In a previous thread I inquired about how to convert a G body to manual brakes. See here: http://www.hotrodders.com/t66458.html

Well, mission accomplished, my car officially has brakes again. I thought I'd share how I did it.

Here's the basics:

I bought an S10 manual master cylinder from a wrecker. With the master cylinder I also took the factory block off plate, pushrod, and pushrod retainer cup. The pushrod fits really nicely into the back of the master cylinder. The metal cup holds the pushrod against the back of the piston so that it is impossible for the pushrod to fall out of place. This is very important for a power to manual conversion because with power brakes the pushrod is locked into the booster. If you switch to manual it's necessary to make sure the pushrod cannot fall out.
The S10 pushrod is about two times longer than it needs to be for a G body. Pictured is the rod end I used to shorten the pushrod.


I measured the length required and cut the pushrod. I threaded it and attached a 3/8 rod end. The rod end is a high quality piece. With the fine threads this pushrod is very sturdy and I won't have to worry about it at all.


These are all the pieces layed out. With the booster removed there is a large hole in the firewall. The stock S10 blocking plate fills it nicely. It is also required to hold the retaining cup against the master cylinder. I'm using the stock G body pedals. The pedals came with two holes drilled. The lower hole is used for power brakes. The top hole is used for manual brakes. I welded a bolt through the upper hole for the new pushrod attachment. I also welded four bolts to the pedal bracket to make the studs which will go through the firewall.


This is the pedal, pushrod, and master cylinder assembled pretty much as it will be in the car.


This is another view with the pushrod more visible. A nice thing about the threaded end is that it's possible to make adjustments in pushrod length. For final assembly I used some loctite and locked the rod end with the nut. Even if the rod end loosens (which it won't), it's impossible for it to fall apart. The longer the rod is, the higher the brake pedal. It can only move so far, so it's impossible for the rod to come apart. As with the factory setup, the rod end is spaced with washers and a held in place with a cotter pin.


This is the master cylinder installed on the firewall. It's nice having that big ugly booster out of there. Of course, now I have to clean up all the wires that were hiding behind the booster. The S10 resevoir doesn't fit too well. I cut a little notch out of the hood bracing so that I have about an inch clearance. On my next trip to the wrecker I'm going to look for a smaller resevoir with more of an angle. This one does work fine however.


Total cost: master cylinder $15, rod end $15.50 = total $31.50 Canadian.

As a concurrent upgrade, I also put 7/8" wheel cylinders from a manual braked S10 in my rear drums. These should help increase the power of the rear drums. The factory G body wheel cylinders are 3/4".

Results:
I am very happy with this conversion. My engine doesn't make enough vacuum to run power brakes well enough. Now I have consistent braking with a simple system. I've only tested the new brakes for one day, but so far they seem to work quite well. The pedal isn't too heavy. You have to push a bit harder, but it's no big deal. The pedal travels a bit further than power brakes; but I don't mind that either. The braking power seems fine; its comparable to normally working power brakes. In the future I plan on swaping the front discs to 12" from a caprice station wagon. That's it.
dh

that is pretty clever.

good job!

JB

Good work.

Post back on what you get the reservoir from and how it fits.

Edit:
How are your brake lines routed? My 87 s10 has the front of the MC going to the rear brakes and the rear fitting of the MC going to the front brakes....just currious if it mattered

there was an article recently in the latest Street Rodder, i think, that explains master cylinders pretty well.

basically, in the old days, one reservoir did the front and back. then with discs on the front and drums on the back there was a large reservoir for the discs and a smaller reservoir for the drums.

and if there is 2 large reservoirs of equal size then that would be for a disc/disc combo.

just something to keep in mind if you're ever shopping at the wrecker's for an MC and want to get the right one.

JB

I haven't had a chance to go to the wrecker and search for another resevoir yet. This one is working fine for the moment. When I do get another one I'll post a picture.

As for the brake lines, I just kept them as they were. There isn't much difference between the g body and s10 master cylinders. Actually, I just assumed that the lines would stay in the analagous fittings (front and back).
dh

I'm doing something different, but need to know where you got that rod end? I bought a 7" dual diaphragm booster because the stock 9" didnt clear the tall valve covers I needed on my big block to clear the stud girdles. The booster just has a 9/16 or so threaded rod in the bakc and no end, and the place i bought it from basically said good luck "making" something to work because they only sell them for 57 chevys. For the life of me I cannot find anything to screw onto the rod to make it work on my pedal. Help would be greatly GREATLY appreciated!

Good job that set up looks nice and clean. I'll have to remember that one.

The rod end took a bit of searching. At first I tried the home depot type stores. That was a waste of time. They didn't have anything even close. And even if they had it probably would've been some cheap metal I wouldn't trust on my brakes.
After getting some advice from a local machine shop, I found the rod end at a local industrial supply type store. He had a wide assortment of rod ends. I showed him the size of the pushrod, and he came back with the appropriate rod end. I threaded the pushrod myself to match the rod end.

If you don't know of any industrial supply shops in your area, try talking to a machine shop. Perhaps they can point you in the right direction. Good luck,
dh