Do top overhauls add value to your piston-engine airplane? This is a question I get a lot and the answer is almost always “No,” however a lot of owners/sellers don’t want to accept that answer, presumably because they’ve just spent thousands on engine work. “But I have new cylinders,” they say. “Isn’t that worth something?” Yes, it is, but you’re starting from the wrong baseline. You see, this type of engine work simply brings the value back to that of a fully functional engine and gives it marketability. In other words, if you didn’t do the top overhaul, the engine would be worth less and largely unsellable. Doing the “top” it does not add anything to the value of the engine.
“Why,” you ask?
The answer is simple. A top overhaul does not reset the engine TBO (Time Between Overhaul) interval. It is simply a stop-gap measure designed to do one of two things: 1) replace ailing cylinders in the hopes the engine will make it to TBO when a full overhaul will be needed or 2) to help an owner get more time out of an engine that is nearly timed out but still running well.
The rub, of course, is that you often don’t have the luxury of whether or not to do a top overhaul. That’s why it becomes very important to weigh the cost of a top overhaul against the cost of a complete engine overhaul. Depending on your engine and mechanic, a top overhaul can easily run three thousand dollars or more per cylinder. Have 6 cylinders that need replacing? Then it doesn’t take long to figure out that you could be throwing good money after bad if you’re getting close to your engine’s TBO. Have lots of hours left to TBO? Then it might make sense to do the top overhaul instead of blowing more cash on a full overhaul. For many engines, especially those that are turbocharged, a top overhaul near the mid-point of the engine life should be planned for. Without getting into the engine operating technique debate, suffice it to say that a mid-life top overhaul is a fact of life for many engines.
I too wish top overhauls added value. But alas, this is aviation and as with most things, there is rarely a positive return on investment (unless you factor in safety, peace-of-mind, joy of ownership, etc). Spending money doesn’t make you money but it can keep you from losing more money.
What do you think?