In a previous issue we searched for "TDC" on a rusted harmonic balancer on our Packard 356 straight 8.  With the balancer newly painted and stamped with "TDC" and timing degrees, we were ready to put all components back on the stripped block.  In this issue, we will set the timing and check a vacuum advance.  

        We are keeping the original Autolite 6-volt positive ground "single point/condenser system".  The ignition system consists of:  battery, ammeter, ignition switch, distributor, ignition coil, spark plugs and wiring.  Its purpose is to supply sparks across the spark plugs, igniting the combustible mixture in the cylinders.  The system is made up of two circuits:  1. Primary (low voltage) and 2. Secondary (high voltage).  The primary circuit's low voltage is changed to high voltage in the secondary circuit by the ignition coil.  6-volt systems supply a full 6 volts to the coil.  The coil then steps the 6 volts up to a higher voltage required to make the current jump the spark plug gap (on our system 18,000-20,000 volts at the spark plugs).  The path of the current flow with the engine stopped and ignition switch on in the primary circuit, is battery to starter switch terminal, to ammeter, to ignition switch, to primary winding in the coil, to insulated breaker point, to grounded breaker point that is attached to the metal distributor casing where the current flows through the engine, to the engine-to-frame ground strap, and through the ground strap connected to the battery.  When the engine is running, with the generator charging, the generator provides the ignition current to the ammeter.  Then the primary circuit flow is the same as above.

        The distributor has two functions:  1. To switch the current supplying the coil's primary windings on and off, and 2.  To distribute the coil's high voltage secondary output to the spark plugs.  The breaker points switch the primary circuit.  The distributor's secondary current consists of rotor and cap (for the high tension spark plug wires).  When the rotor turns, it connects the center of the cap with the outside terminals of the cap, so the high voltage from the coil is directed to the spark plugs in the car's correct firing order.

        The condenser's basic purpose is to provide a cut off of current flow when the points are open.  Without the condenser, induced current  in the primary would flow across the point gap and would rob the coil's energy, causing no spark at the plugs.  The condenser also keeps the contact points from arcing,  because it momentarily provides a place for the current to flow as the points move apart.

        Spark plugs provide a spark gap inside the engine cylinders.  When the engine is running, the high voltage produced by the coil arcs across the spark plug gap, creating a spark that ignites the air/fuel mixture in the cylinders.  

        Before we set our distributor back into place, we set our harmonic balancer on 6 degrees BTDC (compression stroke).  Distributors are driven by a gear on a camshaft.  Most distributors have a gear on the lower side of the unit and some sort of a drive to engage the oil pump.  Our Packard has a drive on the top of the oil pump with a slot to drive the distributor.  This works very well because once you set the shaft in time, it stays in place.  Thus, when the distributor is installed, it's either in time or it's 180 degrees out.  Using the Packard manual tune up specs, we know that #1 plug wire needed to be at 6 o'clock, and we made sure the slot in the oil pump was in a vertical position.  Having already installed the points and setting them at .017, we  put on the rotor, turned it to 6 o'clock, and set the distributor in.  After aligning the index marks on the distributor hold-down plate to zero, we tightened the two bolts, then loosened the distributor lock screw to free it from the plate, allowing the distributor to turn freely.  At this point, our ignition wiring on the car was not ready to be connected, so we static-timed the engine by using a digital multimeter.  We set it on continuity, connecting one lead to ground and the other lead to the insulated side of the points.  We retarded the distributor until the points were closed.  In this position, the rotor had not yet reached #1 plug wire.  The points being closed created continuity, making the tester buzz.  We slowly turned the distributor into the rotor rotation (counter-clockwise) until the points just opened.  This break in continuity caused the multimeter buzzing to stop.  The distributor now was in time and we tightened down the lock screw on the hold-down plate.

        Checking the Vacuum Advance is important during a tune up.  We had ours rebuilt and tested it before putting it on the car by using a vacuum tester, running a vacuum hose to the unit an dafter pulling vacuum, watching the gauge to see if it held.  It did.  One sign of a bad unit is that at speed, the car doesn't have any power.  It struggles to reach top speed.  When we road-tested the car after tune up, we experienced this problem.  When we checked it again with the unit on the car, it would not hold vacuum.  When it was installed, the vacuum line nut-to-unit was one turn loose.  No white tape had been used on the line nuts (one at the carburetor and one at the distributor).  With this corrected, we tested again by using the tester at the carburetor end of the vacuum line.  It held!

        All of us at Southern Wheels Magazine wish you and your families a very Merry Christmas and a Happy and Prosperous 2013, so we can keep 'em driving!