Manual brakes

[87geeinn]

I hope this will be informative for others as it will be a learning experience for me as well. I am in the process of converting my powermaster brake system to a completely manual system utilizing the manual brakes master cylinder from an early 80's Chevy S-10 unit (part #10-1905). From my reading, I have gathered that the biggest obstacle with this conversion is the issue of obtaining/fabricating the correct length pushrod and the issue of its retention in the back of the master cylinder. Here's what I've done so far:

Went to the salvage yard and destroyed, er...removed the pushrod from the vacuum booster assembly off of an ol' G-Body Cutlass. I had to use a Dremel to cut all the pieces off of it as seen in the photo in this thread. This pushrod was almost the perfect length to allow for the pedal to remain in the same position as before, while also utilizing the same powermaster pushrod mounting location for the proper ratio. However, I needed to put the Dremel to work again and hog out the ring end so that it was big enough to slide over the post on the pedal.

In this configuration, the only thing creating a positive stop of the pedal and holding the pushrod in the back of the master cylinder is the cruise control and brake switches (once they are reinstalled). I was not comfortable with this since any reasonable upward force on the pedal could force the brake and cruise switches out and cause the pushrod to disengage from the master cylinder . To overcome this, I very carefully drilled and tapped a hole on the pedal bracket right between the cruise control and brake switch holes. I threaded a grade 5 hex head bolt through the hole and positioned it so that when the piston in the master cylinder was fully released, it was just touching the head of the bolt. Then I secured it with a nut and some red loctite. This creates a very positive stop and there really is no way for the pushrod to become disengaged unless the piston in the master cylinder binds (never heard of this happening though).

With a full mockup of how it will be installed in the car, the pushrod travels a very linear path when actuating the pedal. Thoughts?

 

[Scott Atk]

Nice Job and great idea!!

 

[87geeinn]

Scott, no....thank you! Most of the ideas that I have incorporated into this brake job were gathered from reading prior posts that you have chimed in on. I have two questions:

#1) Which way do the lines connect to this particular master cylinder? Does the bigger line (front brakes) connect to the front-most port and the skinnier line (rear brakes) connect to the rear-most port? From my readings, I seem to remember that the Powermaster had them backwards or something. Kinda confused here.

#2) Will the stock proportioning valve be okay with this setup (completely stock front discs and rear drums) or do I need an aftermarket valve to adjust for bias? In other words, does this master cylinder change the bias significantly enough to warrant an aftermarket proportioning valve?

Thanks,

-Austin

 

[Scott Atk]

You should be fine with your prop valve, I have a factory disc/disc valve in mine (rear Wilwood disks). I don't remember for sure but I certainly don't remember criss-crossing the lines when I hooked it up, so I would say, hook it up the same. Good luck, once you get used to the pedal feel, you will like it!

 

[87geeinn]

That's great news because I don't feel like fiddle-farting around with the brake lines. I might buy some stainless flex lines to replace the rubber lines depending on how they look (haven't looked under there in a while), bench bleed the master cyliner, bleed all fours, and be done with it. I feel like a burden was lifted when I took the Powermonster out...literally and figuratively. I never did trust that thing and damn did it take up a lot of space.

 

[charlief1]

If you would do a little more in depth write up and post it in the "how to" section it would be a good thing. Thanks for the info.

 

[87geeinn]

If you would do a little more in depth write up and post it in the "how to" section it would be a good thing. Thanks for the info.

I may just do that in a couple of days once I get more time. BTW, I did just do the hoodliner article in the "How To" section.

 

[Scott Atk]

That's great news because I don't feel like fiddle-farting around with the brake lines. I might buy some stainless flex lines to replace the rubber lines depending on how they look (haven't looked under there in a while), bench bleed the master cyliner, bleed all fours, and be done with it. I feel like a burden was lifted when I took the Powermonster out...literally and figuratively. I never did trust that thing and damn did it take up a lot of space.

If you're talking about the rubber line under the hood, that will come out with the PM. The steel lines with the corkscrew looking section will screw right into the master. Now, if you're talking about the rubber lines that go to the calipers, then never mind. Those would be nice to change

 

[87geeinn]

Yep, was referring to the three flexible lines; one to each caliper and the one near the rear end housing. Hell, might even do rear cylinders too. That way, I will have a completely fresh system.