Specifications

INSTALLATION INSTRUCTIONS 3
MSD IGNITION • 1490 HENRY BRENNAN DR., EL PASO, TEXAS 79936 • [phone] • FAX [phone]
As you can see from the chart, most factors will change throughout the range of the engine operation.
The Digital E-Curve allows you to make timing changes based on these factors.
Example: An engine has 11:1 compression, a high energy ignition and turns 5,500 rpm. With the
specifications given, you will have to retard the timing for the high compression and high energy
ignition. By comparing the engine’s specifications against the chart, a usable timing guideline can
be found. Engines with a combination of items from both columns will require a timing that is set
in the mid range.
Obviously a full technical explanation of correct ignition timing would be very complicated. The
best way to arrive at a suitable ignition curve for your engine is to use the Ignition Timing Factors
Chart as a guide and compare it to the Advance Graphs in Figure 3 until a suitable curve is found.
When selecting your advance curve, use detonation (engine ping) as an indicator of too much
advance, and a decrease in power as an indicator of too little advance. Also consider how the
engine cranks and starts. Too much advance can cause an engine to crank slow or even kick
back. Here are a couple of suggestions.
• Use as much initial advance as possible without encountering excessive starter load.
• Start the electrical advance just above the idle rpm.
• Select an advance curve that produces good acceleration without detonation.
SETTING UP THE DISTRIBUTOR
Once you have determined your desired total timing, you’ll need to select the electronic advance
curve that you want to run (Review the information on page 2 to help choose a curve that matches
your needs). The charts in Figure 3 show all of the different timing curves available. Note that a
letter is given to the curve. Refer to the chart in Figure 4 using this letter to determine the position of
the two rotary dials. If you plan to take advantage of a vacuum advance, select the vacuum curve
number and cross reference it with the mechanical curve’s key letter to get the switch positions.
For example: If you want a 20° curve that advances slowly, select curve E. This means you would
put Rotary Switch 1 in position “0” and Switch 2 in position “5”. If you choose no vacuum advance,
simply do not connect the vacuum port. In this example, if you would prefer 10° of vacuum advance,
choose Vacuum Curve 3 and cross reference it to Timing Curve E. The switch positions would be
Switch 1 “4” and Switch 2 in “5”.