Pontiac entered the horsepower race in 1956 with a dual 4-barrel carburetor version of the 316 cid engine. The following summary is an excerpt from "75 Years of Pontiac, The Official History" by John Gunnell.
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.
For additional information, see:
Pontiac Service Craftsman News - 1956 Pontiac service bulletin was first to publish technical details on this engine.
Rick Gonser Article - Article written by Rick about the 285 HP dual 4-barrel engine. Rick has this engine in his 1956 2-door sedan.
Batwing Air Cleaner Guide (with a Pontiac emphasis) (2.1MB) Article by Len Sokol on the unique dual 4-barrel air cleaner.
Dual quad Safari Article from "Pontiac The Performance Years Vol 2" on Len Sokol's dual 4-barrel '56 Safari.
Thanks to Rick Sorgen for the following documents.
News Release January 1956 News Release by Pontiac announcing the engine.
"The 1956 'NASCAR' Dual Four-barrel Engine" article by Len Sokol published Smoke Signals magazine. (Poor quality, Len send a better scan of this)
Motor Trend Article Article in July 1956 Motor Trend.
Engine / Suspension Parts List Parts list for the 285 HP car.
Rick Gonser's Engine ID Chart Parts list by Rick Gonser.
Carburetor Parts List Parts list for the carburetors.
Rick Sorgen's Notes Notes by Rick Sorgen on his research.
Picture of Ab Jenkins - 1956 World Speed Record (click on picture)