Timing is Everything:

Distributor Tuning for Power and Economy (Part 1)

The test mules, a 1967 Dodge Dart with a 225 slant six (bronze, foreground) and a 1975 Dodge Dart equipped with a 225 slant six (gold, background). A Pennsylvania College of Technology graduate (class of 1969) donated the ’67 Dart and the ’75 Dart is from the author’s personal collection.

When it comes to the internal combustion engine, there is no mistaking that timing is everything. Providing a properly timed ignition spark in combination with a perfect air/fuel ratio in a cylinder as the piston moves toward top dead center will result in the best torque output of the engine. With the best torque output, the engine will be more efficient within the cruising RPM range, and this, in turn, has an outcome of better drivability and fuel economy. If there is any disruption of the introduction of the spark, an incorrect air/fuel ratio, or a loss in compression, the power and economy will suffer leaving the driver less than satisfied due to a sluggish operation of the vehicle and the high costs of operation caused by the poor fuel economy. Modern computer controlled engine management systems control all the ignition timing and fuel trim management to ensure close to perfect operation at all times. While the modern vehicles maintain a razor sharp tune in most conditions, how could the old Mopars be tuned for the optimum tune while using the rather rudimentary mechanical and vacuum controlled ignition parts and a carburetor of years gone by? To investigate what could be done to improve the power and economy of older vehicles, two Darts were selected for an extensive series of ignition tests. One Dart was the Pennsylvania College of Technology’s (Penn College) ‘67 with a 225 slant six. The other Dart was a ‘75, also sporting a 225 slant six. To handle the economy part of the testing, just the ’75 Dart was selected because it was the only licensed and registered vehicle of the two. The power and economy testing would only incorporate the distributor modifications for this article.