MSD GM HEI Ignition Coil 42kV 70:1 Turns Ratio 0.31 Ohm Primary Resistance 8225

If you're running a classic GM HEI distributor and want to maximize spark energy without a complete ignition system overhaul, the MSD 8225 coil is a direct bolt-on upgrade that delivers measurable gains in combustion efficiency and RPM capability. The 70:1 turns ratio and ultra-low 0.31-ohm primary resistance generate 42,000 volts of consistent spark output, enabling reliable ignition all the way to 9,000 RPM—essential for both street and competition builds. When paired with the MSD HEI Module (PN 83647), you get full-power sparks at high RPM, eliminating weak ignition as a bottleneck in your engine's performance envelope.

• Direct GM HEI replacement
• 70:1 turns ratio
• 42,000 volts maximum output
• 0.31 ohm primary resistance
• 9.2K ohm secondary resistance
• Full power to 9,000 RPM
• 3.5 mH inductance
• 200 mA peak current
• 200 µs spark duration
• Epoxy-filled construction
• CARB E.O. approved
• Bolt-on installation
• 1-year limited warranty