Brake pedal issue after conversion to power assist from manual on 1969

[Kw69]

Guys need your help. To explain it best, I bought a new conversion kit from eBay to convert manual to power assist. I hooked it all up today and ran the power booster hose to the back of the carb. I added the nipple for that. The issue now is that I have about one inch of pedal travel, and the brakes grab so hard it will throw u into the dash if you did not have a seat belt on. I called the guy who I purchased that kit from and he showed me how to adjust the booster which I did to the most, brakes are slightly less grabby now but the pedal is still tight and only moves about an inch and it really grabs. Ok so..... Why? Is this normal? I mean the brakes are really touchy. And the set up has a 8.5 booster dual he said that is the best and a heavy duty unit. I don't really know since first for me. Anyway thoughts? Btw also bleed the system like crazy and also bench bleed the master.
Thanks!
Kris

[Steeveedee]

Master and wheel cylinders are different size bores between manual and power brakes. Since you already have the power brake master cylinder, you can change out the manual wheel cylinders for power brake ones. The hardware (springs, etc.), should still be the same.

[geezer#99]

I bet you didn't change your pedal ratio!
Manual is 6 to 1.
Power needs to be 4.5 to 1.
You need to drill a hole in the brake pedal arm lower. Likely about 1 1/2 inches. Measure yours first to be sure.

[Kw69]

Wow did not know about either of those....I did not know about the pedal ratio.... Or the cylinders. So drop the pedal hole down 1-1/2 inch and reinstall, makes sense to me....at 43 and still learning !!! Thanks guys so far

[Kw69]

So after drilling a hole and reinstalling, wouldn't the pedal be further in? This am when setting the arm to the brake, I had to adjust it way out... I don't think that I have a lot of adjustment left but will check again.

[LockDoc]

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I have changed 3 trucks over from manual to power brakes and never had to change wheel cylinders or re-drill a pedal arm. I have always used stock boosters so there could be a difference in the 8.5 inch dual booster. I have also always used the port in the rear of the intake manifold instead of the back of the carb. On my White '67 SWB I even used the manual master cylinder with no problems. I didn't even unhook the lines when I installed the booster, just unbolted it from the firewall, pulled it back, and bolted it to the booster after it was installed. I know I changed the master cyl to booster rod.

LockDoc

[70STOVEBOLT]

Originally Posted by LockDoc

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I have changed 3 trucks over from manual to power brakes and never had to change wheel cylinders or re-drill a pedal arm. I have always used stock boosters so there could be a difference in the 8.5 inch dual booster. I have also always used the port in the rear of the intake manifold instead of the back of the carb. On my White '67 SWB I even used the manual master cylinder with no problems. I didn't even unhook the lines when I installed the booster, just unbolted it from the firewall, pulled it back, and bolted it to the booster after it was installed. I know I changed the master cyl to booster rod.

LockDoc

X2, I installed the 11" booster. The only thing I did not reuse was the master cylinder pushrod, I used the adjustable one that came with the used booster that I bought. If your brake shoes were fairly new and the rest of the system was in good shape, it would be normal to only have a small amount of travel. The last time I replaced the brake shoes and adjusted them I only had about an inch of travel.

[LongBox]

Always want to support guys who are working to upgrade the safety of their older vehicles, and better brakes are always a good idea. But, having said that, I really do not find anything particularly wrong with the manual brakes on my 69 for everyday driving. I think that if I was using the vehicle for hauling heavy loads, or driving in the mountains, I'd want to change to disk brakes up front to get more stopping power and better fade resistance. But the manual brakes, with drums at least, do not seem to need a lot of effort on the pedal, and they will bring the truck to a pretty fast stop.

For the OP, it sounds like there is an issue with the booster itself, not that it doesn't work, but that it might not be the appropriate unit for the truck. Sounds like it gives too much boost. Sort of like the power brakes in a mid 50s Caddy.

[Kw69]

Wow thanks guys, yep I also began to wonder about the booster. I called the vendor back and he said it was a heavy duty unit and he thinks that's why it so quick to stop. I did drive it around today and began to learn the new method in using the brakes. I like the drum set up and will keep that. I just upgraded to a booster setup cause the old master cylinder finally gave up after 47 years... Lol anyway enjoying it back out on the road. Going to take it up Friday to a really small gathering car show close to my house. I'm working on installing the ac system in the truck when I'm able. Been a really fun adventure and just really have enjoyed owning such a cool piece of history.

[geezer#99]

Did you try drilling a lower hole?
Might make them less touchy.

[Kw69]

No sir I did not get the time to do that today. I have been working on several home projects and of course my job. I won't be able to mess with it till next week. Drove it around today and picked up a bunch of supplies and wood for my upcoming home project. Stopping is touchy but getting more used to it. I love the 8 foot bed, my 09 is an HD truck but only 6.5'bed and some of that is covered by a tool box and 5th wheel rails. So easy to drive the 69 for any lumber supplies. Truck still working 47 years now, can't beat that. I am sure that you guys always get people checking out your truck as well. It seems to be quite the attention getter.. Even more then my buddies vette...lol

[LongBox]

Yep, the long box is great for lots of things. Both my trucks have the 8 foot box.

And yes, these old trucks get lots of positive attention when you take them out. Bikers, heavy duty truck drivers, and even ordinary guys will give you the thumbs up Enjoy it!!