I've recently bought a Chrysler 408 stroker engine from BluePrint and I'm trying to get my stock 3x2 carb setup, from a '70 AAR Cuda to properly work on it. The secondaries are staying open once the engine gets revved and it won't hold a healthy idle. We swapped out the diaphragm springs to the black ones as we saw on a different forum to do. Any other suggestions?