Diesel Engine Emission Reduction Technologies like Ducted Fuel Injection and Cooled Spray use passive hardware elements near the fuel injector spray holes to improve combustion and reduce particulate matter, with minimal impact on other performance parameters. This paper discusses the fabrication, installation and testing of Cooled spray inserts in a heavy-duty diesel engine. A cylinder head assembly with a Cooled Spray insert design, developed by Wabtec, allows use of multiple insert geometries for test purposes. As there are multiple test geometries planned and because proper alignment of the insert and injector is critical for the combustion process, manual alignment of the Cooled Spray device to the fuel injector is required. The location of injector holes within the cooled spray insert are imaged using a fiber-optic borescope. Imaging of the alignment with different injectors shows varying degrees of alignment success, suggesting that the injector nozzle variation may contribute to the misalignment between the individual nozzle holes and the fuel passages of the insert. Prior to the engine testing, a one-dimensional thermodynamic engine model provided boundary conditions for single cylinder engine testing. Finally, engine performance of the cooled spray insert is compared to the baseline engine performance. The test results show that an alignment improvement of 0.15mm reduced Filter Smoke Number by 85%. Additionally, Cooled Spray caused 70% reduction in Filter Smoke Number compared to the non-Cooled Spray for one condition while showing emissions parity or increases at other conditions.