinder. I now had a new line sticking about 10 inches above the master cylinder. I put a loop in it the diameter of my fist and it came out right at the master cylinder. I connected it and the reducer to the master cylinder. That is it.

I did pull the lines off of the master to "bench bleed" it on the truck using the pedal. I just hooked the lines back up and had firm brakes right away. I vacuum bled the right rear wheel cylinder to get the air the 30" line contained out of the system. I can now here the brake shoe springs working when I hit the brakes with the engine off. Not so before.

The 1976 Corvette had the option of a non power brake system with disc front and rear. That means the master cylinder had to push a lot of fluid to stop the car. They have the biggest pistons of the same size front and rear without any proportioning valve that can be found nationwide. That makes them a perfect swap into our drum front and rear trucks. Spicergear figured this out years ago and the rest of us are just using his research for our benifit. Thanks Tom.


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From spicergear:

Thanks Tim. When I did my conversion I wanted the largest piston I could find that was on a cheap part and plenty of fluid. The '76 'Vette non power had that. At like $22, it a nice part. Let me add, I ran one for years and had great brakes 'til I tore up the pads in mud. Now...all that being said, we cannot discredit or ignore mechanical theory or proven facts that our own Luckypabst/Chris has brought up time and time again.

LuckyPabst wrote:

Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">Everyone that has used that MC (that I'm aware of) have not used a residual pressure valve without any complaints.

That said, brake theory states that drum brakes require about 10 psi held in the lines to keep the brake shoes out where they need to be. Disc brakes need closer to 2 psi.

I've heard different stories about which master cylinders have built in valves and which don't so I won't go there. If you do decide you want to run them, the big aftermarket brake companies all have a version of their own and most every hi-po supplier can get them.

Chris</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>


Wilwood, Baer, (etc) have them. Usually in the $15-$20 dollar range. I'm going to put a set in the system I'm building for Katie's truck based on my original Corvette master cylinder...it can't hurt.

Thanks Chris


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From Luckypabst:

The Vette cylinder is nice and all but for me the Jeep dual cylinder was the way to go.
It bolted in place of the original, requiring ONLY the addition of the second line down to the distribution block.
It was designed to work in a large GVW truck with 4 wheel drum brakes (and endorsed by the Jeep corporation)
It was cheap at around 30 bucks new.

From the online parts list:

Wagner #F66857
Raybestos #36246
CarQuest #20-1331
A1 Cardone #A-1-10-1331
from MudAnchor #1759 5/3/99

I'd like to add the Bendix number that I used - BXH 11331
And I believe the application was early/mid 70's J-series with 8600 lb GVW and maybe dual wheels or something to that effect.

Chris


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From compexp:

If you use this cylinder, as I did, you will need the adapters listed in Barrman's post at the top, as well as a Napa 7913 Dual Master Cylinder Adapter - which is required to go from the 20-1331 cylinder to a standard 1/4" line. This cylinder uses a weird thread (9/16" x 18 ), and it took me 6 stops in town today to find the right adapter. the Napa 7913 works great!

rich

Re: Master cylinder
Post by maccj715 on Jul 11, 2006, 11:37pm

i did this on a cj5 and am now doing it to my m715 i used 84 chevy suburban power brakes the two middle holes line up with the original without drilling i then marked and drilled the other four holes measured the original rod to firewall distance cut the suburban rod then drilled and tapped for 3/8 16 thread then cut the m715 rod and threaded it 3/8 16 its just the right size, i used the sub lines and proportion valve the front brake lines hook right up to it but the rear line is a different size and has to be adapted. the distribution block mount hole works for a place to mount the suburban prop valvei just added a piece of angle iron for the second bolt hole on it and massaged the front lines to fit ps: the cj5 will rip the skin off your teeth if you stomp on the pedal