There are many types of LS pulley kits available. From cheap but bulky junkyard parts to compact, mid-mount systems, price and performance can vary greatly. LS enthusiasts spend more time thinking about cylinder heads and fuel injection rather than pulley kits. When you consider it, however, your LS engine's accessory drive is crucial to the performance and reliability of your engine.

LS Serpentine Kit - The crossroads of many vehicle systems.

Your car or truck's cooling system and steering system, along with every electrical system, all intersect at your engine's accessory drive.  The vehicle may start up and drive without a properly functioning accessory drive, but it won't get very far.

Charging System Considerations - Not all alternators are created equal.

The best LS engine management system or electric fuel system is dependent on a high-amp alternator that can keep itself cool.  If you are considering an aftermarket system, keep in mind that some brands still provide old-school 12SI or CS130 alternators. These older alternators produce less amperage and are prone to heat-related failures due to their inferior cooling design. A low-budget pulley kit probably has a cheap alternator that will quickly wear itself out.

Premium LS pulley kits, such as those from Holley®, Wegner Automotive®, and Concept One Pulley Systems®, feature more modern CS130D, AD244, or HPR-type alternators. These units deliver more amps and are more reliable than older 12SI and CS130 alternators. It's essential to research your car or truck's electrical requirements to ensure adequate charging.  Factor in electric fans, EFI, HVAC, lighting, audio equipment, and powered conveniences such as power windows and heated seats. If you try to save money by choosing a budget LS pulley kit with an older 12SI or CS130, it may be impossible to upgrade the alternator at a later date while maintaining pulley alignment.  

Alternator Output - Does a high RPM solution exist for LS engines?

If your LS engine's RPM exceeds 6000 RPM regularly and/or for extended periods, a custom solution is required.  Most alternators have an 18,000 rpm redline. With a typical 3:1 pulley ratio, it is easy to overspeed an alternator. Pulley ratios can be adjusted to slow down the alternator. A larger alternator pulley is usually part of the equation. Slowing down the alternator, however, can negatively impact voltage output at idle. A higher-output alternator, such as an HPR or AD244, is employed to increase charging at idle.  While most manufacturers quote peak amp output, it is critical to check idle amp output before ordering an LS pulley kit.

Power steering feel and feedback 

Steering is obviously a critical safety system. When choosing an LS serpentine kit, don't underestimate the importance of steering feel and feedback. Your hands are in constant contact with your steering wheel. You should enjoy the driving experience. It's not only about comfort, feel and feedback keep you safe and help you drive faster in performance driving scenarios. 

Unfortunately, almost all accessory drive manufacturers offer a one-size-fits-all power steering pump with their accessory drive system. To get the most from your LS pulley kit, work with a manufacturer that will calibrate your power steering pump's pressure and flow to match your steering gear type and driving preferences. To our knowledge, Concept One Pulley Systems® is the only company that can dial in your power steering pump to match your steering gear.

LS Pulley Kit Bracket Strength - Front and rear support is essential. 

There are some LS pulley kits on the market that mount to your engine by way of a single, thin plate attached to the front of the water pump. Most of these designs have decorative windows cut into critical areas. No brackets are supporting the rear of the heavy accessory drive components. Fewer brackets result in a lower price, but does it also sacrifice strength? 

Despite being compact, an SD-7 AC compressor weighs 10 pounds dry.  That's pretty heavy. Now consider that the design has seven pistons that punch back and forth inside the unit, and a serpentine belt pulling downward on the front of the unit. To counteract the AC compressor's weight and dynamic loads, the unit must be supported at both ends.

Actually, top serpentine kit manufacturers, such as Billet Specialties®, Holley®, and Concept One Pulley Systems®, support the AC compressor in three places. While the added support may cost a little more, the added strength pays off in the form of long term reliability.

What is a mid-mount LS Pulley Kit?

With so many LS swaps underway, one of the most important questions is "Will the accessory drive fit my chassis?" Junkyard take-off systems are inherently bulky and chassis specific. Some aftermarket systems mount the accessories outboard of the LS engine's dimensions. Mid-mount pulley kits attempt to mount accessories as close to engine centerline as possible for maximum chassis clearance.

A great mid-mount design serves many purposes.  For example, upper drive components such as the AC compressor and alternator are mounted low. This lowers the center of gravity and provides an unobstructed view of the valve covers and intake manifold. That may sound trivial, but as enthusiasts, we like to celebrate the appearance of healthy V8 engines.

Moving downward, the power steering pump and and tensioner need to be mounted as high as possible to improve chassis clearance.  Steering box to power steering pulley clearance can be especially challenging with LS swaps. Choose an LS pulley kit where the power steering pump is mounted as high as possible and be conscious of pulley diameter, as well. On the right side of your LS engine, water outlet orientation is a concern.  Smart LS serpentine kit manufacturers typically offer thermostat housings that point straight down for improved frame rail clearance.

LS Serpentine Kit: 6-rib or 8-rib belt? and how much belt wrap?

There is no one-size-fits-all answer to either of these questions. First, it's important to remember that a 6-rib belt provides at least 5X more grip and significantly better load distribution than an old V-belt. For an LS pulley kit, horsepower and rpm play critical roles in determining whether or not to choose an 8-rib system with extra belt wrap.  500 horsepower and 5000 rpm are good thresholds for an LS engine.

Below these thresholds, a 6-rib LS serpentine kit with 90-plus degrees of belt wrap at the crank pulley is more than adequate. Above these thresholds, choose an 8-rib system with at least 180 degrees of belt wrap at the crank pulley. A well placed idler near the crank pulley will increase belt wrap with minimal changes to the pulley kit configuration.  A heavy-duty tensioner with a higher rate spring is also recommended.

The load characteristics for an LS power steering pulley are unique since maximum load occurs when the steering wheel is turned. The steering wheel is turned more at low engine speeds. A 6-rib system with less belt wrap works well for a street cruiser with a 400HP 5.3L LS. Too much belt wrap may yield parasitic loss in this mild application. Conversely, an 8-rib LS pulley kit with 180 degrees of belt wrap is recommended for a 700-plus horsepower autocross car where the steering wheel is aggressively turned, regardless of rpm. 

Links and References:

Serpentine vs V-Belt - Which is better

LS Pulley Kit - Concept One Pulley Systems®

Holley® GM Accessory Drive Kits

Billet Specialties® Accessory Drives