The E-type and the 911 share the distinction as two of the most recognizable sports car shapes of all time. Both cars conceptually leapt ahead of the competition when introduced and both had teething troubles in their infancy.
But after eight years of production, the E-type had lost its edge and had become somewhat dated, while the 911 was just reaching the first of several pinnacles in its long history. Porsche's continual refining of the original 911 concept is precisely what makes the 2.2-liter and 2.4-liter such appealing cars today.
With the introduction of the 2.2-liter S in the 1970 model year and the 2.4-liter S in 1972, gone was Porsche's previous standard of attempting to extract the maximum horsepower per liter from its production engines. The 1969 2.0 S with 85 hp/L had the highest output for any normally aspirated standard production Porsche. These super peaky engines had to be revved mercilessly and were too noisy and tiresome for most drivers.
With 1970 and later 911s, Porsche strove to deliver maximum driving performance rather than maximum volumetric efficiency. For example, the 2.2 S achieved 82 hp/L and the 2.4 S, 81 hp/L. This transformation was completely successful and these last models of the true S (especially the 2.4 S) are considered the finest of the pre-SC production models. These are easy cars to live with on a daily basis, their performance is unequalled by many supercar contemporaries, they have comfort (ease of entry/exit) and they have a practicality and a robustness that is legendary.
As with the purchase of any thirty-year-old car, there is no substitute for a careful inspection by an expert. Porsche was not fully galvanizing the bodies in the '70s so look for signs of rust or poor repairs. The 901 gearbox of the 2.2s should be smooth, light and quiet. The 915 gearbox of the 2.4 and later cars tends to be notchy and often has balky synchros. A bit of transmission bearing whine is common but it can run like that for years.
The engines suffer fools gladly and truly love to rev. A puff of smoke on a cold start which clears up in a few seconds is common but not universal and seems to happen after long periods of storage.
Oil pressure should be at least 10 psi per 1,000 rpm with the oil warmed. Oil pressure can drop to near zero at idle depending on the type of dry sump lubrication system. The original Bosch mechanical fuel injection system is the best fuel system for the car even though many have had Webers fitted. The Bosch system works well and is very efficient if it isn't inactive for a long period of time.
Decent condition number 3 drivers can sometimes be found under $10K, but you will probably have to be quick to snag one at this price. At much under $10K you will probably be getting some sort of project. Over $15K should buy you a very nice driver. Over $20K and you are into the realm of low mileage, original cars or superb restorations. These cars are scarce and may take a lot of searching to find.
Make certain that if you are paying for an S that you are getting an S by checking all of the numbers carefully. Owning a good car will be an enlightening experience.