2011 Road Tour ’55 Chevy – Vintage Air Install
by Ed Kimball
Air Apparent – What it takes to keep your cool
By Ron Ceridono
Speaking for those who have driven cross country in a street rod with the windows down and the vent windows flipped out because the incoming 110-degree air was still cooler than any of the interior surfaces of the car, or traveled in a snow storm wrapped in a blanket driving with one hand on the steering wheel and an ice scraper to clean off the inside of the windows in the other, we’ve come to believe a climate control system is one of the most important parts of any build. And for the kind of miles our Road Tour cars rack up, it’s a necessity.
As in the past, this year’s AMSOIL/STREET RODDER Road Tour ’55 Chevy was equipped with a Vintage Air heat and cool unit installed by the car’s builder, Woody’s Hot Rodz. But rather than look at the specific installation we’re going to concentrate on how these heat and A/C units work in general, and what all the parts do.
The heater portion of a heat and cool unit seems simple enough—hot water from the engine circulates through a small radiator called a heater core, a fan blows air through the core, and you stay warm. However, like most things, the heater function isn’t as simple as it looks. In today’s sophisticated systems warm air may be directed to defroster outlets, or blended with cool air to produce the desired outlet temperature. That means the doors that control airflow through the heater core and A/C coils have to be operated precisely, which means electronics for optimum results. In addition, an electrically operated valve regulates water flow through the heater core rather than the simple on/off variety.
On the cool side, the process is slightly more complicated, but the easiest way to understand it is this: An A/C unit removes heat—the air coming out of the vents is cool because the heat has been absorbed by the refrigerant, taken outside the passenger compartment, and dissipated.
There are seven basic components in an air conditioning system: compressor, compressor bracket, evaporator (inside car unit), condenser (outside heat exchanger), hoses and fittings, the drier, and a safety switch.
Here’s how they all work: The heart of the system is the compressor that pumps refrigerant. In operation, the refrigerant evaporates to a gas and absorbs heat as the warm air is blown over the evaporator coil inside the vehicle. That gas, in what is referred to as the low (or suction) side, is pulled into the compressor, then pushed through the condenser where air flowing through it carries off the heat. As the heat is removed, the refrigerant condenses into a high-pressure liquid that is poured into the receiver/drier. Pure liquid refrigerant on the high side then flows though the expansion valve, which has a variable orifice that meters the refrigerant according to the demands of the evaporator—when warm, the orifice is largest and it gets smaller as the evaporator gets colder. As the atomized refrigerant sprays into the larger opening of the evaporator and liquid droplets begin to pick up heat, the refrigerant evaporates to a gas, which then returns to the compressor to start the cycle all over again.
It’s important to think about the air conditioning in your vehicle as a system; consequently all of the components must be sized properly and matched.
The major factor in selecting a system is the size of the area to be cooled. Basically the larger the vehicle, the more cooling capacity is required and the larger the evaporator will have to be. Vintage Air recommends using the largest capacity evaporator that will fit in the vehicle. After all, you can turn down the fan and adjust the temperature on a system if it gets too cool inside the car, but you can’t turn up a unit that is maxed out if it’s too small to cool a large area.
As the condenser dissipates the heat to the air, Vintage Air recommends selecting the largest condenser that will fit within the dimensions of the radiator core.
A general rule for surface area for an R-12 system is a minimum of 210 square inches on a two-row, 5/16-inch copper tube and aluminum fin condenser. This is a general rule; it is not absolute, but it is a place to start. HFC-134a requires about 20 percent more capacity, which means with a conventional tube and fin condenser you need about 20 percent more size. Our Super Flow condensers give that increase in capacity without additional size. By using flat tubes manifolded together so that the refrigerant flows through multiple tubes each pass, we get virtually 100 percent contact of the refrigerant with the condenser tube walls. This design also offers very low restriction in the pathway through the condenser and is up to 40 percent more efficient than a comparable sized copper tube and fin-type condenser.
Cooling System Considerations
When designing a cooling system for any car the same theory that applies to A/C can be applied to radiators—too big is never a problem, too small is. To prevent heating problems with the A/C on or off, our ’55 is equipped with a U.S. Radiator cross flow conversion with dual 11-inch fans.
Insulation and Weatherstripping
According to the experts at Vintage Air, the single most important factor in improving the efficiency of a climate control system is how well the vehicle is sealed and insulated. As an air conditioner operates by removing heat, the less heat there is to remove the more effective the A/C will be. Tinted windows help reflect the heat soak from the sun, and this helps the air conditioner cool the vehicle more efficiently as well. And it goes without saying that good weatherstripping and door/glass seals also will help isolate the interior and lessen the load on the A/C system. To that end all the weatherstripping in our Road Tour ’55 was replaced with new rubber from Steele Rubber Products.
Along with new rubber seals the two-door body was given a liberal dose of Dynamat for its acoustic and thermal insulation properties. For additional insulation Dynaliner can be applied over Dynamat.
While A/C may not add a huge load to the electrical system by itself, when the blower motor is on high and additional engine cooling fans are at work the load on the electrical system can grow, often requiring more output than the average alternator can supply, especially at low engine speeds. For that reason a 100-amp or larger alternator is normally required. Of course when a variety of electrical accessories are included and a high-amp alternator is used the electrical system has to be up to the task as well. The main charge wire has to be of sufficient gauge and of course it makes life easy if feeds are provided for all the accessories requiring power. For all those reasons, plus ease of installation and peace of mind, Woody’s used a Painless Performance wiring harness. A contemporary climate control system is a great addition to any street rod. Choose the right unit, make sure the cooling and electrical systems are adequate, and don’t forget weatherstripping and insulation and you’ll stay warm and keep your cool.
The AMSOIL/STREET RODDER Road Tour ’55 was equipped with a Vintage Air Gen IV SureFit System that features: fully electronic fly-by-wire controls, high-capacity aluminum plate fin cooling coil, copper/brass Cuprobraze parallel flow heater coil, molded high-volume center plenum vent design, optional four-duct plenum available, complete “just right temperature” air blending, high-capacity dehumidified defrost volume, and smooth steel firewall cover panel.
Steele Rubber Products
Woody’s Hot Rodz