I’ve been researching how to have my cake and eat it, too. How can I build an RV-8 that is plush but also accepts a parachute that has modern & redundant systems but is also lightweight? I’ve been looking for places to shave some weight here and there in my build.

The IO-390 is the most powerful engine the RV-8 can accept, but it also weighs a lot more and is only available from Lycoming as it’s not sold in kit form for other companies to assemble. The most common engine used in the RV-8 is an IO-360 or its carburated cousin, the O-360. As I am building an aerobatic RV-8, I need fuel injection, so I’m discounting the carbonated versions as considerations.

O-360-A1A	180 HP	285 lbs (parallel)
O-360-A4M	180 HP	285 lbs (parallel)
IO-360-M1B	180 HP	290 lbs (parallel)
IO-360-A1B6	200 HP	325 lbs (angle)
IO-390-A3B6	210 HP	315 lbs (angle)
IO-390-EXP	220 HP	315 lbs (angle)

I’m also talking to Aero Sport Power as I’d love to build my engine. After all, part of the reason I chose to go experimental is so that I can do my maintenance. How could I do that if I don’t have a deep understanding of the entire plane? Aero Sport Power will sell you an engine kit and assemble it with your help so you know everything in it.

AeroSport Power offers an engine based on the IO-360 called the IO-375. This engine, by default, will offer 195, 200, or 205 horsepower, depending on cylinder compressions. All three options weigh 6 lbs more than a standard IO-360 180HP engine.

IO-375

205 HP

296 lbs (parallel)

You can reduce this weight with lightweight rings and induction sumps. Then, we need to add an inverted oil system to it, so I’m sure that the entire AEIO-375-M1S will net out around 300 lbs.

The IO-375 (and the aerobatic version, the AEIO-375) has a counterweighted crankshaft, which is essential to note when looking for a propeller. After limiting my search to constant-speed aerobatic props, the choice seems almost made for me. A Whirlwind 330-3B prop weighs 53 lbs, including the spinner and related hardware. Hartzel has yet to respond to my questions, and I still need to reach out to MT-Propeller before making any final decisions.

Having an aerobatic prop is essential because a standard constant-speed prop can overspeed when inverted for any length of time due to a drop in oil pressure. Aerobatic props work with counterweighted governers that force the prop to a coarse angle, thereby preventing any overspeed condition.