A major facelift was made on the 1966 Tempest that included more rounded bodylines with a Coke-bottle effect similar to the full-sized Pontiacs. New four-door pillarless hardtop sedans were added to the Tempest Custom line. Under the hood, the Chevy-derived 215 six was replaced by a new Pontiac-built 230 in³ overhead cam six, the only such engine found in an American production car at that time. This was also the first American-built engine to use a belt to time the camshaft to the crankshaft rather than a chain. The base OHC had a one-barrel carburetor and was rated at 165 hp (123 kW; 167 PS), designed for economy buyers. Optionally available as part of the Sprint option package on two-doors was a four-barrel, high-compression 207 hp (154 kW; 210 PS) version of the OHC six, marketed as an alternative to higher-priced European sport sedans, which had similar OHC engines. For those wanting V8 power, the 326 and 326 HO options continued with horsepower ratings of 250 and 285 hp (213 kW; 289 PS), respectively, and GTO engines stayed the same.
Source: Wikipedia (original)