When I rev the engine in my car with the transmission in park the secondaries do not open. Why is this?
The secondaries on a Holley carburetor will not open because the engine needs to be under a load. If you are uncertain if they are opening or not, clip a paper clip on the secondary diaphragm rod. Push it up against the bottom of the secondary diaphragm housing. Now drive the vehicle. When you return, look at the position of the paper clip on the rod. If it is lower on the rod you can tell if the secondaries opened and how far. This is also useful in determining if you need a heavier or lighter secondary spring.