"How much?" is the maximum amount of mechanical advance the mechanism delivers. Performance engines like a certain amount of advance through most of the upper operating range, usually referred to by tuners as the amount of "total" advance. Typically, Mopar engines respond best with between 35 and 40 degrees of total advance, depending on the combination. The "total" advance is the sum of where the timing starts, the initial timing setting at idle, plus the amount the mechanical advance mechanism adds in. Stock engines don't need a lot of initial advance to provide smooth idle and good off-idle acceleration without detonation, and typically run initial timing near TDC (top dead center). By contrast, a hot-cammed street sweeper often needs 15 degrees or more just to idle cleanly. If both engines run best with 35 degrees "total," the stocker, starting at 5 degrees initial, will need way more mechanical advance in the distributor mechanism to get to 35 degrees "total" than would a hot mill idling with 15 degrees initial (10 degrees more, to be exact). Setting up the amount of mechanical advance comes down to figuring out what the desired (or required) initial timing setting needs to be, then limiting the mechanical advance to the value required to achieve the optimal total setting.

The second part of the mechanical advance mechanism to consider is the rate at which the advance comes in. This is the function of the advance springs. Stiffer springs bring the advance in more slowly, while lighter ones let the advance come in sooner. The springs answer the question of "when?"

There are many theories on what is best, but often the mistake is to go too quick with the advance rate. Some springs are so light that the mechanical advance will start to swing in at idle rpm, which can cause real driveability problems, erratic idle, or the engine nosing over and stalling when the rpm drops and the engine suddenly loses a fistful of timing at idle. Detonation can also result from too much timing too fast. Considering that in a performance application the engine flashes against the converter over 2,500 rpm, or much higher in a racier car, a super-quick advance curve gains little, if anything. On the other hand, the factory setup feeds in additional timing rather slowly in the high-rpm range-well beyond the point where the "total" should be. What is best for your car depends upon the combination, although a rule of thumb is to have the advance start a few hundred rpm over idle speed and reach full advance by 2,500 rpm or so in a typical street car-higher if it detonates. The curve is easy to map with a timing light and tach.

While the distributor handles the switching and routing chores, it has little to do with the spark energy. This is the primary function of the control unit and ignition coil combination. The control unit affects the amount of primary energy and saturation time to the coil, which influences its output. There are a variety of Mopar Performance ignition-control units available for specific levels of performance and rpm. Ultimately, it is the coil's job to generate the voltage that goes to the spark plugs. A high-performance ignition coil is worth considering in a performance ignition, particularly as demands of rpm and compression go up. Be aware that some race coils are not suitable for prolonged low-rpm street use.

Our recently acquired '68 Barracuda's 318 was sparked by a stock points ignition. Suffice to say that it was one of the first items on the hit list in upgrading this machine. We had stacks of the stock production distributors on hand, and decided to dissect one for a full performance rebuild. Eventually, we plan on beefing up this 318 with a set of ported iron heads, and a big cam and induction combo, so the advance was modified accordingly. Even in a stock-for-stock exchange, electronic ignition offers the kind of reliable, long-term performance that a points ignition can never match.