The Classic Car Era started after World War II when a surplus of supplies and manpower, a newfound freedom, a strong economy and good roads, caused consumers to demand bigger and more powerful vehicles. Up until the 1970's gasoline in the United States was so abundant and cheap that many vehicle manufacturers had little regard for fuel economy so more horsepower was simply a matter of building bigger engines. However the resulting pollution that produced dense smog in several major cities was a concern and the Environmental Protection Agency (EPA) determined that much of it was caused by unburned gasoline vapors from vehicles. The United States Congress enacted the Clean Air Act in 1973 to force states to in turn force manufacturers to fix the problem.
The Clean Air Act was established after years of research into the types and causes of air pollution and initially addressed the most obvious causes, particle pollution, which amounted to ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide and lead. It directed each state to adopt new laws to reduce the pollutants but most of the problem fell on the shoulders of manufactures who were forced to meet new emission standards. And some states established requirements for annual inspections which led to an industry of aftermarket devices.
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The primary goal was to reduce unburnt fuel and crankcase emissions. There was a lot of trial and error in the early years but three devices stood out as successful. One success was the positive crankcase ventilation (PCV) valve which did a great job of preventing crankcase vapors from venting to the atmosphere but it also inhibited the engine's ability to breath freely, which reduced horsepower, and resulted in more sludge buildup in the lubricating system. Another success was the catalytic converters which absorbed unburnt gasoline before it left the tailpipe. But they were expensive and easily ruined by too much gasoline. And then there was the all new electronic ignition systems which replaced the mechanical ignition points and spark advance systems with a computer that could do the job more efficiently. However initially they were had problems and mechanics were very slow to accept them because they were expensive and not adjustable.
Vehicle manufacturers soon learned that reducing engine emissions would invariably result in the loss of horsepower and neither they nor consumers were happy about that. Spending more money for a vehicle with pollution control devices was one thing but to then lose performance was unacceptable so manufacturers tried to compensate by making vehicles smaller and lighter.
Then in October of 1973 the Organization of Arab Petroleum Exporting Countries (OAPEC), which included the nations of Egypt, Syria and Tunisia, enacted an embargo against the United States and other NATO nations and the Clean Air Act issues became less important. The problem was started by our support for Israel to expand into the Golan Heights over the objection of their neighbor Syria. Politicians assumed that OAPEC needed our business as much as we needed their oil and would therefore not go through with the embargo, but they did and by December of 1973 we were cut off. The embargo caused a big stir among the NATO nations, many of which threatened to drop out unless the U.S. quit supporting Israel. The U.S. was negotiating with other countries for oil supplies the following March when OAPEC ended the embargo due to a new Israel and Syria peace accord.
The Classic Car Era was a time of consumer greed - "We want more power, more performance, more accessories" - and what followed was a time of austerity. The combination of the Clean Air Act and the oil embargo was a wakeup call to the nation and the automobile manufacturers in particular. The obvious solution to both events was to improve fuel economy and reduce horsepower. Mid-sized classic cars like the Dodge Dart, Ford Falcon and Chevy II that were so much fun with big V8 engines were given six and four cylinder engines to meet the new standards. And European and Japanese automakers began to import compact cars like the Toyota Corolla and Volkswagen; leading us to the Modern Car Era.