[Charlie Brengun]

I've got a 472 caddy with a quadrajet. Once I hook up the brake booster to the vacuum port on the Quadrajet and rev the engine when the secondaries open they remain open, they keep sticking open until I close them manually.

so far:
I've replaced the intake manifold to carb gasket, same issue
I've tried a different quadrajet, have the same issue.
I've unplugged the brake booster and plugged the vacuum port on the carb, issue goes away (for both carbs).

The vacuum booster for the brakes is new but the car has sat for a year after installing it.
I'm looking for options here, I'm overseas and don't really want to replace the vacuum booster only to conclude the issue doesn't go away. So what else could I be looking at?


Funny thing is the Qjet I rebuild with a Cliff's kit and use of his book runs better than the other ebay rebuild Qjet I used for testing..

thanks,

[camerjeff]

Just a thought, but does your car have the check valve installed on the brake booster? It is usually the roundish plastic connector that attaches the vacuum hose to the booster, but I have seen some inline check valves installed in some aplications. Just thinking out load here, as I have never heard of that issue before.

It would look something Like these

http://www.autopartswarehouse.com/sk...n+%26+Steering

http://www.jcwhitney.com/ac-delco-br...FbEBQAod103BpA

If bad or not installed it could be letting vacuum from the booster backfeed into the Carb?