QUESTION: Paul, I have a Lycoming 0-235C1B installed in a Piper Colt. What are your feelings about an STC to install either an 0-290 or 0-320 engine in this aircraft?
The 0-235 needs a top-end now, so I’m considering selling the engine as a core and installing one of the other engines.
ANSWER: Mark, there is no doubt that a top overhaul on an O-235-C1B is a costly venture. It’s the old “”supply and demand”" situation that tends to drive the cost of the rings and other components up in price. As you can imagine, folks who furnish parts for these older engines do not order in large quantities, therefore the price goes up for the entire food chain using those parts.
Assuming you understand that, it’ll give me a good starting place to answer the rest of your question. I recognize that economics becomes a very important part of any decision. There are a few things I’d like to mention that may add to those you need to consider before you come to a final decision. You’ll have to check the FAA website (FAA.gov) for any STCs that may be out there for installing the O-290 or O-320 series engine on your Piper Colt should you elect to go that way. If I were considering bypassing the top overhaul and installing a different engine, I’d look for an STC that would allow the installation of the O-320 series rather than the O-290 series. The reason I choose to go that way is that the O-290 series suffer the same predicament as the O-235-C series and that is parts are limited these days. Even though Lycoming is still continuing to support and build certain O-235 series, it hasn’t supported the O-290 series for many years. This is the driving factor that leads me to look at the 320 option since these are being produced every day by Lycoming. That in itself should let us rest easy with regard to parts availability for many years to come.
One other thing to keep in mind should you pursue the O-320 series: When you do your STC research, try to find one that uses an O-320 with a conical engine mount rather than a dynafocal type mount. This will not only make the swap easier, but will save you some money.
Mark, regardless of which way you go, the main thing is have fun doing it!
Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.