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o.k. I did a search, just need help on how to fix. I put a power boost and a power disc. 1 1/8" M C . on a 68 manual drum brakes all the way around,do not have a proportioning valve on car. They work great ,well to great,,, they will put you through the windshield. What do I need to do to fix ? Did I use the wrong M C ? can I install a proportioning valve or an adjustable valve ? Sorry for asking something that has been on before, but would appreciate any help.. Thanks
 

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Ted, been there; done that. there should be a lower hole in your brake pedal arm. Upper is for manual, lower for power. If there is no hole, then you have to drill the arm. lets us know if you have the hole. The parts you have is all correct, just the angle of the booster rod is not correct.

And welcome to TC!
 

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Kevin, sorry I didn't say, but I did move the rod to the bottom hole on the pedal ,,,now this had manual brakes and I put new brake lines on ,when I did this . And I did sh can the disc brake hold off valve that is on the drivers side frame rail. I used a straight coupling, at the time I didn't know what it was,just thought it was a brass fitting......This thing will stop on a dime and give you a nickle in change. I can drive it but I know how it is. But you have to watch what you are doing. I did something wrong. I got the boost from Ricks and the power MC from NPT. Thanks
 

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Hmm, interesting. Did you have the brakes working fine before you added the booster? If you have the shoes on wrong or too tight, strange things can happen. Also, the MC rods that come in the repro kits are 1/8 inch too long, but that normally shows up as poor braking, not exaggerated braking.

The hold off valve under the car was for certain optioned cars, you dont really need one. I have the repro mc from belair bobs and a repro booster from right stuff (I think repro is all the same manufacturer) and no valves and it works fine.
 

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There are all sorts of mixed names, but to the best of my knowledge -- that valve on the driver-side frame rail is the stock proportioning valve; the disc brake "hold-off" valve was installed up front by the master cylinder.

In any case, the proportioning valve is there to keep the rear wheels from locking up before the fronts by reducing the pressure to the rear at moderate/heavy braking. You may want to make sure you don't have any issues without it.

When I converted my '69 from manual to power drums, I had the same problem -- it would lock up the wheels VERY easily and was quite hard to modulate to prevent lockup. I was still running the "stock" 1" master though, so the 1+1/8" should be a little better. I just got used to being gentle on the whoa pedal before I swapped over to power discs.

To tone things down, I think your options would be an even larger diameter master cylinder (more force required with lower pedal travel), smaller diameter wheel cylinders (same effect), or a smaller/reduced-boost power booster...
 
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