The timeline for an overhaul (once at the shop) varies from 3-8 weeks or sooner if your shop has an engine ready to exchange for yours. In most cases the timeline is so long because there’s only a few shops in the country that overhaul cranks and cases and it’s their timeline that primarily sets the schedule.
You’ll also have some down time removing and reinstalling the engine and possibly a few extra days for shipping too. There are sometimes unforeseen circumstances that can delay your engines. The two most common delays outside the shops control are: 1) Delay getting new parts – most of the time this is cylinders. and 2) Delays at the case and crank shops. They get backed up during random surges of work and at the end of the year. Sometimes these situations can delay you as much as a month or so.
One last note – Double check your timeline with the shop right before shipping. Things change so quickly and within a few days time, the shop could have received a pile of work. Don’t assume that his estimate from 90 days ago will still hold up.
If downtime is a major issue for you, contact me at (317) 550-0030 and I’ll find a shop that can prepare an exchange engine for you ahead of time. This way, your new engine can be sitting next to your airplane when it’s time to pull the old off.