I got an issue with my brake system. I'll tell you what I got. 82 Dodge booster and MC with a 71 Dodge rear drums and the stock 55 Desoto drums up front. It feels like the booster is bad or not getting enough vacuum but the booster came off of a daily driven truck and worked when I removed it. However my pedal is rock hard. Do I need a proportioning valve for the rear?? Help summer's coming.
i don't thibk your problem is a lack of proportioning valve,,,,,i think partially it's your master cylinder choice. you have drums/drums...is you M/C for disc/drums? what about the residual valves? are they in the M/C or did you put some inline? what is the bore of the master cylinder? what is your pedal ratio? i'd ditch the booster and just use a plain manual brake cylinder...like a `67 ford mustang drum/drum....it has a 1" bore....your bore may be too large
so it isn't wise to use a disc/drum booster and cylinder on a car with all drums, huh. what's the story with that, exactly? would it still be cool if all the bores matched up, even if the booster/MC was for discs on the front end?
yes and no...master cylinders for dics brakes CAN have very big bores because disc brakes need more volume of brake fluid..(the bigger the bore,the more fluid is moved for the travel of the piston inside the M/C). so,if you put one on a car with dums brakes with small bore wheel clyinders you can end up with very little pedal travel . put on a master cylinder with a very small bore and you will get too much pedal travel master cylinders for disc/drum usually have one fluid chamber larger for the disc's and a smaller one for the rear drums. master cylinders for drum/drum usually have equal size fuild chambers he mentioned the master/booster came off a truck.....i'm thnking it's huge. that's why i asked about the spec's of the parts used....things have got to match up to work properly
36 is right, you CANT start to diagnose this prob w/o all the wheel cyl bore diameters as well as the MC bore diameter.
hmmm. maybe mine will work then. the MC and booster i am going to run is from a 71 pontiac, and has either 1" or 1 1/8" diameter to the bore. the factory pontiac wheel cylinders up front and the 93 buick units out back are all 1" diameter. the factory MC was actually larger in bore than the wheel cylinders, i assume to ease pedal pressure. interesting. any other idears?
If the master your using is disc/drum and you are running all drums, you should install 10lb residual pressure valves on the front lines to keep the shoes from retracting all the way back,resulting in a low pedal.Ive got this problem on my 64 falcon, have to put the valves in soon, i almost hit the floor on panic stops!!
Well on the dodge truck the MC came off of, they use a separate proportioning valve so there shouldn't be any built into the MC. I have the 10 lb residual valves but I didn't install them because I thought they were really only needed when the MC was mounted below the wheel cyclinders, which mine is firewall mounted. The MC I believe is a 1 1/8" bore. I thought that it may work because on the Desoto up front there are 2 wheel cylinders per wheel thinking they would require more fluid like a disc. I am not certain on the bore size of the wheel cylinders. The ones on the rear are from a Challenger and look to only be about an inch. If I hit the pedal hard enough the fronts will lock in the gravel just before the rears.
no answers for ya, but i just put a power booster, dual master cylinder set up from a 78 corvette in my 60 catalina which is running drums all the way around. i put 10 pound residuals inline to the fronts and rears. the pedal travels pretty far, but it stops great. i think i still need some tweaking though. you're getting way more help than i did. i asked and asked about setting this up, and didn't get help so i just did it.
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