Brake problem let me know your thoughts

[benno505]

Hey guys,

got a 68 charger has 4 wheel wilwood discs and 4 piston calipers. has stock style right stuff booster and wilwood tandem master cylinder.

I have always had not the best of brakes due to not getting much vacuum to them from carb never being properly tuned and a big cam (300/305).

i recently had the diff out modifying some things and put it all back together and i was bleeding the brakes. my wife was in the cab pressin gthe pedal for me then bam the pedal went to the floor, i got in and had a look and the I bolt that bolts to the pedal and screws into the booster rod bent in half (yeh i know right, its a 12mm bolt and my wifes not that strong).

So i removed the bolt straightened it and strenghtened it.
so i take it for a drive and like i said i have never really had good brakes but not when i put the brakes on slightly you can feel it starting to pull up but if you need to brake suddenly i have to put neally every bit of strength i have on that pedal and it will start to pull up but will not even lock up, almost like it moves down about an inch then feels like trying to press against a brick wall.

i do not have a very good vac gauge but i know it is really low, but before i start tearing every thing down i.e booster and master cylinder what do you guys think it could be? any help or ideas would be greatly appreciated.

[no go nova]

Go to manual brakes or hydro boost style system. Maybe a electric vacuum pump could help. Also make sure your master cylinder is the correct size and you have a disk/disk proportioning valve.

[benno505]

thanks, yeh got disc disc prop valve

[Apogee]

It sounds like a vacuum boosted system without any vacuum to power it, just like you suggested.

Post up exactly which Wilwood calipers you have (p/n) and/or their piston area, along with the bore size of the master cylinder you're using. Also, ;et us know what size (diaphragm diameter) and configuration (single, dual, etc) of brake booster are you running? The booster may not matter since it sounds like you probably have single digit vacuum levels anyway, but a quick test of the booster should tell you whether it's contributing much, if anything, to the braking equation. Start the car, warm it up, turn off the ignition and then apply the brakes multiple times to clear the booster. Apply the brakes firmly and start the engine, the pedal should noticeably drop as the vacuum assist kicks in. If it doesn't, then the booster is probably getting in the way more than it's helping.

Tobin
KORE3

[benno505]

It sounds like a vacuum boosted system without any vacuum to power it, just like you suggested.

Post up exactly which Wilwood calipers you have (p/n) and/or their piston area, along with the bore size of the master cylinder you're using. Also, ;et us know what size (diaphragm diameter) and configuration (single, dual, etc) of brake booster are you running? The booster may not matter since it sounds like you probably have single digit vacuum levels anyway, but a quick test of the booster should tell you whether it's contributing much, if anything, to the braking equation. Start the car, warm it up, turn off the ignition and then apply the brakes multiple times to clear the booster. Apply the brakes firmly and start the engine, the pedal should noticeably drop as the vacuum assist kicks in. If it doesn't, then the booster is probably getting in the way more than it's helping.

Tobin
KORE3

thanks and sorry for late reply

front brake are 4 piston 2 piece 12.19" rotors (wilwood forged dynalite) part no. 140-11547-R
Rear brake are 4 piston 2 piece 12.19" rotors (wilwood forged dynalite) with internal park brake.
7/8" bore dual tandem master cylinder
wilwood 4 port prop valve
right stuff detailing brake booster 8" Right Stuff Detailing Brake Boosters RPB8001
started the car with pedal on and it barely moved.

what would be best option to get them working for now and future will be a hydroboost?

[Hydratech®]

A very well known TV show just went through this exact same thing. Their group had just built a '68 Coronet that would not stop properly and needed an immediate solution that would definitely take care of business. They had installed a typical popular 4 wheel disc brake package, a 7/8" Wilwood MC (that conventional / internet wisdoms would tell you *should* apply enough pressure to them), and just could NOT get the car to stop. We were delighted when we received the call, (and we tripped all over ourselves and pumped a system out for them ASAP as a courtesy as per being big fans of their show)... They installed our Mopar B body brake assist system # 3673-BASE with a larger Wilwood power brake spec 1 1/8" bore MC. We sat back with enthusiasm as to what they were about to experience...

72 hours later they let us know that it wasn't just better, it was a MONUMENTAL improvement on the '68 Coronet. I suppose that all that aside, the best came to pass a short few days later when their group contacted us yet again for a '71 E Body they are building (featuring a 2015 HELLCAT 700+ horse powertrain) and that they also wanted our wares for this beast too (so yes, we tripped all over ourselves again to punch out another system for them on this build too)(Mopar E Body system 3670-BASE).

It is interesting that whenever I say it, it always comes off as "blah blah, sales pitch, blah blah blah, sales pitch, sales pitch". That being said, how about a customer testimonial from well over a decade ago? Hearing it from somebody else that took the plunge is something I always look for as a consumer - especially if it even remotely sounds too good to be true (!).

