I swapped my '63 wagon over to front discs. I am using Caddy calipers on drilled/slotted 95 truck rotors with ceramic pads. The wagon is turbo'd so I can't run the power booster. I switched out the single bowl M/C and booster for a dual bowl M/C from a '60s Nova with manual front discs. The M/C is brand new, the lines are all new, I and using the original distribution block with a plug on the rear brake port. The rear brakes are now tied to the rear bowl on the MC. I made an adjustable pushrod for the pedal and the MC end of the pushrod is rounded so it won't bind up. Here is the problem- the brakes are rock hard. I have about 3/4" travel and then its like pushing concrete. This is a manual disc brake MC, it shouldn't have that hard of a pedal. I have to use both feet to get the thing to stop. I have tried two masters on the car, I originally made the mistake of using a power MC, but it feels the same. I can't use the original single bowl with disc brakes, the caliper will drain that little resevoir. Any ideas? I don't have much room, the MC is less than 2" from the downpipe on the driver side. the original booster and MC fit, BUT it won't with a dual res. Any ideas? I am runing out of ideas. I have a race-style MC that has a larger bowl, it would probably work with the booster and the downpipes, but it is a single bowl. Other than relocating the booster and making the MC sit over the down pipe, I am out of ideas. The stock brakes were not sufficient in stopping the car before I put the turbos on it, now its just scary.
If you are using the same location on the pedal for your push rod as the power brakes used your leverage is wrong. With a swing pedal you need to move up closer to the pivot point.
Even on heavier cars, properly configured manual disc brakes are a viable option. On lighter cars with discs, manual brakes are even more user friendly. So, what you are trying to do can be done. It sounds like the piston area of your master cylinder to caliper/wheel cylinder area is too far off. A smaller bore master cylinder will help, but realize you will be trading less pedal effort for more pedal travel. Are you not using a power servo because the turbo effects available vacuum? If that's it, and you want to use a servo, various types of vacuum pumps are available. A vacuum reservoir and check valve is another option. reservoir If the issue is space for the servo, remote servos can be had.
The vacuum is not the problem, the Buick has a factory vacuum can and the car makes 20 pounds of vacuum when you are not in the boost. The problem is fitment. Look at the pic- there is not enough room for the booster AND a dual res. I may have to try the race-style MC, it has a bigger resevoir but its a single, so its shorter. I will have to adapt it to the booster though. I am using a 1 1/8" bore manual disc MC, its the smallest I can get off the shelf locally. Moving the contact point on the pedal would a be a tough call. I think that might put too much angle on the pushrod, there is only about 3" of pushrod, its is actually quite tight for a 26' long car!
There were some dodge vans in the 1970 that had a power brake unit mounted sideways on the firewall with a bell crank from the pedal to work it.
this is just my 2cents but it seems to me the way you plumbed your system, you have nothing to balance the system when you step on the pedal, your back brakes are applied and not the front. Jack up the car, have someone step on the pedal. I think you will be able to turn the front wheels by hand and not the back. The fix is a GM style proportioning valve, speedway part #910-31351 or #910-31366. I do not recommend an adjustable proportioning valve in the rear. The GM type valve works much better. Good luck. Terry
I have tried that actually, the front brakes are locked up tight when you press the brakes. If it were a prop valve issue, the rear brakes would lock up when you hit the brakes, but they don't. In fact, the front brakes lock before the rears, as they should, you just have to stand on the damn pedal. Keep the ideas coming, we are bound to find an answer eventually. I have been dealing with this for weeks, I have tried everything I can think of save for putting a little air in the line, creating a cushion. Horrible idea, that's why I haven't tried it.
Way too big a bore for manual, even with big calipers. You want 15/16" to 1" bore max to do this. Also, the small chamber in front is plumbed to the rear line correct?
Stock bore manual or power is 1" upon research. I would need a pic of the backside of the master to help out here...
Both chambers are the same size on the master. The book at the parts store showed this MC to be a front disc rear drum manual brake MC. I tried to get one that was 1" bore, but they didn't have any in stock and they had this one, which states it is in fact a manual disc MC for a Nova/ChevyII/Corvair. I have made so many damn brake lines for this car it is ridiculous. I think in the current configuration, the front bowl is on the front brakes. The bowls are the same size, there is nothing to differentiate them. I have seen that particular MC with the fronts on the front bowl, but I could be wrong. When I bench bled the MC, the front port pushed fluid throughout the entire stroke while the rear port seemed to stop halfway through. The front brakes are not dragging and don't lock up after a few braking applications(a sign of a residual valve), so i don't think it is plumbed wrong, but I could be wrong. I am at the point of thinking it may just be the bore diameter, which means i have to spend another $50 at the parts store for. I knew I should of just waited for a 1" bore MC. dang.
I don't have a pic, but it is a manual MC, it has a deep rod hole. The book says the stock Manual on that car has a 1 1/8" bore, but maybe the pedal ratio was greater, lowering the pedal pressure? That would make sense.
Raybestos #mc39177 74 chevy pickup 1/2 ton, (c10) 2wd NON power disc brake master cyl. Large bowl goes to front brakes>>>> I have used / sold hundreds of this master cyl for race car and general hot rod use over the last several decades. Always works well...If this # wont stop the car with minimal effort,,, then you have a leverage (ratio ) problem.. Good luck .. Dave
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