The OEM alternators on the LT based engines offer a very high output compared to the LS alternators, ranging from 150 amps to a whopping 220 amps from the factory. The LT Truck and Camaro alternator is actually the same size as the LS truck alternator so they can be used with ICT Billet brackets designed for LS applications! Also, LT alternators maintained the same 2-pin connector as Gen IV LS truck alternators.

What This Means to You

The LT engine alternators offer a bigger selection of amperage needs for your build. If you have a simple setup that does not have a lot of electrical components, the basic 150A alternator is sufficient. If you have a setup that has a ton of electronics or a wall of subwoofers, these higher output OEM alternators should provide you plenty of juice. For more extreme cases, aftermarket units like Powermaster or Mechman LS/LT units will get it done! Check them out and integrate them into your build.

How To Calculate Amps Needed

Below is the most common items needed when running a fuel injection setup which equal about 110 amps:

• EFI Ignition System – 20 amps
• Headlights/Tail Lights – 15 amps
• Gauges – 5 amps
• Radio – 10 amps
• HVAC – 20 amps
• Electric Fuel Pump (each) – 10 amps
• Electric Fan (each) – 30 amps

Next are common items we see added to builds. Pair your total size with an alternator that is rated for that amperage:

• Transmission Fan – 25 amps
• Intercooler Pump – 15 amps
• Electric Water Pump – 20 amps
• Datalogger – 5 amps
• Transbrake – 15 amps
• Nitrous Solenoids (each) – 15 amps
• Nitrous Bottle Blanket – 20 amps
• Line Lock – 6 amps
• Scavenge Pump – 15 amps
• Electric Power Steering – 15 amps

Decoupler Pulleys

GM used decoupler pulleys on select high-end LT vehicles to reduce belt noise and protect the accessory drive system. These pulleys, also known as one-way clutches or overrunning alternator pulleys (OAP), allow the alternator to freewheel in one direction when engine RPM drops suddenly. This decoupling prevents the alternator’s heavy internal rotor from putting stress on the serpentine belt during quick deceleration.

This matters for a few reasons. On high-performance engines that rev up and down quickly, the alternator’s inertia can cause belt slap or loosen the belt when RPMs drop rapidly. The decoupler pulley eliminates that problem by letting the alternator spin freely instead of forcing the belt to absorb that load.

Decoupler pulleys also help smooth out vibrations. In a normal setup, the crankshaft’s power pulses are transferred into the belt drive, which can cause noise and wear on the tensioner. The one-way clutch absorbs those pulses, leading to quieter, smoother belt operation and longer belt life.

Another benefit is efficiency. When the alternator can overrun during deceleration, the engine doesn’t have to slow down as much rotational mass. That means less drag on the engine and slightly better fuel economy, especially in stop-and-go driving.

Overall, these pulleys reduce belt wear, lower vibration, prevent belt chirp or slippage, and extend the lifespan of both the alternator bearings and the tensioner. GM mainly used them on higher-end or performance LS models where rapid RPM changes are common.

Alternators We Recommend and Stock

Truck and Camaro 5.46" Pattern:
Powermaster 165 Amp
Mechman 240 Amp
Mechman 250 Amp Billet Case
Mechman 170 Amp Billet Case

Corvette 6.06" Pattern:
Powermaster 220 Amp

Feel free to Contact Us if you have any questions!