Not too long ago I purchased a disc brake conversion from ssbc which I have never gotten to work right due to a vacuum problem with my big block. Which in the beginning was fine between 10 and 12, now they say I need a min. of 18"'s. Jerks. Anyway can I just purchase a manual master and junk the booster, or what other alternative would work to get the brakes to function properly? Vac. cannister, anyone had luck? Old question.
Question Just changed from manual to power. would not change back for anything. Have you installed the kit and having trouble with power assist from the start or on the second imediate brake application ? Hows your rear brake adjustment? How about your Engine, Is it stock and in good mechanical condition ? Any engine missfire or have you checked for vaccume leaks, cylinder compression ? Are you running a large performance Cam ? have you checked the engine vac at several ports below the carb throttle plate and intake Manifold ? Please tell us a little more about the engine and current brake set up.
It seems I have had problems from the beginning. Hard to tell though. Swapped out the SBB for BBB at the same time along with suspension, rearend, drivetrain, etc. I have bench bled a couple of times, bled the brakes several. It was a swap from SSBC to get rid of the drums up front (std $895 kit), but still running drums in the back. It does have a proportioning valve installed toward the rear. That all seems set. The power booster seems to hold vac. cause when you disconnect the vac hose you get a rush of release. The engine is new with 10:1 compression, a mild cam (not real wild, very streetable). Checked vac at several ports on the SP1, same vac everywhere, 10 to 12"'s. A little more at the carb. The brake pedal seem to be set correctly, but this is the first time dinkin' with the plunger. The car will stop, it just does not feel like there is any power assist. I called SSBC, got "0" help. Not real impressed. Any help, or thoughts would be appreciated. Really at the end of my rope with this one.
I've never installed one of those kits so I am not the best one to respond. But since no one else is chiming in, does the kit come with a new disc brake master cylinder? Also, I don't know the answer to this question but is the pushrod length the same between a power drum brake system and power front disc brakes?
SSBC kit yeah, basically it comes with everything. "GM kit features: Single piston calipers, 11'' vented rotors, CNC machined mounting brackets, pads, hardware, adjustable proportioning valve, adapter lines, mounting hardware, 7'' booster/dual master cylinder (optional), flex hoses, seals and Timken bearings, stainless steel grease caps and new spindles with cast in steering arms. Includes easy-to-read instructions and a 10 year warranty." It was easy, just not working so I am wondering what I did wrong if any?
Your new booster has a 7" diameter diaphram. What is the diameter of your original booster, I believe it is significantly larger. Your mechanical advantage (pedal ratio) has not changed so you would expect less power assist from a smaller diameter booster. You can do the math, 3.14 x radius squared. Maybe you need to get used to the new feel. How does it stop? Hopefully there is someone on this board who has installed the same kit so they can share their experience.
Booster Well we could start with eliminating the booster, I Think the factory is a 11". When I did my disc power brake conversion the first Booster was bad. With the engine off and Booster vac. up, pump the Brake peddle you should possibly hear the vac. bleeding off under the dash slightly with each push of the peddle. After the vac. has bled off with several pumps the peddle should feel harder when pushed. Next push down on the brake peddle and hold then start the engine. The peddle should drop some as the engine vac pulls on the Booster. How much, mine goes about 1" If it does not the booster may be bad, but you need to eliminate low vac as the cause before condemning the booster. Just an idea, may sound kind of crazy, but if you don't have a Air condition vac. pump to connect to the booster direct with a Gauge and valve to regulate the vac. It would let you build up the booster vac fast to specs.18" push the peddle and test for a difference in operation. Or you could pull another car up next to yours with the correct vac. required. Run a hose from its engine to your cars booster and with the other car running try your brakes. use a long enough hose to move your car back and forward several feet to try the brakes. LOL . I know it sounds crazy but it would work. Normally I would just do the vac. bleed off test and if it failed I would replace the booster. But you have so much time and money in the brakes. I would eliminate the vac. You also really need to make sure you always have slight peddle rod play to booster. Also that the booster rod is not compressing the master cylinder. If this test works you need to look at engine vacuum
Similar problem Had the same problem with my 84 Regal (already had front disc brakes from factory) with a then 427 Chevy motor with a 714" lift camshaft. Tried a Vac can with no results. In the end I put a Grand National master cylinder (the one with the small elect motor on the bottom of it that makes its own pressure) and now it will throw you through the windshield. There not cheap new (I paid $500.00 at the Buick nationals for it) but you can shop around and get a used one much cheaper. If you decide to go that route you will also need the plug in wiring that goes to the switches on it. Hope this helps
As a last resort, there are aftermarket vacuum pumps avail to run your power brake booster. Diesel- equipped cars also used electric or hydraulic assisted brake boosters. I'd follow Freakazoids suggestions and go from there....
Which hole in the brake peddle are you using? There should be two, the upper one is for manual and the lower is for power brakes.
Can't remember, will check along with what Freakazoid was talking about. Anxious to see if this may be an easy fix. Hopefully.
