okay, here goes. have a stock chevy 350 with a brand new edelbrock 600 cfm with electric choke. start the engine, it idle real high.I haven't even touched the idle speed screw yet. I turn the distributor counter- clockwise to bring it to the chevy timing specs and it races up more. i covered the carb with my hand and the engine almost shuts off, so wouldn't this mean there is no vacuum leak. Also wondering if the timing chain has stretched?, etc. Thanks for any info.