Vacuum vs Manual brakes

TType85

Well-Known Member
Joined
May 25, 2001
I am having some issues with my vacuum brakes and am trying to decide if I should go to manual.
The car currently has:
1" bore Blazer MC
11" B-Body Booster
G-Body vacuum pedal
Disc/Disc prop valve.
C6 J55 (Z51) calipers [2 piston front, single piston rear]
C6 J55 (Z51) rotors [13.4" front, 13" rear]
Stoptech Sport pads (coeff. ~.4)
Stainless caliper lines and drop to axle

Right now the brake pedal has about a 1" of movement before the brakes start to engage. Once you get to the engagement point they stop the car great. It's not mushy and if you let off and hit them again, it's the same. The brakes have been bled like 10 times, no leaks, all calipers have the bleeder at the top. The master was bench bled plugging the ports. I would really like to figure out what is causing this or if it is just normal. All parts are new except the pedal. Adding 2# residual valves was suggested.

Even if I fix that 1" of travel I have a few other issues. I want to AutoX and use the car for HPDE stuff so my concern is actually having brakes when I need them. I know you can use a vacuum pump or external revivor but that is adding more points of failure and cost. I also don't know how fast something like a "brake bandit" can recover the booster. I thought about hydroboost but the PS pump is already going to be taxed with all the turning plus it adds a lot of complexity and cost to the system. Manual brakes are cheap and simple at the expense of "comfort".

Doing some asking around and some calculations; a 24mm bore master seems to be the choice along with a 6:1 pedal ratio and a more aggressive pad like EBC Yellow Stuff. I like the TRZ bracket that makes the master level or there is the kit from manualbrakes.com that I can get everything (except the pads) for $200

Anyone have any input or suggestions/experience on this? The car is not a daily driver.
 

Mark T-TB

car crazy from birth
Joined
Apr 6, 2009
(FWIW) My "little green car" came from the factory (U.K.) with vacuum/power brakes.
When I got the car it did not have the booster... just a very "firm" pedal. I drove it that way for a lot of years.
Later I changed to a different master cylinder - for less pedal effort - and am pleased with the results. Brakes were fine for auto-x. I wished that I had made the change sooner.
I'd bet that anything Andrew (Turbo6inKY) recommends would be well thought out and proven.
Good Luck.
 
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