The dual-purpose road/race car that could be built from a kit of parts pretty much characterizes the early efforts by Colin Chapman and Lotus. The concept came more clearly into focus with the Six, but after more than 100 cars, the swing-axle front suspension became antiquated and the bodywork expensive to fabricate.
Compared to the Lotus Six, the Seven was a simplified, modernized and productionized club racer that set new standards in appearance and performance. Still roadable and sold in kit form to the enthusiast on a budget, the Seven introduced a generation of young enthusiasts to their first serious sports car that was also able to win races on the weekends.
The S1s were normally available with either the side-valve Ford 100E (1172 cc) or the BMC A Series (948 cc), though a few were fitted with Climax 1100s and called "Super" or "7C." With the Series 2, Chapman wanted to simplify the car, making it cheaper to build and even more affordable. The S1's alloy nose and fenders were changed to fiberglass and a few frame tubes were deleted.
Combined with an A-bracket to locate the rear axle (Colin found one part that could do the work of three), this made up the new Series 2. Probably the first Seven that was seen Stateside, it became a huge seller by Lotus standards. The new models were called the Seven America (BMC power), Seven and Super Seven; the last two being powered by the latest Ford engine (1000 cc, 1340 cc, 1500 cc or 1600 cc) with the Super getting a Cosworth cam and twin Weber carbs. The lighter chassis, more horsepower and Triumph rear axle made the Series 2 more trouble prone than a Series 1.
Today, it is common to see strengthened chassis and reinforced rear-axle casings even on unrestored cars. Though mechanically simple and reliable, all Sevens are lightly built. Parts breakage and outright disappearance of parts due to vibration are all part of the Seven experience. Though it was one of the quickest small-bore cars on the road for decades, its stiff springing, lack of creature comforts and aging enthusiast base has caused them to lose some appeal.
To rescue the situation, companies like Caterham and Westfield build updated versions of the Seven, with longer cockpits and kidney-friendly springing. Remarkably, prices for the new cars are higher than the value of some originals, showing the appeal of the idea of the Seven versus the appeal of actually owning and driving an original car. Today, they are weekend cars for smooth roads or ultra-competitive vintage racers. That's pretty much where they began and probably where they belong.
As for value, nicely done Sevens, with all the right upgrades, will continue to trade in the $18,000-$25,000 range for the foreseeable future.