3978374CN Cummins Heat Exchanger, 5" Diameter x 27" long. Copper Nickel core Replacement for Cummins part #3978374. Raw Water Inlet/Outlet 1.75". We only sell this part with a copper nickel bundle. Used on the following engines: SD4.5 CM2150,B5.9 LPG Plus CM556,G5.9,ISB 5.9 G CM2180,B4.5s,ISF3.8 CM2220 AN,ISB6.7 CM2250,B4.5 RGT,ISB CM800,QSB5.9-44 CM550,B5.9 G,G3.9,ISBe4 CM850,ISD6.7 CM2150,ISD6.7 CM2150 SN,QSB6.7 CM2250,QSB3.9-30 CM550,QSB5.9-30 CM550,B Gas Plus CM556,B6.7s,ISB CM2150,ISD4.5 CM2150 SN,ISB CM850,B LPG Plus CM556,B4.5,B3.9,ISF2.8 CM2220 AN,ISB6.7 CM2150 SN,QSB6.7 CM850,ISBe4 CM2150,G5.9 CM558,ISB6.7 CM2150 SQ,ISB4.5 CM2150 SN,ISB CM550,QSB5.9 CM850,B Gas International CM556,QSB4.5-30 CM550,ISBe CM800,ISBe5 CM2150 SN,QSB4.5 CM850,B5.9,ISBe CM850