This created two unanticipated problems.
1) The new pedals I put in are out of a 71-73 top-loader car. I had trouble getting the rod comming through the firewall to line up with it's attaching point on the brake pedal. I have power brakes, BTW. Upon comparing the two brake pedals I found that the attaching point on my old pedal is 1.5 inches lower than the one on my new pedal. Needless to say I got the pedal assembly installed and brakes hooked up.
The problem is: since the attaching point is higher on the pedal is changes the leverage from the pedal and also the travel of the pedal. The pedal now has to travel twice as far. The pedal is also like almost 18 inches off the floorboard now. I can't get my foot on it without my leg hitting the column.
I can't figure out what is wrong. Obviously the problem is that the pedals ARE different. I thought it was a direct swap though.
How can I correct the travel of the pedal?
Do power brake and manual brake use a different clutch/brake pedal assembly (maybe i have the wrong one?)

2)The support bracket holding the pedals bolts to the firewall using the 4 studs from the brake booster. This means the firewall is sandwiched between this bracket and the booster. Here is the problem:
I think I damaged the master cylinder or boster in the assembly or dissasembly process. My power brakes are gone. I'm reduced to the "leg straining" manual brakes.
When the engine is running you can hear a loud Wooshing sound comming from the interior of the car. It is comming from the spot where the rod from the brake booster is comming through the firewall. It sounds like the loudest vacuum leak I have heard. You cannot hear it from the engine compartment. The soung goes away as soon as the engine is stopped and is not present when the engine is off and ignition in the run position. I am not familiar with how power brakes work.
I need som good advice here..
Do you guys think that maybe I put somthing back together wrong or didn't get somthing to seal?
Or does it sound like I damaged the brakebooster/master cylinder when I was reinstalling it and torquing things down.

Also the rod comming through the firewall is at a different angle now since it's attaching point is 1.5 inches higher on the pedal. The pedal moves freely so I know it is not binding. I don't know what is inside of a brake booster but i am thinking that somthing on the inside was not designed to work at a slight angle. Now some seal or somthing is damaged.

Any advice or information would be greatly appreciated. Thanks if you spent the time to read this long post.
-Justin

1) Thanks Don for the column.

2)NPD lists 2 different brake boosters/Master cylinders. Onw is for 71-72 1/2, and the other is for 72 1/2-73.

What is different between the two?

I was thinking maybe the my pedal was designed to work the earlier master cylinder/booster. If this is true it would be possible fix both my problems by putting a '72 MS/booster in the car.

These guys are right, the brake pedal is different between power and non-power brakes. It's all about travel and leverage. I found that out the hard way when I converted a 70 fastback to power disk brakes. I had the same problem...too much pedal travel. The thing would stop on a dime, but it was a weird feeling.

I always thought that the support bracket was the same for auto and manual cars. The pedals are different...the only difference was the pivot point for the pedals. It may be hard for you to see up under your dash. I have the support bracket out of the parts car because I took the steering column out. I can take a good look at it for you and send pictures. The parts car was a automatic w/ power brakes. Let me know.

I wouldn't try to use non-power assist with disk brakes. Disk brakes require a lot more pressure than drum brakes. You may find that it's hard to stop.

That sound from you booster doesn't sound good. You could try disconnecting the brake pedal and returning the rod to it's original angle to see if the weird angle is causing the problem.

I'm hoping that my 30+ year old booster still works. I have a complete power disk brake setup on the parts car. I would offer you the booster but I was thinking of selling the whole setup once I know that mine is working. Besides, the booster in the parts car is 30+ years old too.

Anyway... what route would be best to resolve the problem. I see two approaches.
1)find a new bracket and pedal assembly. I have never seen just the pedal for this year.. they are always sold as the entire assembly. This will probabally cost $200.

2)Take the brake pedal lever off my auto assembly and place it on the manual car assembly. The problem is that the auto brake pad is too wide. Fixing this would require me to grind the medal plate off both and rewelding the narrow one to the lever from the auto car. This lever would then go in place of the lever that is in the assembly now.

Don, how did you correct the problem when you converted to power brakes?

1)Take the brake pedal that went with my auto transmission, cut the foot pad off and weld on the narrower foot pad from the manual transmission assembly. This was the reccomendation by Will at modern driveline and it sounds like the best approach.

2)Sacramento mustang sells a conversion booster/MS for converting to power brakes. They have a kit for cars with a manual tranny. This kit comes with a brake pedal that they modified to work with their kit. This pedal is for use with the bracket I have. Unfourtunately their pedal only works with their kit.

To decide which route to go I need to decide if I need a new brake booster/MS. Method 1 is easier and cheaper, however if I ruined my MS/booster then method 2 will be better because I need a new booster/MS anyway.

Can anyone help me decide if I need to replace the MS/booster?
What could I test to verify it is broken... I already know the power brakes aren't working.

I think the booster is very important for disk brakes. Without it stopping is harder than manual drum brakes.

I would try grinding the auto pedal off and welding the manual pedal onto your original brake pedal arm.

Replacing the booster isn't that hard. To swap out the support you'll have to remove your dash.

Do you have a hand vacuum pump to test the booster with?

To me it was too big of a pain in the a$$ to go to all the trouble of tearing the car apart not to change both the assembly and the booster at the same time.

My only complaint with what I did is the clutch Z bar setup is not the greatest.

You might try Delta Bay Mustang in Brentwood Ca. It seems to me he had something he fabricated that might work for you.

This modification can be read in the Boss 302 Chassis book.....The Trans Am cars dont use a booster.

Cory

quote:

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Originally posted by TOPDowNMUSTANG:
I never really did solve the problem in my 70...I just kind of lived with it.

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quote:

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I would try grinding the auto pedal off and welding the manual pedal onto your original brake pedal arm.

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If you have the power brake pedal for an automatic trans then all you have to do is cut down the metal where the rubber pad goes to the size of the manual trans pedal.

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Ed S.