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I know this has been discussed before so please forgive me. I’m considering buying a 6 that is currently for sale. It’s a 6 not a 6A. It has the O-320 160 HP up front. It’s got about 40 hours since major. The owner says they get about 160 mph at 5k and 2400 RPM. That works out to about 140kts. I’ve read that people get 150-155kts in the 6. So where am I going wrong here or what am I missing?
Van's RV are one of the kits that was sold back in the day to present that actually did what was advertised. Issues with speed? Could be different things. Have a picture?
"The owner says they get about 160 mph at 5k and 2400 RPM"
What is the fuel burn? It sounds like he has it throttled back. To compare apples and apples you should fly it FULL THROTTLE at Sea level and ALSO at 8,000 feet WOT. These are typical standard bench marks. This might not be possible if the prop is under pitched and over revs (2700 RPM). However you can over rev the engine slightly, I'd recommend not going over 2800 rpm (although people drive around all day at 2900 RPM).
Yes his AS and RPM instruments may be off. As recommended do at least three leg triangle, fly constant heading (note GPS GS and tracks) and average all three GPS speeds.
What is the empty weight and CG?
Fit and finish. Fairings, rigging?
40 hrs SMOH Engine? OK I am not saying don't trust but verify. Who did the OH and what was replaced, reconditioned? I'd look at all the receipts and do a compression test. I'd check oil use, fly the thing an hour or three and check oil use. (Note Lycs blow off the anything over 6 qts quickly even if they say they hold 8 qts so don't top it off with oil). SMOH means different things to different people. Why did he OH it? Prop strike? Engine issues?
A strong 160HP engine should pull that RV through the air nicely. Don't insult the guy but it is reasonable to ask questions. A good OH is going to cost $10,000 to $15,000 with new jugs (wild guess from memory it may be different today). Did they OH the Mags and Carb? The price should reflect this. If it is cheap I'd be suspicious.
PROP - At WOT and RPM at SL should be able to over rev the engine... (Red Line is 2700). If it can't pull over 2700 RPM it means it has too much prop pitch. Way too high vise verse. Both will affect your speed.
It is possible the engine under powered (not making 160HP) or airframe too draggy.
What kind of exhaust does it have? Cross Over? 4 into 4? 2 into 1 each side (the worst design).
Van gets his data from a stock airframe with good workmanship, good stock Lyc and always LIGHT WEIGHT. Weight is a factor in speed. A clean 160HP RV-6 should be able to do (75% power) 191MPH (166 Kts) to (55%) 172 MPH (149.5 Kts). You are 10 Kts slow assuming he is quoting 55% power, which is a lot. Top speed WOT sea level should be around 200MPH.