[Clarke]

First of all, this is not my area of expertise, so I appreciate your feedback. Given the subject of this thread, I'd like to explain how I arrived at 16 degrees (in lieu of the factory spec of 7.5 degrees).

Typically, I follow specs closely, but there was a previous thread where someone was talking about advancing the timing, which I've heard so many times over the years, but never much detail on how much advance.

Many old timers I've spoken to over the years say they never use a timing light; they adjust the distributor (advancing the timing) until the motor starts to run rough (detonation), then back it off a little. (What's a little? I don't know? LOL!) I tried that with my 305 and it started running rough at 20 degrees, so I backed if off 4 degrees.

Correct me if I'm wrong, the engine achieves the greatest amount of power when the combustion process happens when the piston is at it's highest position (least amount of open area), just as the piston is starting on it's "down stroke". This is why when you advance the timing from factory spec, the engine idle increases. As you are reducing the amount of open area during the combustion process, the increased energy pushes the piston down, resulting in more power.

In the previous thread I mentioned above, I noted I completed several dozen timed runs, which consisted of cruising in 4th gear (I think 40 mph), then flooring the gas pedal and holding it until I hit 70 mph. I experimented with 7.5, 10 and 16 degrees. The times between 7.5 and 10 degrees timing were very consistent, but with 16 degrees timing the times were consistently faster. I duplicated the timed runs the following day with all three timing settings in reverse order and the results were very close to the day before.

Again, I appreciate the feedback. I obviously do not want to cause engine damage if the above justification is not correct.