Dart 12100000 Cylinder Heads. 220 Race Series SBC Cylinder Head Standard Exhaust Bare Casting. Darts 220s are cast with extra thick walls to allow extensive porting and modification. These heads are ideal for serious street performance, bracket racing and restricted oval classes that require a stock type casting. The 220 is the ultimate in 23 degree small block cylinder heads. Premium alloy: Dart aluminum heads are cast from virgin 355. Aerospace alloy for superior strength and integrity. Shallow combustion chamber design improves combustion and allows use of larger valves for improved airflow. Interlocking ductile iron valve seats are compatible with stainless steel and titanium valves. Spark plugs are shifted toward…