Preparing A Tiger To Live In The Arizona Desert
By Cullen Bennett
B9472658
September 15, 1999
Part Two; "The Fan of Life"
Once I had paid my money for the aluminum radiator, I wanted to get the most out of its potential performance that I could squeeze. There had been numerous references on the Tiger email chat forum to an elusive six bladed fan that Ford had made for some of the Canadian cars. The fan (C9DZ-8600-A) was however about 16" in diameter and too large to just drop into the Tiger. The center hole also needed to be opened up to a 1" diameter to fit the Tiger water pump. I bought one from a shop in the Redwood City area and set about trimming it down. First, carefully drill out the center hole using the existing hole as a pilot guide. Next, make up a pivot bushing to fit the 1" hole and put an axle through it to allow the fan to be rotated. Using a pair of digital calipers measure and mark each of the tempered aluminum blades to clear the rack and pinion housing. I believe the dimension was about a 15" diameter (I cut off about 1/2" on each blade - suite yourself). Using a power bandsaw and a pivot axle, carefully cut the blades off along the measurement lines. Using the axle as a pivot you can turn the fan and sand each blade until it runs true. It's really not all that hard to do (if your careful).
Part Three; "In search of the Holy Shroud"
A common folklore about the purpose of a fan shroud is that it is to keep unwary fingers out of the fan blades. Actually the shroud is probably one of the most under rated and misunderstood items under the hood (bonnet for the British folk). I have seen many a car at the shows with a beautifully polished brass radiator with a big glitzy chrome plated fan sitting behind it. It looks real nice, but doesn't work worth a damn for cooling. If air flow is left to chance, it will always take the path of least resistance, and that usually isn't where we would like to have it go, radiators provide resistance to air flow. In the ideal situation, a radiator should have a "partially sealed" compartment formed by the shroud behind the core which has the fan mounted in the only opening leaving this compartment. There are varying opinions as to just how much of the fan blades need to be sticking inside the compartment and how much outside to obtain optimal transfer of the air from inside the compartment to outside the compartment. I ended up with about 1/3 of the blade outside the shroud. It just sort of happened that way, after all there's not a lot of working room down there. When the air inside the compartment is moved outside, a low pressure area is formed inside. Outside air will immediately get sucked into the partial vacuum through the only available route which is through the radiator fins (provided the edges are sealed properly). The better the seal around the radiator edges the more force will be created to pull the air through the radiator. There are plenty of the spongy rubber seals that already have an adhesive backing available to do the job nicely. The Tiger, as it came from the factory, did not have a lower half to the fan shroud. Most of the air stirred about by the fan came from underneath the car and around the radiator. This "hole" beneath the car in front of the engine is practically the only decent air flow path out of the engine compartment due to the tight fit of everything else. In fact, some of the hot air coming out of the radiator and out of this "hole" can recirculate toward the front and get mixed with cooler incoming air and thereby reduce the cooling effect that could be possible. In my personal opinion, the missing lower half shroud is the number one item leading to poor cooling in the Tiger. When I set out to make the lower half of the shroud, I knew that there were compound bends involved in fitting around the fan blades and over the rack and pinion (R&P) housing and cutting a flat piece of sheet metal to fit was not going to be an easy task. Finally a light came on in the back of my head with a simpler solution. I headed off to the local drug store and found the rack of school supplies which included heavy construction cardboard (some people call it poster board). I bought a couple of sheets and headed back to the garage. I made the first cuts deliberately oversize just to get it to fit past the fan. Carefully, I marked the major obstructions with a pencil and cut them away one at a time and refitting the position after each cut and remarking. It took a couple of hours to get everything to line up just right. When you're doing it, be sure to leave sufficient overlap at the top edges to provide a place for sheet metal screws to attach from the original shroud to make it rigid. Another place to give special attention is to the area along the bottom of the radiator, and in front of the R&P. Once it all fits nice and snug, pull it out and lay it on the sheet metal as a pattern. Most ACE Hardware stores have a selection of sheet metal in the back. As best as I can remember, I used a 22 Gauge metal. It needs to be stiff enough to hold its shape when bent but not so stiff as to make it impossible to bend with your hands. By the way, a good pair of leather gloves will sure save your fingers while cutting the sheet metal. After cutting it out, use a hand file or sandpaper and take off all the sharp edges, and give it a good coat of primer and paint to suit your taste.
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