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08-07-2022, 10:47 PM
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Join Date: Aug 2022
Location: Edmond, OK
Posts: 1
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IO-390 vs IO-360
I知 new to the group and looking to buy an 8 in the near future. Can anyone give insight about whether there is a noticeable difference between these two engines in performance.
Thanks for the help!
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08-07-2022, 11:30 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 16,607
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Welcome to VAF
Chad, welcome aboard the good ship VAF 
__________________
Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010
Phase 1 done, 2/4/2011 
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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08-07-2022, 11:43 PM
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Join Date: Nov 2018
Location: Nanaimo BC Canada
Posts: 176
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I suspect you値l notice a bit more speed but probably not a lot however the additional hp will really show in takeoff and climb. 
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08-08-2022, 11:45 AM
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Join Date: May 2017
Location: VA
Posts: 242
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It will reduce the weight of your wallet about $12,000 more than a 180hp io-360
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RV-8A Project
2022 Dues Paid
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08-08-2022, 12:02 PM
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Join Date: Mar 2009
Location: Colleyville
Posts: 318
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Its a significant difference from my 8a I had with a 180, my 390 At 8500 ft. 68% power 175 kt. TAS 8.3 gph (22 m.p. 2400 RPM) your prop could change the numbers quite a bit.
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Tim Blake
Colleyville, Tx
RV8a Purchased flying (many changes) Sold
RV-10 Purchased flying.. Panel upgrade complete.
G3X/Dynon/TT all new interior. Flyin like a dream. Sold
RV8a Purchased flying Let the changes begin
Last edited by Tim 8-A : 08-08-2022 at 12:07 PM.
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08-08-2022, 12:03 PM
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VAF Moderator / Line Boy
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 13,308
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“I wish I had less horsepower!”…..said no pilot, ever!
But honestly, the difference in performance between the two (assuming you;re talking angle valve to angle valve) is going to be pretty small. And also honestly, I have heard a number of guys with LOTS of RV-8 time that built a plane with an angle valve engine muse that if they built another one, they’d just go with a parallel valve engine because it makes the nose lighter, which makes for lighter handling.
Van originally designed the -8 for an O-320, but very, very few build that way!
With my 180 horsepower O-360, dual P-Mags, I cruised to and from Oshkosh this year at 170 KTAS burning about 8.8 gph. that’s just a data point, not a recommendation - just to help quantify things.
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Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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08-08-2022, 12:38 PM
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Join Date: Nov 2017
Location: Orlando
Posts: 950
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Parallel valve:
Stroked to 370-ish CIs
better breathing sump
EI
etc.
The HP numbers are then very close to the 390 at less weight and cost.
Yes, you could do much of the same to the 390 but a more economical path to 205->210-ish HP. Just another option to inform and cloud the OP's mind.
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08-08-2022, 01:28 PM
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Join Date: Aug 2009
Location: Goodyear, Arizona
Posts: 988
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Quote:
Originally Posted by Ironflight
的 wish I had less horsepower!賠..said no pilot, ever! 
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That gave me a good chuckle Paul. So true!
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Karl, Goodyear, Arizona (KGYR) ATP, CFII
RV-14A
Yak 50 Red Thunder Airshows
=VAF= donor 2023
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09-03-2022, 09:24 AM
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Join Date: Jan 2022
Location: OKC
Posts: 41
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Quote:
Originally Posted by Ironflight
“I wish I had less horsepower!”…..said no pilot, ever!
But honestly, the difference in performance between the two (assuming you;re talking angle valve to angle valve) is going to be pretty small. And also honestly, I have heard a number of guys with LOTS of RV-8 time that built a plane with an angle valve engine muse that if they built another one, they’d just go with a parallel valve engine because it makes the nose lighter, which makes for lighter handling.
Van originally designed the -8 for an O-320, but very, very few build that way!
With my 180 horsepower O-360, dual P-Mags, I cruised to and from Oshkosh this year at 170 KTAS burning about 8.8 gph. that’s just a data point, not a recommendation - just to help quantify things.
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Count me as one of those guys that built an 8 with an angle valve IO-360A1B6 that would re-build with a parallel valve, non-counterweighted crankshaft (but still with fuel injection) if I could do it over again. It was a plus when doing cross country with a person and full luggage. But I mostly flew solo and it was a negative for me when doing acro. Heavier stick forces than I like pulling through the bottom of maneuvers.
Last edited by Lucmac : 09-03-2022 at 09:26 AM.
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10-04-2022, 08:51 AM
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Join Date: Mar 2005
Location: SE Florida
Posts: 1,617
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Quote:
Originally Posted by cjjohns79
I知 new to the group and looking to buy an 8 in the near future. Can anyone give insight about whether there is a noticeable difference between these two engines in performance.
Thanks for the help!
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