Many hot rodders don't think about cooling until every other part of their project is finished. Choosing a radiator and fan may not be as much fun as choosing an engine, paint, or wheels, but waiting until everything else is done and then trying to find a radiator and fan that'll fit is not the way to keep a hot rod cool.
Think back to all the rods you've seen on the side of the road or pulling out of line at the entrance to a car show, sweet-smelling steam blasting from the radiator and a tell-tale green trail running down the pavement. Don't let that be your street rod. We certainly don't want that to be Project Shop Truck when it hits the road.
As you know from recent articles, Project Shop Truck is STREET RODDER's stab at building a custom '47 Chevy truck completely from aftermarket parts. We're counting on it to be a reliable cruiser and getting the cooling system right is a critical part of achieving that. Besides that, the truck's going to have the STREET RODDER name painted all over it and it wouldn't be good PR to have our rolling billboard parked in a puddle of its own chartreuse juice.
Creating the radius holes for the fans took seconds on the adjustable sheetmetal hole cutter.
The first key to running cool is to move water. That means selecting a radiator that will drop the coolant temperature sufficiently. Our choice was one of U.S. Radiator's new Tripleflow radiators. The Tripleflow has walls inside the core that route water through the radiator three times instead of one. Don Armstrong at U.S. Radiator explained that this technology isn't new, but has been used for years in Midget and Sprint Car racing.
Did you notice that the inlet on our radiator (PN 80071) is located on the left side? Water is fed down the left side, then back up the center, and down the right side before hitting the outlet, effectively tripling the surface area and, according to Armstrong's testing, reducing outlet water temperature an average of 15 percent over single-pass radiators. The second key to running cool is moving air. Without air moving through the radiator, the outgoing water isn't going to be much cooler than the water going in-no matter how much surface area you give it.
At highway speeds, the motion of your car forces air through the radiator, but when stuck in traffic or idling in line at that car show, you need a reliable fan to keep cool. For Project Shop Truck, we could have chosen a mechanical fan, driven by the engine, but decided on an electric fan. One reason is dependability under slow-speed conditions, when engine rpm is low and air isn't being forced through the radiator by the motion of the car.
Another reason is that a compact electric fan would fit in the limited space of the '47 Chevy's engine compartment. That was our theory anyway. We'll get to that.
With the fans in position, Sebastian marked the positions of the mounting holes...
We ordered a 17-inch High Output Single RAD fan kit (PN 16217) from Derale Performance. Derale has tested this fan to move up to 2,400 cfm. Armstrong got a reading of 320 linear feet per minute using a handheld airflow meter. In either case-plenty of air for Project Shop Truck.
This Derale fan features a symmetrical housing so that it can be mounted on either side of the radiator for use as a pusher fan or puller fan. We mounted it on the rear of the radiator as a puller, which is more efficient. Pusher fans have the disadvantage of physically obstructing airflow to the radiator, and pushed air is more likely to bounce against the radiator causing turbulence.
Getting the most advantage of a puller fan requires a shroud between the fan and the radiator. Since the whole purpose of the fan is to draw as much air as possible through as much of the core as possible, we chose the largest diameter that would fit. But without a shroud, even our 17-inch-diameter round fan would miss a lot of potential air from the four corners of the 20-3/4x19-3/4-inch radiator, so we had U.S. Radiator create an aluminum shroud before shipping the fan and radiator to Hot Rods by Dean in Phoenix, where they were waiting to install it in the Chevy.
... then finished the job at the hole punch.
