These reasonably priced AFR 210cc intake port small block Chevy angle plug cylinder heads are available in three stages of performance. The Race Ready version features 100% CNC ported intakes while the higher flowing Competition version features 100% CNC ported intakes with greater detail. Both come with 100% CNC ported combustion chambers and 80cc exhaust ports with a 3/4î thick head deck (ideal for nitrous or blower applications). Standard valves are 2.080 intake and 1.600 exhaust with AFRÍs hardened ductile iron interlocking valve seats. The exceptional flow characteristics, 23_ valve angle, and standard valve spacing make this the perfect aluminum cylinder head for 350 to 400 cid engines in bracket drag cars, sportsman oval trackers, and highly modified street class cars operating between 3000 and 7500 rpm (higher rpm ranges possible depending on combination of parts).The 210cc cylinder heads are available in either standard or spread port exhaust. Straight plug versions and down nozzle provisions are special order only. No special parts are required. Dual valve cover bolt pattern is standard. Exhaust port is raised .250 over GM L98 cylinder heads. Note: These cylinder heads are specifically design for 1992-95 Corvettes and 1993-97 Camaros LT-1 and LT-4 engines using the GM LT-4 or equivalent manifold. Chevrolet LT4 - 210cc Competition CNC Strip Porting - 55cc-65cc Combustion Chambers, LT4 Plug - Bare Heads