Power Brake Conv, Push Rod Question

[Rakort]

Ok, I have about finished my PB conversion on my 68 C10 and of course I'm having push rod issues. Seems to be a common problem, but I couldn't find the answer in the archives by searching so here goes.

I got a complete PB assembly including pushrod off of a donor truck. I believe it was a GMC 4x4 1/2 ton maybe a 70 or so.

I've installed the assembly on my truck (see picture) and hooked up the push rod to the brake pedal. The issue I'm having is adjusting the push rod. When I adjust the push rod longer to allow the pedal to come all the way up and contact the rubber stop there isn't enough thread engagement between the rod and the adjustable rod end. When I have reasonable thread engagement (maybe 3/8" or so) the pedal gets held off the rubber stop by maybe 1/4" to 1/2".

How is everyone dealing with this issue? Accept the fact that the pedal doesn't come all the way back up and hit the rubber stop? Fabricate a longer rod? Run the rod with dangeriously few threads engaged?


Seems like the person in the following thread had a similar problem, but doesn't mention how it was resolved.

Thread covering similar issue





Thanks
Brian

[SWEET7T]

Don't worry. Mine doesn't hit the rubber bumpstop either. I did the conversion on my '70 2 weeks ago. I just used it as a good excuse to have my brake pedal closer to being even with my gas pedal, so that it is easier to get my foot on the brake pedal. I hated how high it was before power brakes. My pedal doesn't move much at all, so I'm not worried about hitting the floor.

[Rakort]

Thanks, that is a little reassuring. I have a terrible problem with being over anal about such things......I like to make everything just so...

Looks like this guy also had a similar issue....

http://67-72chevytrucks.com/vboard/s...threadid=67547

[Suicide-D]

What side of the pedal did you mount the rod? on the left side or right side if you are looking straight at the pedal? I had similar troubles and found that I had it mounted on the wrong side. I have about 4 turns worth of threads engaged then the jamb nut tight. I have mine mounted on the left side. I had to drop the column to get the bolt in . Let me know if you need more info.

[Rakort]

4 TURNS!! Wow, I'd be a little more than nervous with that arrangement. If that pops apart you'll of course have no one home in the brake department!

I have the rod mounted on the left side. I noted that when I took the old one out. Yes it was quite a hassle putting the bolt in. I finally took a pin out of the booster linkage on the booster bracket to allow the rod to move freely than I was able to get the bolt in without dropping the column.


Anyone else have similar experiences with this??

[lolife99]

The only conversion I have done was on a '69 burb with '75 parts, including the power booster. I found out the rod wasn't long enough when I tried to bleed the brakes. I took the rod to a weld shop and had it cut into and lengthened about an inch or inch and a half. I can't remember. Brakes bled fine after that. (I wasn't depressing the master cylinder all the way.)I hope this helps.

[lolife99]

make sure the rod is in the correct hole on the brake pedal arm, for the application. Upper hole for manual brakes, and the lower hole for power brakes.

[Suicide-D]

what is it with the mutiple holes??? I have 3 trucks and all have 1 hole in the pedal arm. I was told that in my post so i checked...2 are power brake trucks and of course the one that was manual...What gives... do I have mutant trucks in this department also?

[Suicide-D]

if 4 turns makes you nervous you could do like suggested and get it lengthened... or tack weld the jamb nut to the head part...

[lolife99]

I think the one I did had, had an upper hole and a lower post?!? I can't remember. Maybe someone can post a pic. All I know is that on manual brake trucks, the rod is positioned higher on the brake pedal so you have more leverage with the "harder to push" manual brakes. Power brakes require less foot effort, so the rod is mounted lower. If I remember right, I put the master cylinder on and tried to, line up the rod in a staight shot to the pedal. Seems like there was a hole,... or a stud that I removed or drilled out. Sorry for the lack of memory. It's been about 12 years since I did this.

[Rakort]

Well I've read a couple of times also about the two hole thing in the pedal arm, but I'm positive my arm only has one hole and no other studs/posts for the push rod....what was mentioned about the leverage issue makes perfect sense though.

After going through my parts box this evening I ran across a longer push rod end that matched the OEM one except it was 1/2 to 3/4 inch longer. I was aware of the pushrod issue back 2-3 years ago when I snagged the booster off of the donor truck so apparently I went around the yard at that time and found a longer push rod end and snagged that also. I installed that, got it adjusted out and now I have about 1/4" free pedal and the pedal comes all the way back to the rubber stop AND I have about 1/2 to 3/4 inch engagement on the threads. I guess I had the solution to my problem right under my nose by didn't even remember obtaining it!!

I just started bleeding things out, but haven't had much luck yet. My boy's leg got tired out before I got any fluid out to the wheel cylinders! Seems like it was SLOW going......I basically had the system totally drained. Is there a particular corner of the vehicle I should start bleeding first?

I should be able to bleed the power brakes just fine with the engine off, correct?

Brian