No worries man, the only silly question is the one not asked, if you donÆt know the answer. Vacuum and mechanical advance are 2 different, independent systems that both affect the over all timing. Vacuum advance will come into play when you have high vacuum, and is there to advance the timing when there is a low load on the engine (ie highway cruise) to improve fuel economy. Mechanical advance comes into play constantly while the engine is running to adjust the timing based on engine speed. At idle there should be no mechanical advance, and as the engine speed increases the counter weights pull out and the timing is advanced. This is to allow for proper flame propagation across the cylinder. If it advances too far you will hear a ping because your engine is now trying to compress an explosion. If it is not advanced enough then you donÆt take full advantage of the combustion because the piston will already be on its way back down before the explosion reaches its way across the combustion chamber. The mechanical advance does its best to compensate for the flame propagation time at different engine speeds. So really you have 4 things that will come into play when setting your timing. The initial distributor set position, the mechanical advance, the vacuum advance, and any play from worn parts.

If you pull your distributor cap off and look down inside the distributor you should see some counter weights and springs on a plate, this should be just below the pick up for the electronic ignition, all of these parts should move if you grab onto the rotor and give it a little twist (say 20-30 degrees or so). The vacuum advance will attach to the plate the pick up for the electronic ignition sits on, and will move if you suck on the vacuum advance hose.

Man getting on this site at work sucks, I started this at 9:00 am and I am just getting back to it to finish it at 4:50 pm. Go figure.

Sean