Rules and regulations are generally a good thing in motorsports. They mandate a certain level of safety and can keep the races interesting, since competing vehicles must have similar styles and engines. But if you want proof that keeping the rulebook short and sweet breeds excitement and innovation, just take a look at Can-Am Racing.

In the late 1960s and early 1970s, the Canadian-American Challenge Cup thrilled spectators with an anything-goes attitude to racing cars. There were no restrictions on vehicle weight or engine size. Superchargers and turbochargers were fair game. So were oversized rear spoilers and even engines pulled from snowmobiles. The result was a group of hugely fast and diverse machines, driven with impunity to record-breaking lap times.

The glory days were short-lived. The death of driver Bruce McLaren in 1970, increased costs, and the need for rules to monitor safety and fuel economy drove away public interest. Freedom to innovate within the league subsided and interest dwindled. The racing series ended in 1974. It was briefly brought back a few years later, but the spark was gone.

The official competition may be dead, but you can still see Can-Am cars on the track. Every August at the Monterey Historics event in California, carefully preserved cars from this league are dusted off, fueled up and driven hard, all for the thrill of watching people drive like lunatics. As Mazda Raceway at Laguna Seca prepares to host the races this weekend, here's a look at the cars that best demonstrate the brilliance of this extinct racing league.

1965-1966 Lola T70 Mk2 Spyder: The winner of the first ever Can-Am championship was this mid-engined convertible from Kent, England. If the names of drivers like Bob Bondurant and Jackie Stewart sound familiar, it’s partly because they had podium finishes while piloting this exceptional race car, which beat rivals like McLaren and Chaparral. Weighing in at just 1,800 pounds, its power came from a mid-mounted 5.7-liter Chevrolet motor producing about 500 horsepower.

1966 Chaparral 2E: Chaparral was run by eccentric Texas oil tycoon Jim Hall, and the company spawned some of the most bizarre automobiles to ever race. Built between 1963 and 1970, these mid-engined models were the first vehicles to add body kits and, more importantly, rear wings to take advantage of aerodynamics for better handling. The 1966 2E was designed from the outset to harness downforce for added grip during crucial turns. Its comically large rear wing sat more than four feet above the rear end of the car and could produce 240 pounds of rear downforce at 100 mph. Within two years, the idea of feeding the weight of aerodynamic downforce to the rear uprights had been adopted in F1.

1969 McLaren M8B: That distinctive orange paint you’ve seen on the McLaren F1 LM and P1? It comes from the racing livery for this car. Another car that used an enormous wing for downforce, the M8B won six races for McLaren in the 1969 season and gained driver Bruce McLaren and his team a reputation as one of the top contenders on this circuit. The wing was mounted directly to the rear wheels’ uprights. That sent the downforce straight to the wheels instead of through the chassis, leaving the suspension open to handle bumps. In 1970, Bruce McLaren died after crashing the M8D, a successor to the M8B.

1970 Chaparral 2J: This contender for the craziest vehicle ever set on four wheels looks like a knocked over refrigerator. That big hump in the back? An embedded snowmobile engine that sucked the ground underneath. Weighing just 1,810 pounds and propelled by a 650-horsepower engine, the 2J had so much power and so much grip that it dominated the circuits. It only lasted one season before being banned for the unfair advantage posed by its adjustable aerodynamics.

A Porsche 917-30 receives an engine swap in the pit. Mazda Raceway Laguna Seca Archive

1973 Porsche 917-30: The 917 won the 24 Hours of Le Mans for Porsche a few years prior, and this 1973 version was among the last entrants for the brand in Can-Am racing. Its 12-cylinder motor was good for up to 1,100 brake horsepower. Porsche withdrew from Can-Am after the 1973 season, but they took the car for a lap at Talladega in 1975. There, it hit 240 mph in the straightaway, a speed that's still impressive today.

__1974 Shadow DN4:__In the final year of the original Can-Am series, cars were required to hit at least 3 miles per gallon, which meant the previous years’ 1,000-plus horsepower monsters were out of the running. The Shadow DN4 ran on an 800-hp, 495-cubic inch Chevy V8, which met the regulations and took drivers Jackie Oliver and George Follmer to first and second place in the 1974 season. Can-Am’s glory was already fading, and the Shadow DN4 was the last vestige of the glory years of the series.