HISTORY: 265 / 4.3

[] 265 / 4.3L

3.736 in Bore

3.00 in Stroke

265 CID 1955-1957

  The 265 cu in (4.3 L) V8 was the first Chevrolet small block. Designed by Ed Cole's group at Chevrolet to provide a more powerful engine for the 1955 Corvette than the model's original "stovebolt" in-line six, the 165 hp 2-barrel debut version went from drawings to production in just 15 weeks.

 Cole's design borrowed the valve train being used at the time in the Pontiac V-8 for 1955. The stud mounted independent ball rocker arm design patented by Pontiac engineer Clayton Leach was first used in Pontiac's new V-8 in 1948. GM forced Pontiac division to share its valve train design in Chevrolet's new 265 V-8 in 1955.

 A pushrod engine with hydraulic lifters, the small block was available with an optional four-barrel Rochester carburetor, increasing engine output to 195 hp. The oversquare 3.75 in, bore, 3 in. stroke engine's. The 4.4 in. bore spacing would continue in use for decades.

 Also available in the Bel Air sedan, the basic passenger car version produced 162 hp with a two-barrel carburetor. Upgraded to a four-barrel Rochester, dual exhaust "Power Pack" version, the engine was conservatively rated at 180 hp.

 A shortcoming of the 1955 265 was its lack of any provision for oil filtration built into the block, instead relying on an add-on filter mounted on the thermostat housing, and that was an "option only". In spite of its novel green sand foundry construction, the '55 block's lack of adequate oil filtration leaves it typically only desirable to period collectors.

 The 1956 Corvette introduced three versions of this engine – 210 hp with a single 4-barrel carburetor, 225 hp with twin 4-barrels, and 240 hp with two four-barrel carburetors and a high-lift camshaft.

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