Thumpr 243/257 Hydraulic Flat Cam for Chevrolet Big Block 396-454. Street/strip, needs 9.5:1 compression, 2800+ stall, intake, Gears and headers, very rough idle. BBC 1965-66 396 c.i.d. models have an oiling groove in the rear journal. The listed part numbered cams will not fit these models, so if you require a Camshaft with the oiling groove, please call us and we will assist you with placing an order.