Wrong distributor for 69 318?

with the engine at idle and the vacuum advanced plugged in, what is your timing. if its not 13 then your vacuum advance is pulling at idle. Then unplug the vacuum advance and what is your timing. if 13 there is your answer. Simply put your vacuum advance is coming on too soon. You can adjust those oreily vacuum pods on the distributors, i have several of those my self. you want the know what you vacuum is at cruise assuming 3,000 is your cruise rpm. That is when you want the vacuum advance to kick on . Also doubled check the gap between the reductor and the pick up in the distributor make sure its at spec.