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How To Install A Holley Complete Mid-Mount Accessory Drive Kit

Author: Ryan Manson | 07/12/2021 < Back to Motor Life Home

Let's face it, there's nothing worse than dropping that freshly-built engine under the hood for the first time, only to find that the alternator contacts one inner fender, the power steering pump whacks the crossmember, and the A/C compressor hits the other inner fender. Those big buck bracket kits can often times locate the accessories way out in the breeze, causing all kinds of fitment problems. It was these clearance issues that have frustrated builders for years that were in mind when Holley designed their new small block Chevy Mid-Mount Complete Accessory System.


Designed around a bespoke aluminum water pump manifold assembly, the Holley Mid-Mount Kit features a "bracket-less" design, with the accessories attaching directly to the water pump housing itself. This results in a more compact system, pulling the accessories in tighter than traditional designs, increasing the clearance often needed in tight engine compartments. A myriad of features, including many adapted from the C7 Corvette’s LT1 drive system, allows the Holley Mid-Mount Kit to not only solve the issues that crop up when shoe horning a larger engine in a tight engine compartment, it also incorporates modern technology in a simple design that cleans up any engine bay.

Mid-Mount Engine Beauty Shot

Here's our 377ci engine, fully dressed in Holley parts, ready for the installation of their Small Block Chevy Mid-Mount Complete Accessory System (20-240BK).


Mid-Mount water pump

Holley's unique water pump manifold assembly incorporates all the mounting points for the alternator, power steering pump, and a/c compressor, without the need of any additional brackets and is the key to the kit's design. A C7 Corvette bolt-in water pump is just one of the many innovations incorporated within the kit.


Mid-Mount water pump seals

While the front of the water pump manifold is completely unique, the backside is familiar small block Chevy fare, but with a twist. Holley's water pump housing is machined to use O-ring seals as opposed to the traditional gaskets.


mid-mount kit hardware

All the hardware required to install the water pump, manifold assembly, and all the accessories are included in the kit.


mid-mount bolting up water pump

A total of six fasteners are used to fasten the water pump manifold assembly to the block.


mid mount water pump bolts 2

Four upper bolts attach to the traditional water pump mounting points, with two additional fasteners at the bottom of the manifold.


mid mount fasteners torque

The six mounting fasteners get torqued to 30 ft/lbs.


Mid Mount water pump install

With the water pump manifold in place, the LT1 cartridge-style water pump can be installed using the provided M6 button head bolts.


Mid Mount alternator

A compact A/C compressor and Type II power steering pump are standard fare, but the Holley alternator is pretty special. Designed in-house by Holley engineers, this premium alternator utilizes 6-phase technology, again found on C7 Corvettes, and features 150 AMP output, packaged in a compact, fully sculpted, all aluminum housing.


mid mount alternator installation

Installation of the accessories begins with the alternator, using the provided M10 x 80 button head bolts, fastened to 36 ft-lbs.


mid-mount power steering pulley

Next, the power steering pulley is installed on the Type II pump using a pulley installation tool. When the pump shaft and pulley hub are perfectly flush, installation is complete.


mid mount power steering pump

The power steering pump attaches to the water pump manifold using a trio of M8 x 30 flange head fasteners, torqued to 18 ft-lbs.


mid mount A/C compressor

The water pump manifold features unique machining that allows the A/C compressor to slide into place, without the fasteners fouling on the cylinder head or valve cover. One M8 x 95 flange head bolt is started on the inner set of A/C compressor ears and slid into place on the water pump manifold.


mid mount second a/c fastener

The second M8 x 95 fastener is then partially installed through the outer, rear compressor mounting ear and the compressor then rotated into place on the water pump manifold. After assembly, each M8 fastener is then torqued to 18 ft-lbs.


mid-mount a/c shipping plate removal

The shipping plate on the A/C compressor is then replaced with this machined aluminum piece using the provided O-rings and M8 x 18 socket head bolts.


mid-mount belt tensioner

The belt tensioner is then installed next, using an M8 x 70 button head bolt and washer.


mid-mount serpentine belt

By rotating the belt tensioner using a 1/2-inch square drive breaker bar, the six-rib serpentine belt can now be routed and installed.


mid mount a/c cover

The last portion of the installation has to do with dressing up the front of the accessories, beginning with the A/C compressor clutch cover. Three 1/4-20 x 3/4-inch flat head fasteners are used to secure the clutch cover, torqued to 6 ft-lbs.


mid-mount alternator cover final

The cover is then simply pressed into service and held fast by the O-ring.


mid-mount tensioner cover

The tensioner cover is the last piece of the puzzle to our installation and features a retaining plate, cover, and a pair of M3 x 0.5 x 20 button head fasteners.


mid mount tensioner cover 2

The retaining plate is first rotated into position behind the tensioner body.


mid mount tensioner cover 3

The cover is then attached using the provided hardware. About 9 in-lbs is all that's required to hold the cover in place.


mid-mount complete

That's a wrap! As you can see, the accessories are tucked in nice and tight against the heads and sit lower that the valve covers. The all black finish should look great for many thousands of miles and will be easy to simply wipe clean when things get a bit grubby.


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