If you want to keep your hot rod running cool, it’s going to take more than a good radiator. You’ve got to move some air. You could have the largest, highest-flowing radiator money can buy, but if you’re unable to move sufficient air through it, you’re still in hot water.
Moving air is the fan’s job. Much valuable information has been written about choosing the most efficient fan type, size, and location. Richard Mikami chose a 14-1/2-inch-diameter mechanical fan for his big-block–powered ’32 Ford coupe. The fan is wide enough to cover the width of the radiator, but is unable to draw air from the upper portion of the 22-inch-tall core.
The solution is a fan shroud. Shrouds expand the size of the area from which a fan can draw cool air—in this case from a 14-1/2-inch circle to the entire surface area of the radiator. A secondary advantage is that they can shield the radiator from the heat from the engine—and provide a more finished look to the front of the engine compartment. The shroud on Mikami’s coupe was built by Brian Stone at Stone’s Metal Shop in Gardena, California. Stone took a little time (a lot of time actually) to really dress up this custom piece. The decorative screen treatment in the area above the fan opening doesn’t make the coupe run cooler, just look cooler.
The critical first step is...
The critical first step is measuring the radiator to determine the size of the shroud, and to find the fan position relative to the radiator, top and bottom. This fan blade diameter is 14-1/2 inches; Brian Stone will add a 1/2 inch all around for a shroud opening of 15-1/2 inches. The first measurement is to determine the distance from the bottom of the radiator to the bottom of that 15-1/2-inch opening. Left and right measurements are also made to see whether or not the fan is centered on the radiator.
Before any sheetmetal is cut,...
Before any sheetmetal is cut, a two-piece wooden clamping block is built. This will be used to form the shape of the aluminum shroud.
The opening was cut out with...
The opening was cut out with a jigsaw, then finished with aviation snips and filed.
At the very end, he finished...
At the very end, he finished this radius with an air hammer. Different hardnesses of rubber faces can be interchanged to smooth out the flange.
Instead of having sharp 90-degree...
Instead of having sharp 90-degree breaks, the inside and outside edges of the clamping black were rounded with a router, then sanded. This provides more flowing edges, making for a better-looking final piece.
To create the flange for the...
To create the flange for the fan opening, the inside radius needed to be stretched (outside radiuses are the opposite and need to be shrunk). Stone used the planishing hammer with a linear stretching die on the bottom to determine the shape. You can see it already taking shape. Stretching the sheetmetal now will make it easier to work with later. “Just like butter,” he says.
This custom tool (we’ve heard...
This custom tool (we’ve heard it called a wood slapper or a shillelagh) was used in the same way to form the outside flange around the shroud. The depth of the shroud is based on the position of the fan, which should be positioned approximately halfway into the opening.
The measurements are transferred...
The measurements are transferred to a flat sheet of 0.065-inch grade 3003-H14 aluminum, which is strong but relatively easy to shape. Stone added 3 inches around the perimeter, which will become the flange of the shroud. After finding the center point of the opening he marked out the circumference with a compass. He reduced the 15-1/2-inch circle by 1/4-inch in order to create a lip.
Sure enough, the aluminum...
Sure enough, the aluminum hardly puts up a fight. With the aluminum securely between the two pieces of the clamping form, Stone used several different sized soft hammers and mallets (such as rawhide, rubber, or copper) and several different wood or phenolic dollies to shape the aluminum. Stone doesn’t use a body hammer, which is hard and would mark up the metal. He worked slowly, moving from the top of the radius down, keeping it tight on the wooden form. By the time he finished, he’d made about 1,000 strikes.
Soft hammers and plenty of...
Soft hammers and plenty of patient forming was used to form the notch for the lower radiator hose. Some welding was required on the seams here.
Soft hammers and plenty of...
Soft hammers and plenty of patient forming was used to form the notch for the lower radiator hose. Some welding was required on the seams here.
At this point, the shroud...
At this point, the shroud is ready to do its job. There was still some metalwork to do to take it to the next level. The shroud was held with Cleco fasteners into a new clamping block (wood on one side, aluminum on the other) in order to create a recess above the fan opening.
Stone repeated the procedure...
Stone repeated the procedure of slow hammering to create the 3/16-inch recess, using various styles of dollies for the various areas. The indentation serves a purpose besides looking good: It makes the surface more rigid.
Once he was satisfied with...
Once he was satisfied with the entire perimeter, he finished the area with the planishing hammer. The area was then sanded smooth.
At this point, the shroud...
At this point, the shroud is ready to do its job. There was still some metalwork to do to take it to the next level. The shroud was held with Cleco fasteners into a new clamping block (wood on one side, aluminum on the other) in order to create a recess above the fan opening.
Stone repeated the procedure...
Stone repeated the procedure of slow hammering to create the 3/16-inch recess, using various styles of dollies for the various areas. The indentation serves a purpose besides looking good: It makes the surface more rigid.
The plan was to fill the indented...
The plan was to fill the indented area with screen surrounded by a piece of metal trim. Stone used the aluminum template to trace the shape on a piece of perforated stainless screen.
The screen shape was cut out...
The screen shape was cut out with aviation snips …
… and test-fit into the indented...
… and test-fit into the indented area.
The trim surround for the...
The trim surround for the screen was created from a piece of 1/4x1/4-inch brass carefully bent into the shape of the shroud indentation. A couple pieces of tubing were tack-welded to the workbench. This single photo represents a few hours of heating, hammering, bending, test-fitting, and repeating the process—remembering that when the shroud gets painted and the brass trim piece gets chromed, the dimensions will change slightly.
When he got the shape perfect,...
When he got the shape perfect, Stone welded the two brass ends together to create a closed circumference. He has the most success welding brass by using low-heat silicone bronze welding rod.
Rounding the edges of the...
Rounding the edges of the brass was a challenge. Stone mounted the router below his workbench to round the sharp outer edges of the brass. He then sanded it to remove any hammer marks and other imperfections. It’ll get sanded again before it gets chromed.
After it was finished, the...
After it was finished, the brass trim was drilled and tapped for the fasteners.
After it was finished, the...
After it was finished, the brass trim was drilled and tapped for the fasteners.
Six studs—one at each corner...
Six studs—one at each corner plus one top center and one bottom center—hold the brass trim and the mesh screen to the shroud. The pointed studs were made to mark the mounting points in the shroud, so Stone will see where to drill.
Six studs—one at each corner...
Six studs—one at each corner plus one top center and one bottom center—hold the brass trim and the mesh screen to the shroud. The pointed studs were made to mark the mounting points in the shroud, so Stone will see where to drill.
Small mounts and lower gussets...
Small mounts and lower gussets were welded to the shroud to secure it to the radiator. With chrome and paint, it’s going to look great.