In March 1956, an “extra hp” V-8 was released. It also displaced 317 cubic inches, but came with 10.0:1 compression heads; dual four-barrel Rochester carburetors; a special intake manifold; a fuel pump with larger valves; a dual-element Delta-Wing air cleaner; a greater overlap high-output camshaft; revised valve timing; longer-stemmed valves; high-tension valve springs and shields; anti-pump-up hydraulic lifters; and modified electrics. The output of this so-called “NASCAR” engine was 285 hp at 5100 rpm. It was tested for 0-to-60 mph in 11 seconds flat and 16.2 mpg fuel economy. Pontiac experts estimate that 200 cars were equipped with this motor, which was intended primarily for professional stock cars, but found its way into amateur drag racing cars.

 The potential of the 285 hp engine was not lost on 73- year-old speed ace Ab Jenkins. who took a high-output Chieftain 860 coupe to the Bonneville Salt Flats for a 24- hour world speed record run in which he covered 2,841 miles at an average speed of 118.37 mph. The same car, with drilled-out wheels to make it lighter, then set a 100- mph distance/speed record  of 126.02 mph.