Fits 5F8265 Precombustion Chamber Assembly Fits Caterpillar D375 D386 D397One New Aftermarket Replacement Precombustion Chamber Assembly Fits Caterpillar (Fits CAT) D Series Engines This aftermarket replacement precombustion chamber assembly Fits Caterpillar (Fits CAT) D375, D386, and D397 industrial and marine diesel engines. The precombustion chamber is a critical engine component seated in the cylinder head where fuel ignition and initial combustion begin. Over time, precombustion chambers can rust through from the water