If you’re racing in a class that requires you to run iron heads or are simply looking to build a bad ass sleeper motor these new CNC ported, 23-degree, cast iron pieces from RHS should fit your bill nicely. According to RHS these are the only CNC-ported 23-degree cast iron heads on the market for the small block Chevy. They are surely heavier than aluminum heads, but that don’t make ’em any less cool to us. 

Here’s the release from RHS:

RHS ®  Pro Elite ™  SBC 23-Degree CNC-Ported Iron Cylinder Heads

Airflow technology leader extends Pro Elite ™  series with new CNC-ported cylinder heads designed to maximize the performance of 360-434c.i. engines

Engineers at RHS ®  have recently designed the only Small Block Chevy 23-degree cast iron head for  360-434c.i.  engines  that  is  CNC-ported  from  the  factory.  The  precision  accuracy  and durability of the RHS ®  Pro Elite ™  SBC 23-Degree CNC-Ported Iron Cylinder Heads are derived not  only  from  the  CNC-porting  of  the  intake  and  exhaust  runners  but  the  CNC-ported combustion chamber, as well. 

The CNC-ported 240cc intake and 85cc exhaust runners optimize airflow volume and velocity while the 53cc combustion chambers are also CNC-machined to relieve the valve shrouding that occurs when the edge of a valve is in close proximity to the combustion chamber wall. Overall, the  full  CNC-porting  process  provides  more  consistent  runners  and  smoother  port-to-chamber transitions,  thereby  increasing  both  airflow  efficiency  and  horsepower.  In  addition,  these  new heads from RHS ®  are designed to use offset rockers in order to maximize the intake window at the pushrod opening for increased airflow.

As  with  the  rest  of  the  Pro  Elite ™   family,  these  SBC  iron  heads  come  with  a  host  of  unique features, including premium bronze valve guides and a multi-angle valve job. Also, ductile iron valve seats are inserted to better prevent seat and guide wear with alcohol and other racing fuel applications. The ductile iron 2.100″ multi-angle intake and 1.625″ radiused exhaust valve seats allow  for  superior  airflow  and  improved  atomization  with  racing  fuels.  In  addition,  the  heads feature a refined water jacket for more even water flow to reduce hot spots in the engine. For racing classes that mandate the use of cast iron cylinder heads, RHS ®  has designed the ultimate advantage by utilizing the latest in airflow technology.