I was wondering how you tell if the vacuum secondaries of a carb are opening. Does there have to be an engine load? This weekend i tired to see if mine would open, i have the lightest spring in my quick change holley carb setup. And they would't open when i park, even revving to 4500 rpm.

 

You gotta be under load. Free revving won't do it.

 

I used to think that too, I mean, every V8 I've had was like that. But the air valve on my Oldsmobile will open revving it in park.

Maybe only small engines do that