The next most critical part of an air conditioning system in terms of providing optimum performance and trouble-free service is matching the compressor to the other system components.
The type of compressor most commonly used now in aftermarket systems is the axial type by Sanden (See our line of SANDEN COMPRESSORS). We do see a few engine swaps that retain the original General Motors/Frigidaire (DAG and R4), or the Ford Nippondenso compressors. And yes, a very few York/Tecumsehs are still on some restored classics. The Sanden compressor is a compact cylindrical unit about 8-1/2 inches long and about 5 inches in diameter. It is easy to spot with its barrel shape, aluminum color and small overall size. It has five or seven cylinders running lengthwise, thus the nameaxial compressor. Even though it is commonly refered to as a rotary, it is not. The Sandens are so popular because they operate smoothly, with a minimum amount of torque required to operate, because the load is distributed over multiple short-stroke cylinders. The Sanden compressor has another characteristic which we like, especially for street rods: its short stroke, low-displacement-per-cylinder configuration tends to make it less efficient at low RPM ranges (1200 and below), the same speed at which our engine-driven radiator fans are least efficient. This puts less heat load on the condenser and consequently on the radiator at idle speeds. On the average classic car requiring a smaller sized condenser, that is a blessing. Above 1200 RPM, efficiency rapidly increases; at operating speeds of 1800 to 2400 RPM it is about the most efficient pump on the market. It can be operated at continuous crank speeds of 6000 RPM. These characteristics make the Sanden an almost ideal performance compressor.
Displacement sizes for Sanden units are identified by the numbers on the label on the case. The numbering system is interpreted as follows: SD 508 = 5 cylinder/8.4 cubic inch, SD 7 = 7 cylinder/ 6.1 cubic inch.
Other Compressor Types: York
The York compressor was OEM equipment on most American cars in the fifties, sixties, and early seventies. The York is a rarity these days, but can be identified by its large square shape. The York compressor is much like a lawn mower engine, being a two cylinder, reciprocating pump. The reciprocating motion causes it to vibrate more than modern Sanden compressors. The York also has higher torque requirements for peak pumping, and they don’t like higher RPM operating speeds.
