Ed Weaver:
I need my IO346 overhauled (IO346 overhaul shop). Any opinion on Mark Young at TropicAirpower’s work? From what I have seen on the forum and what I have heard – he is top notch. I don’t understand completely the difference between Zero Time Limits and a standard overhaul.
Technical Editor:
No one but the factory that made the engine can legally call an overhauled engine a zero-time engine, with a zero time logbook. You cannot represent an engine as zero-time, unless it came from the manufacturer with its new zero-time logbook. A new logbook from any other overhauler is just a new logbook; it does not create a zero-timed engine.
Note that this is the perfect time to segregate your engine and prop logs, if not already done. Most older planes have the prop log in the back of the engine log. It is better to have separate logs for them, for a number of reasons. You can photo-copy the existing prop log info (to attach it as original proof), and transfer existing prop log entries into the separate new prop log. That way if you should later have reason to sell the engine or prop separately, you will be able to get full value by having logs to go with them.
Overhaulers used to misuse the term to distinguish between a “dip-n-strip job”, and a proper overhaul. Disreputable shops would just clean everything, replace what was completely worn out, and reassemble the engine; even though it might still have parts/clearances that were halfway worn out. This kind of overhaul cannot reach another full TBO; it is simply a temporary repair job, even though it might meet the FAA’s requirements to classify it as an overhaul. A proper overhaul meets both the FAA’s definition AND the manufacturer’s definition, which requires the replacement of everything that is on the mandatory parts replacement list. It means that all internal clearances have been returned not just to within allowable service limits, but to the original new-engine clearances.
If done properly, an overhauled engine should have the same TBO expectation as a new one. But when it comes to shops other than Continental’s, they can give you a new logbook, but the engine time has to be continued. For example, you will then have two engine times that must be recorded. A year later you might have an engine that is 3,500 TTSN, and 100 SMOH (total time since new; and since major overhaul). If you get the zero time rebuilt engine from Continental, it would just be the 100 TTSN. The way the factories (Lyc and Cont) distinguished this was by calling a continued-time engine “overhauled”, while referring to the zero-timed engine as “rebuilt”. Both Lycoming and Continental offer new engines; rebuilt zero-timed engines (in which most parts are actually new); and overhauled continued-time engines. Any other shop can only offer continued-time engines, having different levels of quality depending on what they do and how they do it. I personally do not like anything but the best quality of overhaul. I consider anything less to be misleading, and to border on dishonesty when the plane is being referenced for sale with an SMOH time. Reputable shops will only do the top quality overhauls, with anything less being termed a “repair”, which does not confer overhauled status.
If you type ‘IO346 overhaul’ in the upper right search box on BAC, you will find info on this. Most shops no longer accept IO346 engines for overhaul. It is best to stick with the ones that have a reputation for doing them, as they are more likely to have accumulated some critical spare parts that have become scarce over the years. They will also best know where to look for anything they don’t have, and will have the needed data on this uncommon engine.