Just completed an annual and after all is back together front #5 (copilot foremost) is running quite cool. After a few minutes of run-up the others are too hot to touch but you can hold a palm against 5 indefinitely.
The annual involved some engine control adjustments, but would imagine any such would affect all cylinders equally (mostly).
Things checked:
- excellent compression
- good spark (new sparks too)
- valve springs strong
- Nozzle flow equal to other cylinder
- Mag check normal left to right and back
Any thoughts? Been two weeks of head scratching. Even called an IA with many many hours on these.