Installing an ignition that’ll give our Sprite the spark it deserves

Doesn’t the rebuilt, supercharged 1275 with headers in our Bugeye Sprite deserve some spark?  We had already had our distributor reworked by Advanced Distributors in Minnesota, removing the points and recurving the advance. Why not install that MSD 6AL that’s been sitting on the shelf for a few years waiting for just the right project? 

This shelf in front of the battery fits our MSD box perfectly. Photography Credit: Tim Murrary

We have been fans of MSD ignitions for many years, and the bright red boxes can be found under the hoods of many of the staff here at Classic Motorsports. 

The 6AL seemed like the perfect addition to the Bugeye. To paraphrase MSD, it is first and foremost a capacitive discharge device. The ignition system on the Sprite is an inductive ignition, meaning the coil must store and step up the voltage to maximum strength in between each firing.

At higher rpm, since there is less time to charge the coil to full capacity, the voltage falls short of reaching maximum energy which results in a loss of power or top-end miss. 

The MSD features a capacitor that is quickly charged with 520-535 volts, storing them until the ignition is triggered. With the CD design, the voltage sent to the coil positive terminal is always at full power even at high rpm. 

Additional benefits include a rev limiter, which is easily adjustable from the top of the MSD unit, and electronic tach output which was important since we lost our mechanical tach drive with the distributor rebuild. 

The hardest part of the installation was determining where to locate the MSD box itself. 

Since there was a nice shelf in front of the battery tray, with convenient access to all our wiring, we decided to mount it there–MSD includes a mounting bracket which simplifies locating and mounting the box. 

As mentioned in previous installments, we created a modified Bugeye wiring diagram and the MSD was part of that redesign from the get-go. 

Using MSD’s excellent wiring instructions, we were able to make-up sub-harnesses to connect the MSD to the chassis wiring harness and make external connections to the battery (via a circuit breaker), the tach, switched power, and the coil. 

The result, while admittedly not stock, is neat and tidy and we are exceptionally happy with the way it turned out so far.  Stay tuned for the road test where we’ll see whether that additional spark results in additional fun. 

Our MSD wiring looks neat and tidy.  Per MSD, the 6AL can be mounted in the engine compartment if it is away from direct engine heat. Photography Credit: Tim Murray

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