 There are two LEDs inside...  There are two LEDs inside the interface module. The red one (LED2) shown will light every time there is a trigger signal. The green LED (not shown) indicates the box is on and receiving power. The red LED is critical in setting individual timing on a spin fixture. The circuits are encased in a clear epoxy so there can be no fudging with the circuitry. |  An overhead view of the mounted...  An overhead view of the mounted Zero-Cross with the cap and rotor removed. |  Tucked inside a Chevrolet...  Tucked inside a Chevrolet engine, it's hard to tell what your opponent's running (another advantage to the distributor at the back of the engine). This Zero-Cross fit very nicely in an engine at the Hendrick Motorsports shop. |
Compromise Aftermarket electronic ignitions have progressed quite a bit since 1992. You can now buy retrofit digital ignition systems that permit ignition timing curve programming via a laptop. Unfortunately, most stock car racing series still don't allow such digital manipulation of ignition timing. However, you can now find a mechanical equivalent as MSD is offering the Zero-Cross Pro Billet distributor.
This racing ignition distributor allows you to adjust the ignition timing for separate cylinders by incorporating a reluctor assembly with eight individual magnetic trigger arms that can be advanced or retarded as needed. They can be adjusted 0-6 degrees of crankshaft timing. No laptop is needed, just a feeler gauge.
Cleverly enough, this individual cylinder timing control is packaged in the race-proven billet housing and uses a large cap and rotor assembly, so it's not directly obvious that you're running a distributor that has such adjustable timing precision inside. You don't have to set a fixed, compromised ignition timing for all the cylinders, but can individually manage timing in each cylinder for best output before engine knock occurs.
The Zero-Cross distributor is designed for full-on racing applications and has some interesting performance features besides the individual cylinder timing control. The housing is CNC machined aluminum billet and uses a sintered bushing at the housing's bottom and a precision 1.587-inch instrument grade bearing at its top to accurately locate the distributor shaft at all rpm.
The Zero-Cross distributor has redundant ignition pickups stacked atop each other so you can switch from a primary to secondary ignition control unit while retaining the custom cylinder-to-cylinder timing (unlike the situation that would occur if the primary and secondary pickups were wired 180-degrees apart). The secondary pickup is also adjustable. You can set it to take out two degrees of ignition timing, for example, from all of the individually-timed cylinders when you switch to the back-up ignition. If you're wondering why you'd do this, one possibility might be reducing the overall engine output late in a race when the track is all greasy, which would help keep the tires hooked up. You could think of it as a sort of mechanically-governed traction assistance.
There is no centrifugal or vacuum ignition timing advance in this racing part. The distributor requires an interface control box for each of the two pickups to condition its uniquely stable trigger signal so it can activate current MSD ignition controls and maintain complete redundancy.
Available for Chevrolet, Ford, and Chrysler V-8 engines, the Zero-Cross has made its way legally into the Winston Cup Series and can be found on many race-winning teams. It has been seen in some top dirt Late Models as well as DIRT Modifieds in action in 2003.
The distributor is designed to be rebuilt and teams can do their own maintenance and repair. MSD offers replacement/repair kits for the entire distributor. CT
(Editor's Note: Special thanks to Hendrick Motorsports and Dale Earnhardt Inc. for help on this story.)
Chevrolet Distributor: 83971
Ford 351W Distributor: 83951
Chrysler R5 Distributor: 85911
Interface Control Box: 83581