Home » Tony’s Tips » Articles » Heater Hookup Ports for Your B & C Series CumminsHeater Hookup Ports for Your B & C Series Cummins Cummins 330/370 5.9 Manifold Output 6CTA 8.3-“450 Diamond” Outlet 6CTA 8.3-“450 Diamond” Inlet Typical ‘T’ and mini-valve. They work great for heater outlets and inlets These mini valves are small, simple & reliable.Plus they come as a male by female pipethread which eliminates an extra fitting. Cummins 330/370 5.9-inlet or return to engine Above C series coolant return lines. Tee into either of these with a standard Brass Pipe Tee. The larger lower line will yield a higher flow.