Should I switch engines on my Super Sport?

Q: I am currently flying my Wag Aero Super Sport (essentially a short-wing Cub) with a Lycoming O-290-D2 engine. It is coming due for a major overhaul (by age, not hours.) 

It appears that it is increasingly hard to get parts for this engine, so I have begun to consider replacing it with one that is currently supported by Lycoming. The O-320 is suggested, but there are many of them.

Is there an O-320 that would fit on my existing engine mount and within my existing cowling?

James Beeghly

A: James, I’d like to know the answers to a few questions before I get started on my answer to your inquiry. I’d like to know how many hours you fly this aircraft per year and what your age is.

Now, I suppose you think I’ve gone off the rails, but I’m trying to let logic creep into helping you make your decision.

It’s important to know the condition of your present O-290-D2 engine. What is the oil consumption, how are the hot differential compression checks when taken at normal engine operating temperatures, and the overall operation of the engine?

Without really knowing the history of your engine, I think the answer to these questions may help us determine which way to approach what needs to be done going forward.

If the engine does not have any serious issues, then why not continue to keep it in service?

With an aircraft like yours and with that engine, if all is working well, why kick a sleeping dog? You and your maintenance folks know the health of your engine, so I’d let that engine health be the determining factor.

If oil consumption or engine temperatures are a problem, then the choice may have already been made for you.

There is no doubt that parts for the O-290-D2 engine are becoming rather scarce. That also leads to higher parts prices for any of those used serviceable parts, as you can imagine.

I honestly wouldn’t know where to tell you to even begin to source out parts for your engine. This is something that you may want to do a little research on just to see what’s out there.

Moving to a Lycoming O-320 series engine is doable with some cautions.

My suggestions would be to contact other Super Sport owners before getting too excited about making that move.

There may be one major stumbling block when going to the O-320 series engine: You have a conical engine mount, which limits you to which specific models of Lycoming engines you might choose.

Realistically speaking, you are almost limited to the Lycoming O-320-A series engines because they are all conical mount engines. There are some other 320 series that have conical mounts, but they are rather rare and difficult to find in the marketplace.

The other models of the O-320 that are commonplace in the later production Piper and Cessna aircraft have moved to the dynafocal type engine mount. Of course, that would require you to purchase a completely new engine mount.

Again, possibly some other owners of this aircraft have already encountered the same situation and have found other options. If you can get them to share their options, that might make it easier for you to figure out your next steps.

Talking to other Super Sport owners would also be a good source of information regarding any cowling changes.

One good thing about stepping up to an O-320 series engine is the fact that they are rated at 150 horsepower @ 2700 RPM versus your 140 hp @ 2800 RPM. 

If you are looking for a run-out O-320-A series engine, be very careful because, first of all, they are difficult to find. Secondly, if you locate one, I’d caution you to review the complete engine logbook closely to make certain it’s got a good clean maintenance history.

I can tell you I’ve heard plenty of stories about the “great deal” someone got on a used, run-out engine that cost them more to make it airworthy than they would have spent on a factory engine.