|02-05-2012 10:31 AM|
The distance of the hole from the point that the pedal arm hangs from , the lower the ratio and higher effort required to apply the same amount of force. Its another lever and fulcrum setup, so look it over.
|02-05-2012 10:01 AM|
|02-05-2012 09:47 AM|
|02-05-2012 09:18 AM|
as soon as I read the dual booster, I listed the pushrod..
thats the #1 issue when changing to those
|02-05-2012 08:51 AM|
Oh and to reply to the original post, to stay on topic here, I just ran into the same problem with a 1970 impala w/a 502 .
Pretty much the same setup too, gm front disc and calipers, wilwood rear calipers and rotor kits on a 9 inch ford rear ( Yeah..how bout it?)
dual diaphram 7 " booster, new master etc etc etc.
Seems the biggest problem was the same , inability to apply brakes hard enough to lock them up.
Turns out the pushrod angle on the brake pedal was not at the optimum 90 degrees when pressure applied was sufficient to stop the car/slide the tires.
anything more or less than 90 degrees will diminish the ability to apply force as it changes the pivot point or fulcrum which.
Seems the original installer had to mod something under the dash and ended up with a pushrod that was too short. It was about 1 1/2 inches too short.
Once that was fixed the car would skid the tires if desired.
The 7 in dual diaphrams work pretty well. We checked the vacuum supply and it seemed low (14 IIRC) due to the radicalness of the cam,but the booster was not the issue.
Dean oshiros article also clears up the power brake-non power brake master cylinder truths--myths whatever you want to call it. It points out the facts like master to slave (w/cyl or caliper) bore size to bore size ratio importance , application requirements for drum or disc, etc etc etc etc etc etc .
|02-05-2012 08:37 AM|
I would be interested in Knowing the final outcome of the deal.Post something in the lounge if you see anything, if you can.
|02-05-2012 08:00 AM|
Good article, questionable guy to deal with based on this posting.....
|02-01-2012 05:07 PM|
Read through this Gonzo. I do every now and then , I still have a lot to learn.
Dont spend any money untill you read this. I am sure something will come to light.
The info you want is at the right of the page, under brake article, read them all.
|02-01-2012 08:40 AM|
I had a similar brake problem on my '52 Olds custom It is subframed with an '87 Buick Regal sub, disk brakes. The rear is a late Chev drum. Seven inch dual chamber booster, Corvette master.
The problem was solved with an electric vacuum pump. The brakes on the Olds now react very much the same as on my late model Mercury Gran Marquis. Just light foot pressure is required. I still do not lock up the brakes...it just stops!!!
|02-01-2012 08:38 AM|
|02-01-2012 07:58 AM|
whats the engine vacuum?
is the vacuum line hooked up under the throttle blades..??
is the pushrod used, the correct one for that boooster..?
was the booster and master a matched set??
is the master a manual master.. ?
is the masters bore size correct for the calp. bore size..?
do you have a 4 w disc master..?
did you clean the rotors and pads.. or are they full of oil/grease?
my bet is lack of vacuum.
|01-31-2012 09:07 PM|
|01-31-2012 08:26 PM|
81 camaro doesnt stop worth a darn, even with wilwoods
so here's what i got: wilwood d52 dual piston calipers(front), wilwood gm metric single piston(rear). new master cylinder bench bled twice, new disc/disc prop valve, new dual diapragm (7" i think)booster, stainless braided lines, new steel line all 'round. lines have been bled seven ways to sunday, pedal goes about 1/4 and gets firm but brakes suck. car stops but i cant for the life of me lock 'em up. they just slide to a stop. i dont know how to check psi on the calipers. i don't know how to measure master bore. the back of it that mates to the booster is about 1 1/2" diameter. my old one was a lil smaller than 2". almost as if the pressure isnt up to par. vacuum is about 20 inches and drops to 13-15 when braking. tried an old overflow tank to act as a vacuum reservoir but without a check valve i don't think it works right. any good ideas out there? i'm kinda broke so i'd rather not gamble on a new master if i dont have to. thanks in advance