Aren't some rocket engines being produced by 3D printing? If a rocket engine can withstand high temperatures, then so can an auto engine.
Decades ago, I had a car that had overheating problems. 20 years ago, I rebuilt the engine. I found that the engine block and cylinder head had lots of imperfections in the water jackets, and casting debris within. Same for the air intakes of the cylinder head. I carefully removed the casting debris and ground down imperfections. After assembling the engine it ran beautifully, very cool and with much more horsepower. Still runs great today.
3D printing is superior in many respects than traditional casting of engines. Pathways can be smoother and more efficient.
The revised V6 Chrysler began using in 2018 JL Series Jeep have had such problems... Mexico.