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01-02-2013, 09:47 PM
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Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
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Scot
I see that you have practised this work before. Must be a bit frustrating.
Aside from all the giggles, I seriously doubt that there is anything you could do to cause this.
Quite simply, these kind of valve issues (often on genuine TCM jugs) are "birth defects" and when I assume, that these were replaced once before with the ECI ADa couple of years ago, they may well have been assembled poorly in the rush.
If ever there is a time for something like this to happen it is when the load is high and the pressure is on to turn around hundreds of customers "re-works".
I may be wrong...
Bummer all the same.
Did you pick this up from boroscoping? Leak down or suspect it from an engine monitor reading?
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David Brown
DYNON Authorised Dealer and Installer
The two best investments you can make, by any financial test, an EMS and APS!
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01-03-2013, 05:46 AM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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You guys can't look at the pic and tell what happened?
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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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01-03-2013, 05:54 AM
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Join Date: Mar 2006
Location: Austin, TX
Posts: 311
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Low Compression
While I think Dan may be right on the cause, Dave had the right answer on the 2nd reply - came in low on a compression test.
160HP running 100LL
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CQ Headset by Card Machine Works
CMW E-Lift
The other half of a flying RV-9A and an 8 in the shop.
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01-03-2013, 06:04 AM
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Join Date: Jan 2005
Location: Marion IA
Posts: 1,095
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Yay! What do I win
Sorry this happened to you guys. By the way since your website is gone I can't seem to finish my plane 
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Dave Gribble VAF #232
Building RV-9A N149DG (slider, IO-320, IFR)
Restored and Flying Beech Super III N3698Q
Marion IA
Struggling with fiberglass
There is no sport equal to that which aviators enjoy while being carried through the air on great white wings." Wilbur Wright, 1905
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01-03-2013, 06:42 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by tcard
While I think Dan may be right on the cause, Dave had the right answer on the 2nd reply - came in low on a compression test.
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Seriously, regarding the underlying fault I'm with David from Oz.....a birth defect.
Besides, you're a great pilot. And the peanut butter things were great. And yeah, now I'm kissing up because I like my cookies orally rather than, well, you know. 
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Dan Horton
RV-8 SS
Barrett IO-390
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01-03-2013, 07:36 AM
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Join Date: Aug 2006
Location: Taylor Texas
Posts: 811
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Not really...
Quote:
Originally Posted by rocketbob
You guys can't look at the pic and tell what happened?
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Lighten up, Francis.
What happened: burned valve. You can tell us why.
Carry on!
Mark
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01-03-2013, 07:47 AM
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Join Date: Jan 2005
Location: Littleton, CO
Posts: 367
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Bummer...
Wow, just saw this. Bummer Scott and Tanya. At least you guys caught it before something more severe happened. I'm headed to Amarillo on Sunday for a couple weeks. I was going to call you and see if you wanted to go to the Hard Eight the following weekend. Looks like that's out now.
Scott
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Scott Mills, Front Range, CO
N339A - 1900 Hours!! since 9/11/05
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Airport Landings
"In order to discover new lands one must have the courage to lose sight of the shore." Andre Gide
"Never feel sorry for a man who owns a plane" Charles Morse (Anthony Hopkins) in The Edge
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01-03-2013, 08:28 AM
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Join Date: Jun 2006
Location: 8I3
Posts: 3,564
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The only way an exhaust valve can burn up with that little time on it is from a manufacturing defect. The seat or valve had some error in grinding. Over time a small leak develops and a portion of the valve starts slowly eroding. This is why when I get a cylinder from a shop I disassemble and laps the valves and use hi-spot scraping blue to make sure the valves seat properly. None of the manufacturers and most of the cylinder shops don't do this. I'm set up now to do my own seats now with a nifty set of tools to put a three-way valve job on. To my knowledge only Lycon does the same thing.
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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.
Last edited by rocketbob : 01-03-2013 at 08:33 AM.
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01-03-2013, 08:36 AM
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Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,156
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Sorry for my absence in the technical discussion, real work happens, and I usually just come to VAF just for entertainment these days.
I've been watching this cylinder for about four months and about 125hrs. The very first indication, very early on, was from pulling the prop through. You feel three nice and tight cylinders and one that was becoming just a little more 'soft'. I did a whole lot of "just go fly and keep a close eye on it". We do 25hr oil changes, so on the next oil change, we did a compression test. Yep, it was down a little from its normal but still perfectly fine. It continued to get a little softer and the compression tests accelerated to the point where my arm is very highly calibrated. I can feel just a couple of pounds change now  . So, I'm paying close attention to engine instrumentation and the rest of the potential indicators. Next look, about 10-15hrs later, with compression still well in the 70s, I decided it was time to figure out exactly where the leakdown was coming from. This ain't rocket science. Pressurize the cylinder and stick an ear up to the exhaust stack exit. "Wooohhhhhh." We did a few of the normal 'valve gymnastics' while we continued to fly. No change. I kept a close eye on it with my now highly calibrated arm. As the compression fell into the 60s, it was clear to me what the end game was. I just had to decide for myself When. That point came this past weekend when Tanya wanted to go do a dog rescue for pilots-n-paws and I said "Sorry, you can't go", as I held my head in shame. The cylinder was off within 12hrs.
So, I've decided that I'm not going to fly around anymore without the ability to look inside my cylinders any ol' time I want. A Mills style 'borescope' is on its way and will be here tomorrow. Now to dump a little more fuel on this fire... I have another cylinder that I've been watching too! Same symptoms, same process, same progression, same product batch. It isn't quite there yet, but I'm not flying it until I'm able to take a good look inside. It might be off as well, depending on what I see this weekend.
Don't feel sorry for me. I enjoy this stuff. Removing and replacing a cylinder just isn't any big deal. "Field replaceable" design is my friend. My airplane likes to be maintained. Feel sorry for Tanya, she has to write the checks  .
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Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
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01-03-2013, 08:45 AM
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Join Date: Jan 2007
Location: Stuart, FL /Hartford, CT/Virgin Gorda,BVI
Posts: 3,122
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scott, do you have any info on the borescope you are planning on getting. cost, contact? thanks 
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Ed D'Arcy
RV6-A 5,200+ hrs, R-44 1,600 hrs, Helicycle 320 hrs, gyro sold,35,000 miles flown in 2015 
Stuart, Fl / S WINDSOR,Ct / Virgin Gorda, BVI - under major repair from hurricane damage
VAF #840 EAA AOPA FAC FABA QB SPA
addicted pickle ball player
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