DaleB
Well Known Member
Up until now I've been pretty much settled on a 180HP O- or IO-360 for my plane, mostly because that seems to be the norm for a -7. Today, though, I got to looking at the actual performance numbers, and figured out the actual difference in flying time to various destinations we'd be likely to fly to regularly (or even infrequently) with 160 and 180 HP. Using the numbers published on the Van's site, I come up with a worst case difference in flight time of about 15 minutes at economy cruise settings, not adjusted for winds. That's on flights from here in the middle of the country to pretty much either coast; most flights were 5-10 minutes difference.
So now I'm re-considering. It seems that O-320s are quite a bit more plentiful and less expensive than O-360s, although most of the 320s seem to have solid cranks for FP props. I have not yet changed my mind, but I'm certainly thinking I may expend my engine search pool.
I see some difference in takeoff and climb performance, but certainly not enough to be a deciding factor - it looks like an RV-7 pushed along Fred Flintstone style would perform well. I'm not looking to wring every last knot out of the plane. An RV-9 would probably have fit my mission just as well if not slightly better, but I liked the options I'd have open with the 7 - and I got a great deal on the kit. Resale value aside, are there reasons to go with the 180HP or higher 360 vs the 320 -- or vice versa? At the same speed, for example, would one burn significantly less fuel than the other?
So now I'm re-considering. It seems that O-320s are quite a bit more plentiful and less expensive than O-360s, although most of the 320s seem to have solid cranks for FP props. I have not yet changed my mind, but I'm certainly thinking I may expend my engine search pool.
I see some difference in takeoff and climb performance, but certainly not enough to be a deciding factor - it looks like an RV-7 pushed along Fred Flintstone style would perform well. I'm not looking to wring every last knot out of the plane. An RV-9 would probably have fit my mission just as well if not slightly better, but I liked the options I'd have open with the 7 - and I got a great deal on the kit. Resale value aside, are there reasons to go with the 180HP or higher 360 vs the 320 -- or vice versa? At the same speed, for example, would one burn significantly less fuel than the other?