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Power or manual brakes.......again. UPDATE.
#1616222
05/05/14 04:24 AM
05/05/14 04:24 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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My 70 Charger had 4 wheel 10" manual drum brakes until 2001. I bought the car in 2000 and within a year I swapped in some 11" discs from a 75 Dart along with the MC and booster. I also used the OEM disc/drum proportioning valve from the Dart.
In 2006 I pulled the rear drums and installed a rear disc kit offered by Dr Diff. It consists of 10.7" Toyota vented rotors, Ford Cobra calipers with a 1.75 bore and a custom mounting bracket.
At the time I was running a '509 cam in my 493 and the 5-6" of idle vacuum made slow speed stops difficult. I thought that a switch to manual brakes would be an improvement. I figured that the stopping power would be equal to or greater than the power setup ever was.
Wrong.
I tried 4 master cylinders with different bore sizes. The biggest was a 1 1/4". I also tried a 1" and 2 different 15/16" units. Every one of them gave pretty much the same results: FIRM pedal but terrible braking performance. It was actually unsafe to drive over 20 mph and I am not an over cautious guy. I brake tested each MC and only once was I able to get the tires to skid. I weigh 195 and I gave the pedal everything I had.
I was baffled as to why the car wouldn't stop. I tried using different proportioning valves. I tried drum brake units, disc brake units....Each time I drove the car I got the same thing. I asked around to see if anyone had any insight. I didn't get much help then even though there were some suggestions. Finally I did what I really hate: I admitted defeat and put the power booster back on.
I want to try again. With my history still clear in my mind, what other changes should I consider to make this work? The smallest MC I tried was a 15/16" . My understanding is that a smaller bore would have more travel and require less effort. I tried both drum/drum combo valves and disc/drum prop valve. Neither were modified. Yesterday I read that Dr Diff suggests to use a gutted drum/drum brake combination valve. Could this have made the difference all along ?
Last edited by Frankenduster; 05/06/14 02:27 AM.
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Re: Power brakes vs manual again....
[Re: DAYCLONA]
#1616227
05/05/14 03:37 PM
05/05/14 03:37 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
I said it last time you posted your woes, you need at least 10 inches of vac for a stick car and 12 inches vac for an automatic, I suggested the vac pump but you didn't want it, I said try a vac resv canister at minimum.....bite the bullet and install the pump and a 70 B body disk master which IIRC is a 1" bore
Mike
I actually DO have a vacuum pump in the car now. Currently the system works fine. Its just that I still like the idea of having the simplicity and reduced weight of a manual system. The booster sorta makes the engine bay look cluttered as well.
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Re: Power brakes vs manual again....
[Re: Kern Dog]
#1616228
05/05/14 06:13 PM
05/05/14 06:13 PM
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Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,157
Mass
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Quote:
Quote:
I said it last time you posted your woes, you need at least 10 inches of vac for a stick car and 12 inches vac for an automatic, I suggested the vac pump but you didn't want it, I said try a vac resv canister at minimum.....bite the bullet and install the pump and a 70 B body disk master which IIRC is a 1" bore
Mike
I actually DO have a vacuum pump in the car now. Currently the system works fine. Its just that I still like the idea of having the simplicity and reduced weight of a manual system. The booster sorta makes the engine bay look cluttered as well.
If you want to hide the vacuum pump, mount it up inside the front fender, plenty of room
....I'd say the heck with the manual system, you want some stopping power, put a Mopar Bendix dual diaphram booster behind your current master (if it's a 4 bolt factory style), rid yourself of any proportioning valves or factory distribution blocks, run the rear brake line right off the master, front line just use a brake line Tee to split the lines L/R.....this is how I do my own 4 wheel disc brake set ups and customers, if you have a brake bias problem because the calipers weren't sized accordingly to produce a 60/40 front/rear bias minimum to an ideal 70/30 bias, then throw in an adjustable PV in the rear line
Mike
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Re: Power or manual brakes.......again. UPDATE.
[Re: Black_Bee]
#1616232
05/06/14 03:43 AM
05/06/14 03:43 AM
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Joined: Mar 2009
Posts: 2,464
Sydney,Australia
tex013
top fuel
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top fuel
Joined: Mar 2009
Posts: 2,464
Sydney,Australia
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its not just for ratio , the centreline of booster/ master cylinder is higher than a non booster master cylinder .
that is why their is different firewall plates booster / non booster .
just done this on my b body , booster to non booster and a customers b body - non booster to the bendix dual diaphragm booster
by the way mine had no firewall plate when I removed the booster
Tex
New best ET 10.259@129.65 .
New best MPH 130.32
Finally fitted a solid cam,
stepped it up a bit more
3690lbs through the mufflers
New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm
Power by Tex's Automotive
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Re: Power or manual brakes.......again. UPDATE.
[Re: Black_Bee]
#1616233
05/06/14 05:27 AM
05/06/14 05:27 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
Im not sure if you know this or not, but B-bodies had the linkage under the dash. Check this link:
http://www.piratejack.net/index.php?page...rt&Itemid=6
That linkage is what reduces the pedal ratio. If you skip using that linkage, you keep the stock manual ratio.
I was not aware of that. Thank you.
The firewall plate that is on this GTX booster looks different than the one on the Pirate Jack picture. PJs plate is sloped at the top, mine is square top and bottom. Now I need to look at some 68-70 B body engine bays!
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Re: Power brakes vs manual again....
[Re: Kern Dog]
#1616234
05/06/14 07:09 AM
05/06/14 07:09 AM
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Joined: Dec 2007
Posts: 18,157
Mass
DAYCLONA
I Live Here
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I Live Here
Joined: Dec 2007
Posts: 18,157
Mass
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Quote:
I apologize for not being clear enough. I mounted the vacuum pump in the LF wheelwell behind the headlights. It is well tucked away. I was referring to the brake booster at the firewall that looks sorta bulky. It is a Dart/Valiant unit with a standoff that moves it up and forward.
This dual diaphragm booster sounds interesting.....I guess I'll have to google that. Is this factory equipment or was it an "over the counter" Mopar part?
OK, I misread your post sorry  yeah that A body stand off booster is an ugly assembly, granted the dual diaphram Bendix isn't a petite unit either...but is factory correct for your Charger/year plus it's a beefy unit for power assist, day/night comparison to the single diaphram units, used and repro units are available, with the repros being "close" to accurate in appearance, function of the repros is fine though, should you go that route
Mike
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Re: Power or manual brakes.......again. UPDATE.
[Re: Kern Dog]
#1616237
05/06/14 02:07 PM
05/06/14 02:07 PM
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Joined: Jan 2003
Posts: 28,068
Irving, TX
feets
Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,068
Irving, TX
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The A body linkage provides no additional leverage. It's a 90 degree lever with the same length arms.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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