At 3.875-inches, the 350 has one of the smallest bore diameters in the Pontiac engine family. Only the '55 287 (3.750) and '63-'67 326 (3.719) are smaller. Though the stroker crank gains the real inches, a 0.030 clean-up was performed. The pen points to factory-issue valve relief chamfers atop the 350's bores. On this 1973 casting, the chamfers are adjacent to the exhaust valves only. Later 350 block castings have them facing both valves. These chamfers help unshroud the valve heads for improved breathing, but also add combustion chamber volume for reduced compression ratio. A little known fact is that camshaft lifts over 0.650-inch will send the valve heads smashing into the bores on 287, 326 and 350 blocks, unless radical chamfering is performed. Our 0.549/0.573 lift hydraulic roller will be safe, however.