MSD HEAT Digital HEI Module with Adjustable Rev Limiter for GM 4-Pin Distributors 83647

If you're running a carbureted or non-computer-controlled GM engine and want reliable ignition performance without the complexity of modern systems, the MSD HEAT Digital HEI Module is a proven upgrade. With 8.5 amps of output and adjustable rev limiting built directly into the module, you gain precise control over spark energy and engine protection—all without breaking into your distributor. Whether you're tuning a street engine or managing RPM in a race application, this module delivers the consistency that separates good ignition systems from great ones.

• High Output Performance: 8.5 amp current delivery ensures strong, consistent spark energy across your entire RPM range for improved combustion efficiency
• Adjustable Rev Limiter: Set your rev limit externally between 5,000–10,000 RPM without removing the distributor cap, protecting your engine from over-rev damage
• Advanced Dwell Control: Precision dwell timing optimized for high-RPM performance and coil saturation, maintaining spark strength at speed
• Direct Fit Installation: Bolt-in design for non-computer-controlled (4-pin) HEI housings on most GM vehicles
• Dual Compatibility: Works with stock HEI and MSD Pro-Billet HEI distributors, offering flexibility across builds
• 12V Operation: Designed for standard automotive electrical systems
• Compact Design: 1.75" H × 6.05" W × 7.85" L
• Emissions Legal: EPA Code 1—street and competition legal in all 50 states
• Limited 1-Year Warranty: MSD-backed coverage