TR,
Vettepilot makes a good point, and if you can learn from someone, then that definetely is better. Nevertheless, it is like you said -"...how will I ever learn"?
Therefore, I am going to give you some theory on the use of a timing light. This will help you understand the process better when you finally get around to take the car to the mechanic.
One can find a timing light for sale in most Auto parts stores. They cost between $50 and $200 dollars depending on the number and type of functions it performs. There are self-powered timing lights and timing lights that require power from the battery. One drawback that I have noticed on the timing light that requires power form the battery is that the power cables are just a bit short for use on the Corvette, for the battery is located behind the driver's seat, and it just won't reach all the way to the engine dampener, so that one can easily aim the timing light gun properly.
A semi-average timing light will include the following functions; timing light on/off switch or selection, dwell function to allow for timing of different number of cylinder engines, rpm function, and adjustable advance, so that one can determine the number of degrees before top dead center (BTDC) the ignition of the fuel / air mixture is taking place.
The timing light positive lead (usually color-coded red) is connected to the positive battery post. The negative lead (usually color-coded black) is connected to the negative battery post or a good ground source. One can connect the black lead to the battery post; however, it is safer to a good ground source away from the battery, for battery fumes are considered flamable, and a spark could ignite the fumes.
There is also a timing pick-up sensor that is shaped like a clamp or loop. This is connected to the #1 cylinder ignition lead. One simply press the clamp open and set the ignition lead to rest inside the loop or clamp. Care should be taken to avoid contact of this sensor with the hot parts fo the engine, and it should be as close as possible to the #1 cylinder spark plug end of the ignition lead.
Some timing lights also include another lead (color-coded green) that can be hooked to an rpm gauge. This will help in not having to switch between the rpm and advance functions on the timing gun, but it is not absolutely necessary.
The engine dampener has a mark across it that runs from front to rear on the outter circumference of the dampener wheel. This mark is designed so that when it is installed onto the engine it is synchronized with the # 1 cylinder piston (the left-front most positon on the GM engine). The ignition lead for this cylinder is connected to the distributor (which controls the firing order of all the cylinders). When the #1 cylinder piston is in its way on the compression stroke, the igniton is schedulled to ignite the fuel / air mixture X number of degrees before the piston reaches top dead center. This is your advanced timing.
The advance function on the timing gun is very handy, for one can place the engine on idle, aim the light gun at the dampener (where the timing mark is found), adjust the advance up on the light control panel, and maintain the "visible" timing mark aligned with the zero degrees on the index plate.
For example, lets say that the engine is idling at its (on the example) idle speed of 800 rpm, and the timing light when flashed does not seem to be even close to the timing scale plate next to the dampener, then one can "advance" or scroll the number of degrees up until the mark alings itself with the "0" degrees mark on the timing scale plate. This would be your basic timing advance setting. Hi performance engines benefit with 12 to no more than 14 degrees of basic advance at idle. Stock engines use the manufacturers recommended setting.
So in our example above, if one would want to change the basic timing to a lower or higher value, then one would have to loosen the bolt that holds the distributor from rotating, and turn the body of the distributor clockwise or counter-clockwise respectively to affect a change in the number of degrees that the ignition of the fuel / air mixture would be set to take place.
Basic advance timing should be done with the vaccum line from the carburator plugged. After finding the ideal basic advance setting don't forget to tighten the distributor bolt.
To read the total mechanical advance one would have to accelerate the engine speed to predermined speed settings (if stock) or aproximately 1500, 2000, 2500, and 3000 rpms if you have a modified engine. Your total mechanical advance should be reached between 3100 - 3200 rpm or as described by your stock engine manual. While one accelerates the engine, the dialing of the advance on the timing light would need to take place in order to align the timing mark at the zero mark on the timing plate. Little by little one would get to 3,000 rpm (about 500 rpm increments works well). In our example above, lets pretend that the most mechanical timing one can get is 28 degrees BTDC. Now, we need to dial the vaccum advance.
One would connect the vaccum line and read the advance timing at each of the rpm settings above or as described by the stock engine manual. If at 3000 rpm one reads 33 degrees BTDC (28 mechanical plus 5 vaccum), then we could adjust the vaccum canister clockwise to gain an additional 5 degrees or reach the total advance recommended for your stock engine. Even Hi performance engines (street) should not be dialed with more than 38 degrees BTDC. It is good that the engine be taken to 3250 rpm to ensure that no additional vaccum advance is taking place. If by chance the timing light stops flashing at the higher rpms, then dial-back the vaccum advance. This will clue you in that it is dialing too much timing. The timing light cannot keep up and quits trying.
wheeeewww...this one finger typing is cramping my hand...:L
This is a glimpse at how timing is done. Maybe someone can chime-in any corrections or clarifications to this for your benefit, but I think that I explained it pretty well. Now when you go to the mechanic you'll understand the timing process a little better while he works on your fine Corvette....
