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Discussion Starter #1
Replaced the calipers, hoses, front lines, turned the rotors, master brake cylinder and the booster. My 69 C-10 goes to a "rolling " stop. With the pressure on the pedal it will not lock up or stop on a dime. The vacuum is 15 pounds. I am stumped on what to do next. It is no better than before I replaced everything due to age. Any suggestions what to do next? Oh and replaced the synthetic fluid and bleed the lines.
 

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Did you bench bleed the master?
 

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I know you said you bled the lines, but it still sounds like there is air in the system somewhere!
 

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Is the booster working properly? If you replaced the MC, is it identical in bore size and correct for disc/drum (if this is what you have) and not disc/disc?
 

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Discussion Starter #7
I have bled the brake twice. Bench bled the MC. Replace all parts with OEM disc front, drum rear. I have owned this truck since '88. Brakes were fine until the last few years. Driven very little, so I replaced everything and it is no better. Years ago they were fine when I towed my 69 Camaro. Engine is a mild 427. If vac is low, how to increase? Add an can?
 

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Minimum vacuum is 13 inches, from the reading I've done.
Some owners add a tank and a pump along with it.
Max assist will happen on deceleration.
Ride along with a vacuum gauge and get some readings during driving.
 

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Discussion Starter #9
Would a 8" Right Stuff booster make a difference. I have one on my Camaro with a 468 and the brakes work great, the rest of the system is stock disc/drum. Totally different???
 

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I would ensure the mechanical condition of present booster.
Does it hold a vacuum?
If supply is removed and plugged port on engine, does engine run better?
If it does run better, booster bad, leaky.
The smaller the diameter of booster, the shorter the stroke to MC.
But, 8 inch might work. Just be sure the rod extended from MC mounting surface is same as OE booster, rod screws in/out.
 

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I fail to see how a booster issue (low vacuum or not) can cause the problem of 'rolling stop' described. The booster will assist in effort, sure, but for not able to stop hard, the problem is likely elsewhere. With that said, I see you replaced the front lines. What about the rear lines and coupling hose? I have seen brake hoses collapse internally that have cause brakes to lock and/or not engage (depending how the internal collapses).
With that aside, I recently assembled the entire brake system (pipes, M/C and hoses) on my '67 w/synthetic and had a hell of a time trying to get the brake pedal firm and it would not 'lock', and believe me, I tried my usual hose in bottle method of bleeding and the hose looked clear of air. At the suggestion of a friend, I bought a pressure bleeder and I was surprised more air came out of the lines when I thought they were clear of it. It wasn't much air but enough to cause the wheels not to lock and also had a spongy pedal feel. Now, the pedal is high and firm and I can lock the brakes at will.
This is the unit I bought and I will never bleed brakes without it again :)
https://www.amazon.com/gp/product/B00CJ5DY16/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
As a suggestion, don't use the supplied chains to lock the pressure plate. I used two C-clamps (see attached picture) to snug the adapter plate down and used 20PSI from the compressor. I didn't use the tank to supply fluid. I topped off the M/C after each line was bled because I didn't want to risk having any mess.

Mike
 

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I just went through the same thing with my sons 76 Camaro. Replaced all parts and you had to almost use both feet to get it to slow down. We bled the brakes, adjusted the rear shoes, nothing was helping. I checked the booster by pressing on the brake then starting the engine, the pedal would move down some like it was suppose to. I teed my vacuum gauge on the booster hose and it had 18 inches of vacuum. Shut the engine off and it held vacuum. I did research to further test the booster. Wtih the engine off one press of the pedal should drop vacuum 5 to 10, mined dropped about 15. I took the old booster and hooked it up just under the hood and worked it by hand to see what it did. It didnt have the master cylinder on it. I got my 18 inches of vacuum on it and then pushed the rod with my hand as hard as I could and it only lost 4 inches of vacuum. So I was going to install the old booster on the car and see how it did. I removed the new one and when I got it off I though I would just hook it up under the hood with no master cyl. I worked the rod a few times by hand and I think being able to move all the way without the master cyl on it changed somthing inside the booster. With my 18 inches of vacuum on it, it only went down 4 when pressed. I reinstalled the booster and we have great brakes with a light touch of pedal.
 
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