For the open shell van der Waals molecule, CAr, the potential energy curves (PECs) for the B (3)Pi and 1 (5)Sigma(-) states, the B (3)Pi-1 (5)Sigma(-) spin-orbit coupling and the B (3)Pi fine structure splitting are determined using multireference configuration interaction wave functions as large as similar to 8 million configuration state functions. The B (3)Pi state is strongly bound, with D-e=5100 cm(-1). R-e(B (3)Pi)=3.7a(0) and is considerably shorter than R-e(X (3)Sigma(-))=6.07 a(0). The PEC for the repulsive 1 (5)Sigma(-) state crosses that of the B (3)Pi state at R-x(1 (5)Sigma(-),B (3)Pi)=3.31a(0) leading to spin-orbit induced predissociation. The B (3)Pi-1 (5)Sigma(-) spin-orbit coupling is the result of valence-Ryberg mixing in the B (3)Pi state and is considerably enhanced by the heavy atom effect. The heavy atom effect is also reflected in a marked decrease in the fine structure splitting of the B (3)Pi state with increasing vibrational level. The implications of these results for using CAr(B (3)Pi) in laser induced fluorescence detection of CAr(X (3)Sigma(-),v) are discussed.