Mechman 240A 1963-1985 GM Replacement Alternator


240A 1963-1985 GM 10DN, 10SI, 12SI Replacement


  • Idle Output – 140 Amps
  • Cruise Output – 240 Amps
  • 2 1/2″ diameter single V pulley

Note: Output graph is plotted with a 7″ diameter crankshaft pulley.

Available in natural, satin black, polished, and chrome finishes.

Complete description below.



This is the 170A unit’s larger brother. The 240A unit makes greater output above 800 engine RPM (2,400 Alternator RPM) and the 170A unit makes greater output below 800 engine RPM plain and simple.

Mechman “Hot Rod” Alternators

These are designed as direct replacements for 1963-1985 GM Vehicles originally fitted with a 10DN, 10SI, or 12SI alternator. They utilize 6-phase Hairpin stators which use less horsepower than traditional 3-phase designs. The following are the features of these outstanding units:

  • Bolt-in Replacement for 10DN, 10SI, or 12SI GM Alternators
  • Internally Regulated
  • Internal Fans
  • Available in 170A and 240A Sizes
  • Available in Natural, Polished, or Chrome Finish
  • 1-Wire Design with 400 RPM Self-Exciting Regulator**
  • Heavy Duty 5/16″ Output Stud
  • Fitted with V-belt Pulley
  • 2 Year Manufacturer’s Warranty

**Devout readers of Tony Candela’s books will note that he is not a fan of traditional 1-wire designs. That being said, Mechman has recently migrated to a 400 RPM Self-Exciting regulator that will not un-excite during extended periods of idling – the main draw back to traditional 1-wire designs. 3-wire regulator units are available at the same price via special order.

The 170A and 240A units share the same housing. Download a complete Hot Rod Alternator Drawing including all dimensions.

We recommend our 1/0 AWG Charging System Upgrade Kits or Big 3 Upgrade Kits for 240A units!


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