108197

Most people expect things to essentially work, though we smile in the notion that our wares ALWAYS vastly exceed customer expectations. There are forum entries out there that document the installation of HYDRATECH hydraulic assist systems as the TOP 3 MODS they have ever done to their car. I am a very conservative individual that does not like to ever beat my own drum, but I have grown very weary of talking to thousands of people over the years that have tried everything known to conventional wisdoms to get their muscle cars to stop appropriately and responsibly by comparison to how much horsepower they are packing. Why? I was hit by a car as a young boy and was lucky to even remotely survive. I was within an absolute inch of my life (mangled very badly), was coached that I was not going to be able to live a life like all of the other boys moving forward. What if that '72 Grand Prix could have stopped just that much faster? My left leg is an inch shorter than my right leg, and things hurt like hell all these years later...

Interesting that I am now the owner of Hydratech Braking Systems all of these years later too, always working towards helping muscle cars stop better than ever. Yes, that is "TMI", but it IS the absolute summary point of why I do what I do.

There IS a difference - Thank you for choosing Hydratech!

[benno505]

Hi Paul,

thank you for your post, I actually requested a quote from you about a year ago. and I will definetly be putting in a hydratech system in the future but for the time being I simply can not afford one with us building a house at the moment and my son starting college.
is there cheaper fix for a marginal improvement for the time being? you mentioned a larger master cylinder?

[Hydratech®]

Hi Benno - A vacuum reserve tank will help a little bit (but only a bit) - here is an example item:

http://www.summitracing.com/parts/crn-99590-1/overview/

These can at very least accumulate the higher levels of vacuum your engine can produce at higher speeds when you let off of the gas / downshift). Let's say you manage to pull a 20" vacuum in the tank, note that it's only good for one brake apply though...

Do not waste your time on auxiliary vacuum pumps - they truly suck (no pun intended). If you want to prove out what extra vacuum will really do, grab a 25' section of vacuum rated 3/8 hose and connect one end if to your wife's (?) dead stock car (to provide high vacuum), then connect the other end to your vacuum booster on your muscle car. Back up a few feet, then pull forward a few feet (as the hose length connected to the other car allows) and see if you brakes actually feel dramatically better (OR NOT). If your brakes feel like a million bucks with the artificial vacuum supply provided by the other vehicle, I'll be surprised (though it will tell you whether or not more vacuum is the actual issue).

Replacement brake pads with a dramatically higher coefficient of friction (meaning WAY more bite to them) will also help - Tobin at Kore3 will be helpful here to cover this (or contact Wilwood directly telling them you need the most aggressive pads available for your specific brake package part numbers). They are short lived, are going to dust like all hell, and may even wear your brake rotors considerably, but they will provide a higher level of available brake torque (real time braking) for the same amount of pedal effort / line pressures available to your calipers. This is actually the best answer for your scenario in my opinion (for now).

The only other bandaid that comes to mind would be to go even smaller on the MC bore size (from the small manual brake bore size 7/8" you are already currently running). The larger you go on the MC bore size = the harder you will have to press the brakes to stop (and therefore vice a versa)(simple hydraulic leverages). You will have a longer pedal stroke with a smaller bore MC of say 3/4" versus the 7/8" MC you currently have installed, though it will generate higher brake line pressures to your calipers for the same amount of pedal effort applied (once again at the expense of further pedal stroke). I don't recall for certain, though I believe the '74 - '75 Chevy Vega (Monza?) ran a 3/4" bore master cylinder you may be able to temporarily cobble into place without too much trouble.

$565 gets you into the brake unit:

http://www.hydratechbraking.com/Mopar_B_Body.html

Yes, you would still have to come up with some power steering lines to connect it up, though that seems like an area where you could get by through working with a local hydraulic shop if needed to bring some basic plumbing into existence at lower costs. Oh yeah.... I just remembered that you are on the other side of the planet though (Australia), and realize that you are also faced with $168 US Postal Service Shipping costs. I'll never forget the Aussie that tried to smuggle one of our systems back home in his carry on luggage a few years ago after his visit to the US! The TSA and Customs called us - let's just say it wasn't worth the poor blokes troubles! :hammer:

I do know what it is like to be in your shoes - the answer right there in front of you, but LIFE is in the way from just buying it. Realistically, you have made it this far with brakes that suck. Any further money spent on bandaids may just being taking more or your time and money further away from the answer? Tough call - a few smaller expenditures will help some, or wait until you can nail it? Bending a brake pedal rod connection bolt at your brake pedal makes me think you should be downshifting more!

:cheers:

[benno505]

yeh thanks Paul,

that reminds me when I bent that rod I was actually just planted it and was coming upto a intersection and the pedal went to the floor had to drop it 2 gears and she locked up, just lucky there was no cars coming the other way.
I will just have to put up with the brakes until I can afford your unit, thanks for the help