Project Snake - AK 427 Cobra Build Blog: Cooling Fan

Installation of the radiator and cooling fan was a reasonably straightforward job.

I had purchased the AK aluminium radiator when I was up at their open day last September; as they had one in stock it seemed rude not to take it away with me!

I went for a Davies Craig 16-inch unit from Merlin Motorsport for the cooling fan. This pulls a huge 2120cfm so it should keep my LS7 nice and cool.

The first step was to install the lower radiator mount, which is supplied as part of the AK chassis kit and is fitted with 4No. M8 bolts, washers and nyloc nuts.

Lower radiator mount fitted

There are two pins on the bottom of the radiator which are approximately 10mm in diameter and 20mm in length. The proper way to sit the radiator onto the lower mount is to purchase some rubber top-hat washers; these slide over the pins and then locate the bottom of the radiator into the two 20mm diameter holes in the lower mount. Other builders have used a variety of alternative solutions including a couple different diameters of rubber or silicon hose to create the stepped bushing.

I knocked up a couple of top-hat bushes from some 30mm nylon bar which hopefully will do the job.

Two bushes machined from some nylon bar

Bush in place and keeping radiator from sitting directly onto lower mount

The upper radiator mount is attached to the top of the radiator using 2No. M6 bolts and washers and to the chassis using 2No. M12 bolts and washers. I needed to clean out the threads in the chassis mounts with an M12X1.75 tap to remove the powder coating before the bolts would thread in easily. The holes in the top radiator frame also needed some work with a file to remove the excess powder coat. Initially, I assembled the top mount and radiator to check the fit but did not fully tighten any of the bolts.

The Davies Craig fan comes with four mounting feet that can be installed in several locations around the perimeter; I was hoping that by using the topmost and bottommost locations I could fix the fan to the upper and lower radiator mounts and not have to rely on zip-ties to secure the fan to the radiator.

Fortunately, this was the case. I started with the holes in the upper radiator mount and drilled two 6mm diameter holes equidistant from the centre of the mount to match the spacing of the fan mounting holes. I then loosely fitted the fan to the top mount with a couple of M6x25mm cap-head screws and reassembled the radiator and top mount with the fan to locate the bottom holes for the fan in the lower mount. I put some tape on the lower mount before reassembly and used a broken 6mm drill bit to mark the tape at the hole locations. I then had to take the whole shebang apart again to drill the holes into the lower mount. These ended up being lower than I had anticipated but still allowed enough space to install the cap-head screws; I might have had a problem with a normal M6 bolt.

I could then fix the fan to the upper and lower radiator mounts using the M6 cap-head screws, washers and some nyloc nuts. I had to insert the cap-head screws the wrong way around from what I would have preferred to prevent the excess length of the screw from rubbing against the radiator; this meant that I had to tighten up the fan fixings fully before reinstalling the radiator. Luckily there was enough play in the mounts for this not to be a problem.