GM casting number 340292 represents the legendary small-block Chevy (SBC) "Turbo" cylinder heads. Introduced in the 1970s and sold exclusively over the counter as high-performance race parts, these sought-after cast-iron heads feature 64cc combustion chambers, angle spark plugs, and large 2.02"/1.60" valves. Today, they are prized by drag racers and hot rodders doing period-correct restorations or maximizing naturally aspirated small-block performance.