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Old 03-13-2017, 08:00 AM
jeffw@sc47's Avatar
jeffw@sc47 jeffw@sc47 is offline
 
Join Date: Aug 2014
Location: Simpsonville, SC (SC47)
Posts: 312
Default IO-390 with lower compression?
Is it feasible / possible to have a Lycoming IO-390 built with a lower compression than the standard 8.9:1 ratio? So it might be possible to burn Avgas 91 or 93, or even Mogas non-ethynol.

Edit add 3/13/17 >> Informed by Lycoming Thunderbolt that they can supply an IO-390 that will "run about 200 hp and would be able to run on 93 AKI fuel" they do not recommend octanes lower than 93_AKI.
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Jeff Warren
Simpsonville, SC (@SC47 > 10nm NW Triple Tree)
1946 Bellanca Cruisair 14-13-2 (73 YRS OLD 8/15/19)
RV14A (N14ZT), Ser#140195
Start 10/11/14
Dues paid 12/1/19 (USArmy 2/67-2/70)
www.mykitlog.com/jeffw@sc47
Last edited by jeffw@sc47 : 03-13-2017 at 04:20 PM.
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Old 03-13-2017, 09:20 AM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
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"1946 Bellanca Cruisair 14-13-2 (70 YRS OLD 8/15/16)
RV14A (N14ZT), Ser#140195"

Wouldn't it be wonderful if your Bellanca was still flying when N14ZT turns 70!!!
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built a few RVs, rebuilt a few more, hot rodded some, & maintained/updated a bunch more
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Old 03-13-2017, 09:49 AM
868RM 868RM is offline
 
Join Date: Oct 2009
Location: lena, il.
Posts: 305
Default 390 compression
Jeff, Lycon built me a 390 with .010 oversize bore and 8.7 to 1 a few years ago. First flight was July 2016 and now have 105 hrs. one it. They have their own forged pistons for .010 over. Runs great on pump gas and rings are finally seating. Also (2) P-mags with timing set at 20 degrees for now. Engine is not in a RV. Ron
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