MSD 83647 HEAT Digital HEI Ignition Module with Built-In Rev Limiter

The MSD 83647 HEAT HEI Module is a high-output, drop-in replacement ignition module designed for non-computer-controlled GM High Energy Ignition (HEI) distributors. Using upgraded components, this digital module delivers significantly more coil drive current than a stock module, saturating the coil faster for a stronger spark at high engine speeds — resulting in improved power, extended rpm range, and better starting performance.

Unlike a standard replacement module, the HEAT HEI Module features a built-in adjustable rev limiter that can be set externally without removing the distributor cap, making on-the-fly rpm limit adjustments fast and convenient. The rev limiter is adjustable between 5,000 and 9,000 rpm, giving performance-oriented applications precise engine protection. Advanced dwell control further optimizes coil charge time for consistent, high-energy spark delivery across the entire rpm range.

Key Features:

• Produces 8.5 amps of coil drive current — significantly more than stock modules
• Advanced dwell control for improved high-rpm ignition output
• Built-in adjustable rev limiter settable from 5,000–9,000 rpm
• Adjust the rev limiter externally without removing the distributor cap
• Direct plug-in fit for non-computer-controlled 4-pin HEI housings with vacuum advance canister
• Compatible with factory, aftermarket, and MSD HEI distributors
• CARB Executive Order D-40-43 — legal for sale and use on emissions-controlled vehicles in all 50 states

The MSD 83647 is a direct replacement for all 4-pin modules used in HEI distributors. When paired with MSD's HEI coil, this module creates a potent high-energy ignition system capable of supporting performance builds up to 9,000 rpm. Sold individually.