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07-12-2014, 05:37 PM
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Join Date: Sep 2008
Location: California
Posts: 697
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New engine runs rough?
Just started up new from overhaul O-320 with ported cylinders and 9.5:1 pistons. One P-Mag, one Slick. Getting 100 RPM drop on either. Seems rough. And never had a drop on the EI before....
Neighbor A&P says it will smooth out as the rings seat and compression comes up. What do you think Mel, Walt, Smoky, RocketBob?
Thanks!
Taking a dinner break then will pull plugs and check timing.
Last edited by flyingriki : 07-12-2014 at 05:48 PM.
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07-12-2014, 05:59 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,668
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No reason for a new engine to run rough, fix it before you fly it!
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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07-12-2014, 06:21 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,515
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What do you mean rough? Unsteady speed, misfires, or more vibration in airframe, or uneven sound in the exhaust?
9.5:1 will give more feedback to the airframe.
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Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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07-12-2014, 06:29 PM
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Join Date: Sep 2008
Location: California
Posts: 697
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Quote:
Originally Posted by BillL
What do you mean rough? Unsteady speed, misfires, or more vibration in airframe, or uneven sound in the exhaust?
9.5:1 will give more feedback to the airframe.
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Doesn't seem like any plugs are not firing but it shakes a lot more than the 7:1 did, particularly at idle. Does idle slower. The RPM drop in the EI is not normal from my experience. Usually doesn't drop at all. I'm getting 100+ RPM drop on the EI and the Mag.
Throttle up is stuttering too. New behavior with same carb.
Last edited by flyingriki : 07-12-2014 at 06:36 PM.
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07-12-2014, 06:48 PM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,562
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Check your idle mixture.
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Please don't PM me! Email only!
Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
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07-12-2014, 06:48 PM
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Join Date: Aug 2007
Location: Wichita Falls, TX
Posts: 2,182
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A high compression engine will generally give a perceived feeling of running rougher than a similar lower-compression engine, but if it's really running rough, one of the first things I'd check on a carbureted Lyc is the intake tube hoses and gaskets for possible vacuum leaks. This seems to be somewhat of an Achilles Heel of Lyclone engines. I recently replaced the rubber intake tube hoses on my O-320 due to one of them getting baked from close proximity to the exhaust pipes and discovered that 3 of the 4 intake flange gaskets had been leaking quite badly. With new gaskets and rubber hose segments, my O-320 has never run smoother in the 150+ hours I've owned it. I also discovered that if you're not absolutely meticulous in your installation of the intake flange gaskets, you can easily screw them up and cause an induction leak and it's pretty easy to damage the gaskets upon installation... this might be something worth checking in a freshly assembled engine.
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Neal Howard
Airplaneless once again...
Last edited by Neal@F14 : 07-12-2014 at 06:54 PM.
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07-12-2014, 06:52 PM
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Join Date: Sep 2008
Location: California
Posts: 697
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I was extremely meticulous in installing the intakes. Careful gasketing, gasket cement, special clamps. etc....
Will check anyway.
Also the idle mixture Bob, thanks! Need to look up how to do that next....
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07-12-2014, 07:02 PM
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Join Date: Mar 2005
Location: Dallas area
Posts: 10,762
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When I went from 7:1 to 9.5:1 I noticed my engine was not quite as smooth as before, but I wouldn't call it "rough". It's more noticeable with a light-weight prop.
Once I went to the Catto 3-blade, my smoothness returned.
__________________
Mel Asberry, DAR since the last century.
EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
<rvmel(at)icloud.com>
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07-12-2014, 08:23 PM
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Join Date: Sep 2008
Location: California
Posts: 697
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Thanks Mel. I have a Catto 3 blade so no excuses for this. Guess I have a few things to check. Long Sunday....
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07-13-2014, 12:53 PM
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Join Date: Sep 2008
Location: California
Posts: 697
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Quote:
Originally Posted by rocketbob
Check your idle mixture.
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That's all it was, Thanks Bob! |
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