An Analysis of piston scuffing for Cadillac ATSL

Mod: Cadillac ATSL/LTG;
Changed items: Forged Pistons, Conrods, Bearings;
Case description:

Having been changed the piston kits, the ATSL had been idling for 5~6 hours. And the car owner drove it some 150KM away for a better run-in. But it came an abnormal noise. When it returned to the tuning centre (it ran in total 213km), the engine was disassembled, and was found 3 cylinders of its 4 were scuffed. The impacted areas which closed to the intake valves were scuffed seriously. But the elliptical of the skirt area were found with less damages. And the crowns were excessively burnt.

Analysis	Solutions
The run-in oil had been utilized over time	An engine shall not run over 160km with the run-in oils
Improper fuel	The improper fuel may release more heat, which may lead to over heat a cylinder that melts a piston
The shape of a cylinder might have been changed (not a standard round)	To ensure a cylinder’s shape is well maintained previously before installing a piston, otherwise, it needs to be bored
Overload	For the tuned engines, in high speeds, the pistons of which shall be redesigned; Like: enlarge their elliptical skirts, and Eccentric processing. But it might lead to an abnormal noise for the non-tuned engines.