Engine size Pros and Cons

[keith6261]

Guys, I trying to decide what engine size for my 8.

[gasman]

Based on Van's latest prices, The O360 is the same price as the O320.

So...... at least get the O360.

[rv8ch]

I guess if we knew more about your "primary" mission it would help. Racing? Aero? Cross Country flying? Assuming you want a "normal" RV-8, get the exact engine/prop Van's recommends and your build and test time will be faster and easier.

Otherwise, anything from an 0-320 to an IO-540 will work, with tradeoffs.

[Desert Rat]

I just went through this exercise.

Spent hours online and with the calculator, looking at everything from fuel burn, to expected KTAS, to range profiles, to the price of replacement cylinders, to perceived difficulty of each installation. Carefully reviewed each response to my VAF thread where I asked for opinions.

I finally just said heck with it and bought the Thunderbolt IO390.

Probably can't justify it for my mission, But it's ultimately what I wanted.

Where I'm going with this is that you can ask for internet advice and crunch numbers all day long, but ultimately you have to make a decision you can live with and it may not be the most practical one. Only you can decide.

[Mel]

Desert Rat is exactly right. Unless you have a specific operating purpose, Van's recommended engine is usually the best option. More hp will give you more take-off and climb performance (As if the RV needed this), usually at the cost of money & weight, but very little, if any, cruise speed advantage.

Also, as Desert Rat points out, It's your airplane and it's experimental. If you want something in particular, do it!

[PilotjohnS]

But I chose the injected version of the Lycoming for two reasons: easier lean of peak operation, and no carb icing issues.
It seems the price difference is small. Also, it is amazing how many builders initially fly with a carb engine and than upgrade to fuel injection.

[abwaldal@gmail.com]

Easy answer. Big as you can afford that the airframe can handle. You can never have enough horses under the hood. Fuel economy is only a small factor. I love the bigger horses and fuel injection is necessary for good life in the air.
I would buy the I0-360 because it will fly and sell faster when the time comes.
Enjoy spending the money cause it is gonna be quite a bit. Art

[tjo]

Just my opinion, of course, but best HP/$ is O360. Injected, if you want. The only reason to go angle valve is to go O390. There is no reason to go O320 unless you find a great deal. Simple formula, direct result

Tim

[RYOUNG]

Desert Rat nailed it! I too originally planned an O-360 for my RV-8. Then after Van’s approved the IO-390 for use I was torn. After mulling over pros and cons for about a month, I bounced it off a good friend and his advice was “if you’re going to be a bear, be a grizzly”. That did it, along with the upcoming price increase. Now in the process of swapping out lower cowls with Van’s. Not looking back, full speed ahead. After all, what are friends for?

[keith6261]

So my mission would be some light aerobatics but mostly cruising. Just wondering what true speeds are seen between an IO360 to a IO390. Thanks for everyone's input.