o320-o360_decision_diagramDid you know that Vans Aircraft design three different lower cowls for the RV-8? There is one for the IO-360 installation; another for the common O-360 installation; and still one other for the O-320 installation. I suspect, back in 1995, the factory expected builders to use the less expensive smaller engines. However, sales numbers tell a very different story. While there is no easy way to to know the exact number, The Vans Aircraft support staff only knows of five in the last 5 years.

So, you are one of the few, the proud, the unapologetic who have a flying Vans Aircraft RV-8 with an O-320. Now lets assume you have decided you really want the greater power that comes from the O-360. You have a number of options. Let’s take a look at a decision tree diagram …

This diagram is a bit tongue-in-cheek but it brings up a few good points – the first of which is to ask if you really want to do this upgrade. The second purpose of the diagram is to highlight that there are a number questions to ask and answer before starting. Finally, if you have an RV-8 and it has an O-320 and it has the O-320 cowl and you are installing a carbureted O-360 and the plane is already painted then (1) you are in a very very exclusive club and (2) your should have your head examined and (3) the upgrade is possible but it will definitely not be in the original plans.

So, you are still game to do the upgrade?

OK, welcome to the club! Here is the magic piece of the puzzle, a custom fiberglass / carbon fiber airbox.


This airbox fits within the available space of an RV-8 O-320 lower cowl while attached to an O-360 MA-4-5 carburetor and fed from the existing cowl snout. The aribox uses the same air filter as called out in the RV-8 IO-360 installation.

The construction of this airbox will be covered in a separate post. However, as a teaser, I will say that Fusion 360 and a 3D printer were involved. By using CAD software and 3D printing technology, it was possible to reproduce this airbox with the critical tolerances. More important is the process can be accurately duplicated.

Initial testing of this airbox has yielded performance results which are more than satisfactory.