redwingvette

No, put a vacuum gauge in the line and see what is happening. Does it feel lik the power brake booster is working? The thing may be leaking.

MasterDave

Remove this line, plug the carb outlet and start it up. Adjust your idle. Plug the hose back into your brake booster. If it idles way up you've got a leak in the booster or the line. Check your connections at the rubber hose, the hose hardens here, you may just need a new hose.

MoMo

I agree. I think you may have a leak in your power brake booster, and perhaps you've adjusted the carb around it, so that when you close off the vacuum leak, your idle goes way down. Another thing you can do is if you have a vacuum tester, pump some vacuum into the power brake booster and see if it's leaking. Most of us, however, don't have a vacuum tester (not a bad thing to buy when you own a C3!!!). So in that case follow the last advice, that will tell you too.

427V8

Me too, ther should be no air flow through the power brake vac line except when you apply the brakes...
Plug it and THAT is how the car should be setup.

QuickVet

what does it mean if when you step on the brakes and the idle drops to the point almost stalling? is that normal?