Modified Engine Noise After Nozzle Replacement (Experience on AFN) (Articles)

If the VP 37 engine sounds different after replacing the injectors (e.g., harsher, metallic ticking on cylinder 1 or multiple cylinders, etc.), a changed installation position of the injectors may be the cause.

Despite the relatively tight fit in the cylinder head and the clamping claw, the nozzles can each be rotated and tilted in all directions by a few degrees.
When tightening the retaining screws, they may be fixed at an uneven angle, which can noticeably change the engine noise.

If the nozzles are fixed as precisely as possible in the exact center of all the spaces, there is a good chance that the engine will run smoothly.