Hi. Barnsydog, United Kingdom. I have a 502 BB Chevy that was fitted with a 871 Blower in a Glass 34 3 Window. Too quick for the street, so I removed the Blower setup. I fitted a Torker type Manifold (new) and a 780 cfm Quick Fuel Street/Strip Vacuum Secondary Spread-bore carb. The vacuum secondary won't open. I've changed diaphragm. I'm told the Silver spring may be too strong. Any ideas? It's running very rough idle slightly better when warm. The Cam is Isky lift .340" .358" can anyone help?