CIS Injector BlocksTurboKraft's CIS Injector Blocks replace the stock plastic CIS fuel injector holders that are known to warp and crack especially when ported for more airflow. New phenolic insulator blocks are included to prevent heat soak from the cylinder heads into the injector bodies. Combined, they are a direct fit replacement for the stock plastic units. TK CIS Injector Blocks are CNC machined from billet 6061 T 6 aluminum alloy, and available in any bore size