Inside Holley’s New Complete Mid-Mount Serpentine Accessory System

The Holley Corporation continues to develop new products to help Mopar enthusiasts fit a Gen III Hemi into vintage muscle cars and various Dodge trucks. The latest component is a complete Mid-Mount serpentine accessory system, which substantially tightens the distance between the belt-driven accessories.

The Mid-Mount system comes with everything needed for a complete installation. The system includes a water pump, AC compressor, alternator, power steering pump, and crank damper. Also included are the accessory pulleys and a serpentine belt. In addition, Holley added heater hose adapters, power steering hose to -6 AN hardlines, and an alternator wiring harness.

Above: Holley has made great strides in developing engine swap installation components for the Gen III Hemi. Holley’s latest part is a Mid-Mount Serpentine Accessory System. The new system brings the pulleys closer to the engine’s center, which eliminates accessory interference with the chassis or hood.

Holley’s drive system resolves the alternator and frame rail or hood clearance concerns. In addition, to protect the steering boxes found on older vehicles, Holley reduces the power steering pressure to establish the proper assist without damaging the steering box.

The Holley Mid-Mount system is designed to fit the 2003-2008 5.7L, 2005-2010 6.1L, and 2007-2010 6.4L (Mopar Crate Engine) non-VVT Hemis (part no. 20-290BK (black finish) or 20-290 (cast aluminum)) or the 2009-2021 5.7L and 2011-2021 6.4L VVT Hemis (part no. 20-291BK (black finish) or 20-291 (cast aluminum)).

Above Left: The non-VVT Hemi timing cover is the mounting point for all the accessories. The cover can be ordered in cast aluminum or finished in black. Above Right: Included with the cover are all the parts necessary to finish the installation. 

The key part of the bracketless mounting system is the integrated timing cover casting that provides attaching provisions for each accessory. With the mounting points on the cover, the pulley locations are closer to each other, thus narrowing the width of the belt path.

Another benefit of the Mid-Mount system is the easy heater hose connection options, allowing maximum hose routing flexibility. The included alternator is a 150-amp unit with a wiring harness and does not rely on the factory ECU to excite the alternator.


Above Left: For the VVT Hemis, Holley designed a timing cover for those engines. Above Right: Like the non-VVT engines, the VVT system comes complete with everything necessary to complete the installation.

The water pump is serviceable without removing the timing cover. A compact Type II style power steering pump with a baffled reservoir is ideal for areas where space is at a premium. The Sanden AC compressor is a small, lightweight construction that fits in the tightest engine bay.

The engine coolant inlet and outlet swivel to allow for custom radiator hose routing from the engine to the radiator. An original equipment-style engine damper is cast with a serpentine pulley, and all the included pulleys maintain the stock ratios to maintain the optimal factory performance.

Above: The Mid-Mount accessory system provides a compact belt routing, which allows the Hemi to fit into nearly any engine bay. The pulleys have the factory dimensions, so the stock ratios between the crank damper and the accessories retain the factory-designed performance.

The Holley Mid-Mount system does not require spacers or adapters to fit the Hemi, which significantly reduces the complexity of the installation. Lastly, all the gaskets, seals, wiring, and plumbing adapters are included with the system. With everything included, all you need to do is decide whether the cast natural aluminum or black finish matches your car’s theme.

Through the entire engineering process, the Holley employees took the time to make the Mid-Mount an easy-to-install accessory drive system. Additionally, Holley includes color instructions to guide you through the stress-free installation. For more information about the Mid-Mount accessory system or any Holley Hemi installation components, check out Holley online or give its reps a call.

001---Non-VVT---Fits-2003-2008-5 002---Non-VVT---Fits-2003-2008-5.7L-&-2005-2010-6.1L-Engines--Black-Finish---Factory-Style-Damper 004----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6.4L-Engines---Black-Finish---Factory-Style-Damper 005----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6 009----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6.4L-Engines---Black-Finish---Factory-Style-Damper 008----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6.4L-Engines---Black-Finish---Factory-Style-Damper 007----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6.4L-Engines---Black-Finish---Factory-Style-Damper 006----VVT---Fits-2009-&-Up-5.7L-&-2011-&-Up-6.4L-Engines---Natural-Finish---Factory-Style-Damper

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Chris Holley

Technical Contributor Chris has been a college professor for 25 years; at Pennsylvania College of Technology in Williamsport, PA. for the last 20 years. Chris instructs automotive classes in HVAC, electrical/electronics, and high-performance, including using a chassis dyno, flow benches, and various machining equipment. Recently, he added a vintage vehicle upholstery class to his teaching assignments. Chris owns a '67 Dart, a '75 Dart, a '06 Charger, and a '12 Cummins turbo diesel Ram, and he is a multi-time track champion (drag racing) with his '69 340 Dart, which he has owned for 34 years.

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