Discuss 1968 Mustang Brake problems on AllFordMustangs.com, the place for Mustang enthusiasts.
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I have been thru all of your problems. Let me ask you did you change the brake pedal to a power pedal and if so was it a 67-69 power pedal? This is important. Second are you using a brake booster for 67-69. Because there is a difference in the 70 booster. The way you can tell the 67-69 booster pushrod where it connects to the brake pedal has a curved end unlike the 70 which is straight. Also the 67-69 bendix booster has a spacer plate on the backside which sets up the pedal height. The 70 booster is also different. You CAN NOT interchange any of these parts even if they seem to fit. This is why you have low or touchy brakes. The disc brakes from the 70 donor car are not the problem. For safety reasons you want to get a combination proportioning valve. A proportioning valve does not cause touchy or low pedal brake problems. Its only purpose is to control how much fluid and pressure to the rear/front. Hope this helps
Just wanted to give you the list for the correct parts: 1-67-69 power brake pedal, 2-67-69 power brake light switch, 3-67-69 bendix booster with spacer and master as a unit, 4-combination proportining valve. Make sure that you have the correct brake pedal mounting bracket. This will solve your problems. Also if you want to see the correct parts go to MustangSteve FAQ- brake pedals
All the components I have are 1970 components i.e brake pedal, switch, m/c and booster as well as all the brake calipers cylinders and distribution block. I would assume that all these together should work properly which should avoid me having to step down to a 67-69 set up.
I will look into you suggestions though to see what i come up with
I read all of your post again. Do you have a bendix style booster with the spacer plate on the back or the midland booster with the band around it and spacer on the front? Why I ask because the midland booster has a spacer that mounts right behind the master cylinder which might explain why your booster pushrod is to long. You have to make sure you get the correct setup. 1-1970 bendix booster with spacer on back,disc/drum master or midland booster with spacer on the front,disc/drum master. 2-recheck brake pedal, it should be 4.5 inches from pivot mount to brake switch mount(center to center) and correct mounting bracket 3- possible that you have reversed or crossed brake lines(the larger bowl in the master goes to the front) 4- get a good combo proportioning valve. Got mine from NPD,part#2b091-20ba
Also did you enlarge the hole in the firewall where the booster mounts? A car that came from the factory with drum/drum setup was different than disc/drum. The hole thru firewall is about 3/4 inch higher with the disc/drum setup. You still go to MustangSteves FAQ brake pedals and see all of the correct setups.
I am using the Bendix style booser with spacer plate. As far as pivot point i will have to measure it. I never changed the hole on the firewall since it seemed to fit correctly. I will look into you suggestions
Also check your vacumn. You should have the booster vacumn line hooked into the tee that is in the manifold not in the back of the carb. You also have to have a minimum of 15-17 psi pressure for booster to work correctly.
I am just about to install a new brake booster on my 68 Mustang all drum brakes and found out here in the forum that there is a big difference for the pin positions with manual brakes vs power brakes. The pin position effects the amount of travel and pedal power while applying the brakes. A power brake pedal is also needed to complete your swap.