At what rpm does the vacuum pop up to 11/12?
My Dart booster requires about that to begin charging. It charges in a few seconds. Even on a long slow stop from whatever speed, that booster worked right down to near-stopped, at which time, it doesn't take much effort to brake as a manual.
Here's your test.
Shut off the pump.
Hook up your booster to the intake plenum; NOT an individual runner.
Make sure your vacuum checkvalve is working, get one that provides a vacuum tap on the booster side of the valve. Hook a vacuum gauge to the booster, that you can read from the cabin.
Pump your pedal a few times to empty the vacuum chamber.
Put some modest pressure on the pedal, and just maintain it, then start the engine.
When the booster comes on line, the pedal will began to fall under your foot.
Note the vacuum at which this begins.
If the pedal does not fall, rev the engine up to 10 inches vacuum, then 11 then 12 or until the pedal falls. That is your minimum vacuum for that booster.
>If the pedal does not fall, something is wrong. Either the booster is defective, or has an extremely high minimum vacuum requirement, or more likely, the pushrod length is too short.
But if it works right,
go for a drive and make note of how often and under what circumstances, your vacuum falls below the minimum.
If your check valve is working, the booster will continue to work, even if the engine stalls, for at least one long slow braketest.
Finally, put her in park, then charge yours up to whatever maximum vacuum your engine can achieve, then shut the engine off,. Do not touch the brake pedal. The booster should maintain the vacuum above the minimum, for several minutes.
>If it doesn't, something is wrong. It could be a faulty checkvalve, a faulty control valve, or a pedal not parking properly, which could point to a too-short pushrod.
Happy Hunting.