Booster Replacement 70 C10

[lutronjim]

My vac booster is sometimes hanging brakes on at about 25%. This happens after a pretty quick stop (not panic). Most times I can clear by a quick stamp on the brakes. It wouldn't release the other day and I pulled vac hose and it released.

The booster will not hold vac after engine shut down. It is an 11" single unit.

I would like to have a little more boost and was thinking about going to a dual unit. My fear is that I might get too much boost. Wondering if a proper functioning 11" would be enough?

Any help would be appreciated.

[lutronjim]

Forgot to mention truck has disk on front.

[68Gold/white]

Converted disc.......or factory disc???

I'm not sure there is a solution to better braking on a pickup by altering the vacuum. Now...if you have a lumpy cam and engine is not making enough vacuum for the booster, you definitely could have a problem.

In my opinion, a booster, be it a single or double, unit, manufactured to do the job for your pickup should be all you need.

I've never heard of a booster causing brakes to stick......I am not the know it all, either...

If you have a 70 with factory disc brakes...nobody here is going to believe you...LOL I have started a couple of threads about 70's with factory disc brakes.....nobody has seen such a pickup....I think I had a customer with one, that got shot down by theories...that might be true....

[68gmsee]

The truck came with non disc brake shoes so it's been converted. About all you can do is to swap out the booster. With disc brakes you shouldn't have trouble with a double booster. I had one on my 69 with shoes all around and it was super touchy.

[lutronjim]

Thanks

I put the disk on front. The engine is an LC9 - a 'connect and cruise' package.

The brakes were hung maybe 25% - all I know is that when I pulled the vac hose they released.

[68gmsee]

One more thing to look at is the brake push rod. Make sure it releases when pedal is allowed to go back up. Just a small amount of tension may keep the booster from releasing pressure.

From CPP site:

"Check freeplay in the pedal by applying pressure to the pedal with your hand and noting how far the pedal travels before resistance is felt. It should be approximately 1/4". This freeplay allows the master cylinder piston to return to the "at-rest" position and prevents preloading the system. Too much freeplay will drop the pedal too far before applying brake pressure and may even hit the floor before applying full braking force to the system. Note freeplay is also dependent upon proper adjustment of the booster pushrod.