one other question when you say pull it bact 1/2 to1 inch i assume you mean retard the timing?

 

As far as fuel goes, even if your pulling engine doesn't need it for octane reasons - find a good, high quality racing fuel.  For no other reason than consistency.  I don't pull anymore, but this fuel problem is driving me nuts with my gas-burning farm tractors, antique cars, and carbureted motorcycles.

 

A vacuum guage is great for tuning, particularly lean-best-idle and timing.  What it does for your timing is compensate for altitude and atmospheric pressure.  If you adjust your timing until maximum vacuum is reached, this is the best timing at idle for your altitude and weather conditions.  The generic backing off 1/2 to 1" mmHg is to compensate for crappy fuel and crappy advance curves.

 

Theoreticly, if your distributor is curved properly to your engine and fuel - the vacuum gauge is the quickest and best timing tool you have, simply adjust to max vacuum.  Even if your distributor is not curved so good, you can adjust your timing to get max power at whatever rpm you are running at max power, then back the engine down to idle and observe what your vacuum is - bingo - that's your vacuum setting at idle.

 

Lean-best-idle is simple as well.  Adjust your timing to max vacuum first (regardless of whatever your final desired mmHg is), then adjust the idle mixture screw lean until you notice a drop in vacuum.  Go rich until it reaches max again, then adjust your idle speed down.  Repeat.  You are looking for the highest vacuum reading you can get, as lean as your mixture screw will allow, at the lowest idle speed your engine can maintain.  Once this is done, return your idle speed to whatever you want and return your timing to whatever mmHg you want to run.

 

About the only time I use a timing light anymore, is to correlate vacuum readings to actual distributor timing or on a "first fire-up" after having the distributor out.