Deep Dive: Holley's Gen III Hemi Mid-Mount Accessory Drive

10 min read

Deep Dive: Holley's Gen III Hemi Mid-Mount Accessory Drive

10 min read

After nearly two decades in production – and with more examples continuing to hit the streets of America every single day – the third-generation Hemi V8 is becoming an increasingly attractive engine swaps for old school muscle cars, trucks, and just about anything else that could benefit from a healthy dose of modern Mopar horsepower.

But as is often the case with modern V8 transplants, there are a few things that would-be builders need to consider in order to ensure their project’s success, and the engine accessories are among those. “When we started doing our development with the factory accessory drives, we ran into a couple of problems,” explains Jim Szilagyi of Holley Performance. “We discovered that the OE alternator was tough to use – it uses pulse width modulation and you needed the factory ECM to control it, and there were also situations where we ran into clearance issues. So about a year ago we developed some mounting components to modify the production accessory drive system so builders could use a different alternator, along with another kit that would allow you to relocate the factory alternator.”

Holley engineers also identified other potential obstacles with Gen III Hemi swaps and sought to address those as well, which in turn led to the development of their new mid-mount accessory drives.

“We learned a lot with the development of the accessory drive systems for the LS engines,” Szilagyi says. “For that platform we did a high-mount-style system, a low-mount, and a mid-mount. And it was clear that the mid-mount was the most popular design – it’s just a really streamlined setup that looks slick and tucks everything in really tight for better clearance. So after running into several different clearance issues with the Hemi swaps we were doing, we decided to take that approach with this new accessory drive system design.”

Multiple Considerations, One Solution

Gen III Hemi Mid-Mount beauty shot

The Gen III Hemi Mid-Mount Accessory kits come in two basic finishes: natural cast and black. Both finishes are available for both VVT and non-VVT engine designs.

Primarily aimed at street-driven builds – projects where creature comforts like air conditioning and power steering are often part of the mix – these mid-mount kits address a range of challenges that builders face when swapping a modern Hemi into an older vehicle while also sprucing up the engine bay.

The system utilizes a patent-pending "bracketless" design where the accessories bolt directly to the timing cover for a cleaner look that draws attention to the engine itself rather than the accessories that are bolted to it. “There’s definitely an aesthetic benefit,” Szilagyi points out. “You’ve got these finishes that give the components a modern look, and with everything tucked together the way that the mid-mount system is designed, it looks more attractive than the traditional layout.”

Gen III Hemi Mid-Mount Layout

The main component of the Gen III Hemi Mid-Mount Accessory Kit design is the "bracketless" water pump housing. From there, accessories like the cartridge-style water pump, alternator, air conditioning compressor, and the power steering pump bolt directly on, keeping the accessories nice and close to the center of the engine.

But more importantly, the mid-mount accessory drive also solves several problems that could otherwise stop a Gen III Hemi swap project in its tracks. Modern Hemi engines utilize two different factory accessory drive designs: One designed for trucks (which were the first applications for the Gen III Hemi and took advantage of the tall engine bays in those vehicles) and the other for passenger cars like the Charger and Challenger that came later, which necessitated relocating the alternator elsewhere to make everything fit. Both designs can cause clearance issues in engine swap projects for different reasons.

“Say, for example, you get a 5.7-liter Hemi out a truck and you try to put it in an old A-Body, B-Body, or E-Body,” Szilagyi says. “The hood is going to hit the alternator when you try to close it when the alternator is mounted in the factory location. The other common clearance issue we see with some applications is with the car-style factory accessory drive. That design puts the alternator low on the passenger side of the engine bay, and that can get into the frame rail on some vehicles.”

Holley engineers also had other factors to consider during development, like the variable valve timing feature that was introduced back in 2009 on the 5.7-liter engine. “With the exception of the 6.1-liter Hemi, everything moved to VVT after that,” he notes. “And that means that the accessory drive systems are different for the VVT and non-VVT engines because the timing covers are different – they’ve got the phaser on the end of the camshaft with VVT engines, so we needed to add a little bit more room to accommodate that.”

Gen III Hemi Mid-Mount Power Steering Pump

The power steering pump that comes with the Gen III Hemi Mid-Mount Kit is designed to work at the lower operating pressures that older steering box designs can cope with. This is also a handy way to avoid electrically-assisted power steering units found in newer vehicles.

The factory power steering system can also present some hurdles for engine swaps as well. “The factory power steering pump on a Gen III Hemi makes about 1600 psi of pressure, and it turns out that it’s just too much pressure for an older muscle car or truck. When we developed our Gen III Hemi swap kits, we started noticing that the system was blowing out the seals on steering boxes. It was probably 400 or 500 psi too much pressure for what a typical power steering system on an older vehicle was originally designed for.”

To resolve the issue, Holley also includes a power steering pump with the correct pressure in each mid-mount accessory drive kit. “It’s the same power steering pump that we use with our other engine platforms. Almost every power steering pump you’ll find on a V8 engine is a Saginaw Type 2, and this is different version of that pump with the correct pressure for those older steering box designs.” It’s also worth noting that these power steering pumps can come in handy with newer Hemi engines that utilize electrically-assisted power steering systems, as those engines do not include a hydraulic power steering pump to begin with.

To take out multiple birds with one stone, the Gen III Hemi mid-mount accessory drive kits come with everything you’ll need to get the engine outfitted for the swap: The 150 amp alternator, power steering pump, SD7 AC compressor, compact Holley water pump, pulleys, belts, requisite hardware, and the timing cover are all included to make this a one-part-number type of operation.

Options and Upgrades

Gen III Hemi mid-mount kit

The Gen III Hemi Mid-Mount Accessory systems come standard with a cast-iron damper with the pulley cast into it, with an ATI Performance SFI-certified damper and billet aluminum pulley available as an option.

For customers that would prefer not to get the entire mid-mount accessory drive kit, Holley also offers a retrofit kit to put a lower pressure power steering pump on a truck-style factory accessory drive system, as well as the aforementioned relocation and retrofit options for the alternator. Replacement parts for the accessory drive systems – like the timing cover, damper, the belt-driven accessories, and even gaskets and bolts – can be ordered individually as well.

The mid-mount accessory drive systems are available in as-cast aluminum as well as black finishes for both VVT and non-VVT engines, and for those who plan to go racing with their Gen III Hemi-swapped vehicle, Holley has a purpose-built solution for them as well.

Gen III Hemi Mid-Mount A/C Compressor

The air conditioning compressor is a Sanden SD7 unit that is compact and powerful.

“It’s a complete kit that’s very similar to our standard VVT and non-VVT mid-mount accessory drives for this engine platform, but it comes with an SFI-rated damper and a billet aluminum crank pulley,” Szilagyi says. “The standard kit uses a cast iron damper with the pulley cast into it, whereas this damper comes from ATI Performance and is tested to a higher RPM. And since it doesn’t have a pulley cast into it, we developed one made from billet aluminum to pair with it that has a black anodized finish. So not only are these components a bit lighter and motorsport-ready, they’re also more attractive to look at.”

All told, there are eight different mid-mount accessory drive kit options available for Gen III Hemi swaps – one of which likely ticks all of the boxes for your next project. And they’re all available now.

Gen III Hemi Mid-Mount on the stand


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