Timeserts are considered better. Should be able to thread with the head on the car. Use a strong vacuum at the thread site necked down with tubing to pinpoint the suction. Put grease on the threads of the tap to grab some of the swarf. You could open the exhaust valve on that cylinder and apply light air pressure with a shop vac exhaust or electric leaf blower to the tailpipe while tapping to blow chips out of the threads. Borescope the cylinder when done.

Good luck!!!

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer