Brake Booster and Idle Question

[dave2953]

I recently installed a booster/m.c. out of a 79 Scottsdale. I changed the idle to 1000 (in park) because the truck shook at idle after the install. I figured maybe the booster diaphragm was leaking, but when you disconnect the vacuum line to the booster and plug it, the idle doesn't clear up. Today I set the idle back to 800 and now the brake pedal drags. You have to lift the pedal to get the truck to roll. What is causing this? I tried spraying WD40 on all my vacuum lines to check for leaks, but didn't notice a change in idle speed. Sorry for the long post and thanks in advance for your help.

Also, the booster runs to a "T" fitting in the manifold. The other side of that "T" is for my modulator, and my PCV runs off the base of the carb.

[Longhorn Man]

your mod doesn't use enough vac to worry about.
If the brakes are dragging, then there is a mechanical problem, not a vac issue.
Double check all of the connections...the pivit points for the pedal, rod, and linkages, look for one that is too tight, or binding.

[dave2953]

Originally I had the the nut that connects the rod to the pedal too tight and that was keeping the pedal from returning. I loosened it and that solved that problem. It wasn't until I changed the idle this morning that the pedal stopped returning to it's rest position. The truck has run rough at a "normal" idle setting ever since I've added this setup and I thought it was due to a booster problem. Sorry if I'm not making any sense

[PICKMUP]

Go get a 67-72 booster setup and quit trying to make something else work! It is just too easy to get the "right" parts and eliminate all the potential problems that go with mixed systems.

[dave2953]

Ultimately I think that's what I'll have to do. I have a 79 donor truck and tried to make it all work, but I had to modify so many things to get it all to fit. I just figured since the parts were there I would try and put them to good use.