Turbo-Jet

what are the most common sizes found on an engine? i want to buy some bottoming taps to chase threads.

1/4-20
5/16-18
3/8-16
7/16-14

fine pitch ever used?

norvalwilhelm

Fine are not normally used and the only place I can think of is the rocker studs and the carb studs.

MikeC

Fine threads are used to bolt the flywheel to the crank, but in most cases would not required chasing the threads.

Gordonm

Just used one last night for the ring gear. 3/8-24. Not many going to go in there but I try to clean out all threads before reassembling anything. The torque figure is going to be more accurate and assembly is easier. Also the bolt in the front of the crank is fine thread for holding the balancer on