Back firing through the Carb! But I think the advance is screwy! I have full vacuum at the distributor at idle, which means I have full advance at idle... correct? I have checked the vacuum routing and all is accurate. But there must be a check valve or temp check valve that's not working. I don't know how to check the valves. One of them is located right in line with the advance and when I try to pull a vacuum on it, it is open in both directions... meaning I can't pull a vacuum either direction. Isn't that check valve a delay? How is it supposed to work and how do I check it? Thank you for your help
Steve