I've got a 68 coupe with a 289. It's got a Edelbrock 4 barrel, and a Pertronix ignition. I've been trying to set the timing in it using a vacuum gauge. I can get the timing correct when it is at a fast idle, but when the engine slows itself down a minute later the timing falls off and the engine dies within 30 seconds. I've tried adjusting the timing when the engine slows down but when I turn the distributor I don't get a readable response right up to the point where the pressure completely drops and the engine dies. Can anyone help me?