Power Booster Install questions

[Flatbed136]

Swapped out the manual brakes on my 68 C20 with a power system and have a few questions.

On the threaded rod that attaches to the brake pedal, how far should the piece with the hole in it be screwed in or how many threads should be exposed?

For example, when I pulled the manual linkage off, there were only 3 threads showing from the top of the nut to the rod its self.

On the brake light switch:

Will turning the adjustment nuts to the right bring it down to the pedal?

Don't mean to try and beat a dead horse but I didn't find what I was looking for in the two pages of post I looked through.

The brakes work well and it sure beats the manual but I don't think I have the piece screwed on to the rod far enough to be deemed safe so wanted to double check. The way it is now, there are quite a few threads showing.

Thanks

[dave2953]

When I did mine, I had four or so threads threaded into the piece that attaches to the pedal, and it backed itself out. I am using a non-factory setup though ('89 burb) I am having to rethink the setup and either integrate some type of locknut like the factory pedal had or switch it out altogether. I had to tweak the brake light switch on my truck quite a bit to make it function. If I'm not mistaken, as you are sitting in the truck, turning it counterclockwise will bring the pedal towards the the toe pan. Is this what you are asking?

[JimKshortstep4x4]

The rule of thumb that I have always used for depth of thread is 1 1/2 times the bolt diameter. Since the rod is 3/8" then 3/2x3/8" = 9/16".

Jim

[cparman]

The threaded rod under the dash is JUST for pedal height, only. Make that adjustment to allow you to get the brake pedal height where you want it. If after that the pedal seems low, then you need to adjust the clearance between the booster and master cylinder. Search my posts about this. I have done a bunch of this, and IMO my way works well. HTH

[PanelDeland]

Flatbed,the power brake rod is longer than the manual one.I don't know how much .Mine was a kit so it came with it and I never measured.

Actually IIRC the threads on a standard nut fully threaded is at max strength.The thread surface area is supposed to equal the pull or tensile strength of the rod/bolt or stud it's threaded onto.It's been a good while since I took the class on that though.

[Flatbed136]

Thanks for the replys.

In regards to the brake light switch:

As it sits now the brake lights are always on so I'd like to know which way I need to turn the nuts to get them to go off.

I read that it can be a bear cat to do, so I thought I'd ask and save myself some cussing.

In regards to the pedal height:

As you guys know, with the manual setup, the pedal was equal with the clutch pedal and both rested againest the rubber stops.

Maybe what I should have asked is what is the proper pedal height or something along those lines.

One thing I noticed too was when the truck is off and I push on the pedal, it isn't a smooth trainsition down. Press down and it starts to go down but than as you go farther it seems like it is stepping down and than goes back to a smooth transition the rest of the way. I probably didn't explain that very well but hopefully it strikes cord and you guys can understand what this newbie is saying.

Just want to make sure I have everything right. Should would hate to have to ditch the ol' girl.

This wasn't too bad of a process since I really didn't know what I was doing. Now if I can get brave enough to try the power steering install.

Thanks again for all the help. It is greatly appreciated.

[treveiger]

Interested also

[Flatbed136]

I read your post cparman on how to adjust and that is a clever way of checking.

Once I get the rod/pedal height squared away, I may have to check that.

From the replys I got, I have the rod threaded too far out so hopefully when I fix that, I'll have less pedal travel etc.

I'll get at it day and see what I come up with.

Thanks again

[Flatbed136]

Based on the information I got, I went ahead and measured the amount of threads and got as close to the 9/16" mentioned.

Also are some views of the pedel height with the linkage set at the 9/16".

I also have a pedel extension but didn't know if I needed to use it or not. It almost appears I would have to to get the pedel back up higher where it was with the manual.

Thanks again for the help and hopefully the pics will help a great deal in determining what I need to do.

[Flatbed136]

Well, I think I finally got it.

I have not tried them out while the truck is running as I'm waiting for a new voltage regulator.

I have a few more pictures and will try to give some information on how I went about doing it so I can hopefully give back and help someone like all of you have helped me.

First thing I did was unbolt the master cylinder from the firewall. It would be easier to tie up the master to the hood or something to get it out of the way and give you room to work as others have stated but I did not do this. I can see the reasoning behind it as the master will want to go back to its original position. Take your time and be gentle with the lines and they will move where you need them too with out any kinks or bends.

I didn't disconnect the lines from the master. This has been talked about quite a bit in other posts. Saves yourself another step.

Place the pedel linkage through the firewall and put the booster in place over the four studs in the firewall. There was one bolt in the lower right hand side with a washer on it that you have to take out to get the booster flush and than put it back in and tighten down.

Connect the booster to a vacuum source. I connected mine to the manifold. You can see where in the picture below.

After talking to cparman, I finally think I figured out how to check the clearance between the master and the booster. My push rod was not adjustable.

I used rope caulk. I placed a 1/4" ball like cparman talks about in his posts right below the hole in the master and between the lip going around the outside of the master. Press it in place so it sticks and won't move around on you when you put everything back in place. Bolt the master back up to the booster nice and tight. Don't push on the brake pedel. I waited a few minutes before I took it back apart again. Unbolt the master from the booster and look to see if the caulk was squished. As cparman has stated, your looking for a 1/16-1/8" indentation in the caulk. Below is a picture of where I put the putty and also what my squish looked like when I got done.

I only had one hole in the brake pedel arm so I had to drill a new hole. Others have stated the top hole is for the manual setup and the bottom is for the power brakes. I went 1" down from the bottom edge of the exsisting hole and about 3/4" from each side to find the center. If you do this with the pedel installed in the truck like I did, you will have to tie back the brake pedel just enough so your bit passes by the clutch linkage and other obstacles. It was trial and error a few times before I got everything where the bit wouldn't rub againest anything.

The bolt that goes through the pedel and linkage is tricky to get in the lower hole and even the top hole for that matter. I removed the plate with the pedel bumpers on it and also the brace that holds the steering colum in place under the dash. I ended up going under the hood and loosened the bolt and nut on another clamp around the steering to get me some more play. It would be easier if you had a helper but it can be done by yourself as I did it.

I went with the advice posted above and and have about 9/16" of threads showing on the linkage going to the brake pedel arm. As stated this is for the pedel height only. Below you can see where the pedel sits now with the new hole drilled etc.

You will have to adjust the stop light switch. I have not done this yet but your brake lights will stay on if you don't. I also had to fish the stop light wire attaching to the proportioning valve out of the cluster of wires to make it longer to reach.

Check your pedel free play. There is quite a bit of information on this posted in threads and from what I've gathered, the amount may be different depending on which way you measure it. Someone hopefully will chime in and correct me if I'm wrong.

I don't have to push the pedel down very far before I feel resistance and the pedel feels nice and stiff when you do depress it. Using the top hole before, I never felt much resistance.

One thing to check is to make sure your using a master for the power brakes. I ran across a thread about that. I can't remember if the truck had power brakes on it when I sold it or not. When I bought it back, it just had manual and that is the master I'm using. Something I may have to look into if something isn't quite right.

Hopefully if I missed anything, others will correct me or post some additional information. There is plenty of information posted on how to do this but I found using different search words brings up information about it not listed in other searches etc. so I'm hoping this post can provide most of the information needed to complete the job.

Thanks again to everyone that has helped me and I'm sure if something isn't right when I do test them out again, I'll be asking for more help.

I still have to get a few washers and button up some other things before its ready to go but I think I'm 99% complete.