Slick 60's

hey gang,i have a problem and was wondering if someone on here could help me out.i will tell you what i have.i have a 1965 ford truck 2wd shortbox.
i updated the motor with 302 auto trans.i updated the brakes from a 1978 ford with power brakes.disc in front and rear drums.the problem im having is that when i put on the brakes they are so touchy that they put your head threw the glass when you stop.i do have a porpotioning valve on it and i also adjusted the back brakes up to equall it out,but nothing seems to work.any ideas??please!!!

Did you cut the master cylinder rod to the pedal to the correct length?

i think it might be to tight with not enough free play because i know its really close to it.do you know how much free play the rod has to have?

O/T, but I like your Avatar. I'm a High Life man myself.

Possible causes:
1. Brake lines routed incorrectly, fronts to rears etc. Make sure the front well on the master cylinder feeds the front discs. Do you need a diagram for the proper routings on the lines from the proportioning valve?
2. Old rubber brake hoses. They swell internally and retain internal pressure. It is impossible to see this form the outside. Did you use new lines, or the originals harvested from the donor truck>
3. Brake pedal height. If it sits too high, you have more than the normal leverage to actuate the brakes.

Hope this helps.

yes if you do have a diagram that would be great.also all new brake lines with about 10 miles on them.also the brake pedel is the original from the 65.
also would it matter on the master cylinder with the brake lines?

Gritsngumbo wrote:O/T, but I like your Avatar. I'm a High Life man myself.

Here is the link to a thread with the pictures, thanks to Fanatic:
http://www.fordtruk.com/forums/viewtopic.php?t=23195

I assume you are using a dual reservoir master cylinder from the '78, as well as the proportioning valve, correct?
Did you use new rubber brake hoses?
Are you using anything not standard to the '78 brakes setup (other than the original pedal)?

yes everything is new or used from mid to late 76,77,78 ford truck.the only im using from the 65 is the brake pedel.brake lines and hoses and master cylinder all new, disc brakes in front with new calipers and new rear brakes shoes and rear spring kit and new wheel cylinders.the power brake booster is used along with brake propotioning valve.i also looked last night and to check the brake line hook up and i have the big master cylinder port that is right next to were the master cylinder mounts to brake booster goes to the front and little one in front of master cylinder goes to rear.

Does the brake pedal from the later donor truck have a different pedal ratio? Most factory power brake applications use a different ratio (more distance between pedal pivot and the pin that connects to the booster rod).
I am not familiar with the later trucks but maybe someone else knows.

As far as I know there are three issues that could possibly cause it (in addition to others already mentioned)

Master cylinder piston smaller than required. The later trucks used a larger diameter master cylinder. A smaller master cylinder bore requires alot LESS pressure to apply, so the booster assist will tend to over-apply the brakes.

Wrong pedal ratio.

Booster internally damaged. This is probably the issue if you have the right geometry and the right mc.

I've done this coversion a couple of times. I had to fill in the original hole in the brake pedal lever and re-drill to get it to line up with the right free play. If I recall correctly the new hole is a little farther back and higher on the arm than the original.

New hole for the booster pin on the brake pedal should be LOWER, giving less mechanical advantage, rather than higher. Having it higher will make for a mushier pedal and more mechanical advantage and that tends to make the brakes really touchy.

well if i remember right, i think i redrilled the hole right behind the original hole in the brake pedal arm to fit it the first time.so if im understanding you correct,i have to redrilled another hole below the original hole that was there?

If it lines up with the booster rod where it is, do not move it as changing the angle of the rod can cause booster problems (like really touchy brakes, when the valve internal to the booster breaks.)

Did you weld up the old hole? Hopefully you do not have two holes one behind the other, as it might weaken the pedal.

It would be best to check the pedal out from a truck same year as your booster to see the dimanions on it, then match that.

yes the hole lines up perfect and as you said moving the rod at a angle will give me (touchy) brakes,i already have that problem,if it got anymore touchy i wouldnt even use the brakes!i dont have the pedal from the original truck to note anything.this truck has been done over a year and i just drove it like that the way it was but the problem is,i restored it for my wife and she wont even drive it because its just not right and to dangerous as it really easy to put your head threw the glass.so it pretty much sucks doing all the work to restore it and to scared to enjoy it!

have you checked the pushrod length between the booster and master cylinder.

i dont know what it suppose to be?does it suppose to snug,loose and if so how much?

Pushrod should be about 0.010" shy of touching the mc piston at rest.

It sounds like you have a booster with an internal valve broken. It can cause the symptoms you stated.

ok,well thanks for all your help and hopefully i can find the problem.