X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 30 Jan 2012 07:51:02 -0500 Message-ID: X-Original-Return-Path: Received: from mail-lpp01m010-f52.google.com ([209.85.215.52] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTPS id 5369495 for lml@lancaironline.net; Mon, 30 Jan 2012 00:23:36 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.215.52; envelope-from=indigoaviation@gmail.com Received: by lagy4 with SMTP id y4so1052547lag.25 for ; Sun, 29 Jan 2012 21:23:00 -0800 (PST) MIME-Version: 1.0 Received: by 10.112.24.129 with SMTP id u1mr4203633lbf.8.1327900980651; Sun, 29 Jan 2012 21:23:00 -0800 (PST) Received: by 10.112.45.33 with HTTP; Sun, 29 Jan 2012 21:23:00 -0800 (PST) In-Reply-To: References: X-Original-Date: Mon, 30 Jan 2012 00:23:00 -0500 X-Original-Message-ID: Subject: Re: [LML] Re: Lycoming exhaust valve questions From: swaid rahn X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=e0cb4efe2ff23fa56f04b7b80a07 --e0cb4efe2ff23fa56f04b7b80a07 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Gentlemen, My post to Dan is not a dare or a challenge here on this forum, it is merely trying to pass on the information that I would give to my other customers. Notice I recommended to run/fly the aircraft and take another reading before pulling the cyl. and that a compression test is not all inclusive but you need other information to properly analyze the condition of your engine/cyl. I am glad someone posted some service information here as I don't like to work from memory alone or paraphrase tech. info because that leads to errors. Because I am an aircraft owner, pilot and mechanic I have a three sided point of view. Dan said he had a leaking exhaust valve. If it does not "clear up" after a one hour maintenance flight it probably won't after a 2,3,4, or 20hr. test flight but I would check it a few times to be sure. Because I know that Lycoming exhaust valves are sodium filled 1/2 diameter shanked valves and assembled with .005" clearance when new and are allowed to wear .001" per 100 hours after 300 initial hours excessive heat will destroy the valve guide very quickly as the table of limits allow up to a total of .018" guide to stem clearance as the service max( which is really loose). If the valve is leaking at the seat it cannot transfer the stored heat to the valve seat/head which will accelerate the wear on the valve stem. My concerns: Owner- I don't want to spend anymore money than I have to to keep my aircraft airworthy. Ex valves alone are over $230 each. Pilot- I don't want this engine to drop a valve and cause me to have to get it repaired on a cross country flight at a shop I don't know, rental car home & back, or worse. Mechanic- I don't want to send out a cyl. for a guide replacement, seat grind or weld repair while tieing up my hangar space, extra down time, having to box and ship, phone repair shop, float expenses on my credit card when I could have fixed it by lapping the valve on the bench for 15 min. and a $20 gasket set. There are many good reasons to fix things early before they become real problems. Also my wife and family like it better when we fly somewhere and can come back on our own schedule and not the airplanes. My wife and family do not have unconditional love for airplanes like most mechanics I have met they just expect flawless performance 100% of the time. Most mechanics like myself understand that when proper care and maintenance is not performed on aircraft the aircraft will breakdown and wear out sooner than they should. Short cuts and differed maintenance usually lead to larger repairs and more money and more down time and nobody wants that. And contrary to some beliefs here most mechanics don't "love it because it is a great revenue generator" about pulling cylinders. It ties up hangar space and screws up schedules for all involved. I don't like to see customers have to endure large unscheduled maintenance expenses just as I would not want to either. Quote-"Traditional A and P's hate this suggestion. It flies in the face of the traditions developed fifty years ago. But this is 2012 and there are a lo= t more data available. The procedure outlined by Continental is what is known as "best known method" today. Tomorrow something better may surface." The Traditional A&P'S that I know and work with usually spend a good bit of time reading the manufacturers service information, after all it is required by FAR to do so. And the service bulletin referred to above is a revision to the one that came out around 1996. A older mechanic at my competitors shop told me about the master orifice and helped me calibrate my compression tester in 1996. He got his A&P license in the 1940's. BTW he is not in it "just for the money "either. Just like me most of his customers are his personal friends also. Most mechanics I know take real pride in their profession and are always learning and trying to improve themselves, like most pilots I know. So here is the question. Which is more noble? An A&P mechanic who loves aircraft so much that he wants to learn to fly them so he can understand them more OR a pilot who loves aircraft so much that he wants to learn to work on them or build one so he can understand them more? I think at the end of the day maybe we are just all aviators. Respectfully, Swaid Rahn On Sun, Jan 29, 2012 at 8:47 PM, John Hafen wrote: > Thanks Swain. > > Very Helpful. > > On Jan 29, 2012, at 2:16 PM, Colyn Case wrote: > > I think Swain's main point is you don't want to let the exhaust valve go > if it's starting to get a hot spot. Leaks are associated with bad seal = at > the valve. maybe worry more about the bore scope than the compression > reading? > > re: the change interval, you might find this article informative: > http://www.avweb.com/news/savvyaviator/savvy_aviator_52_thinking_about_oi= l_changes_196730-1.html > > > On Jan 27, 2012, at 11:06 AM, Gary Casey wrote: > > Okay, I'll take the dare from Swain and post what might be the more > "normal" reply :-). I think he is being a little of a perfectionist. I > don't have his credentials, but from what I have seen, a compression > leakage of 74 to 76 is the most common. A compression number up to 78 > suggests that the engine is pumping excess oil past the rings and the oil > is sealing that leak path. So I would worry more about the ones that > measure 78 than I would about the one that is at 75. Assuming you check > the compression every 100 hours or so, I would wait until you have more > than 2 compression tests with ever-dropping values before I would even > start to worry. That will take another 200 hours of operation. I wouldn= 't > worry until the compression dropped below 70. And like Dan said, it is > always a good idea to warm the engine and then do the compression test as > soon as possible afterward. I've gone as far as to warm the engine with > the cowl off so I could do it faster, but to just idle on the ground is n= ot > a good thing just before a compression test. If I were really into the > diagnostics I would warm the engine (cowl off) at the normal runup rpm an= d > then run it at full power for maybe 15 seconds, pulling the mixture while > at full power to get a "clean" shut-off. Then you'll get as good a test = as > possible. > > And why do you change oil every 25-35 hours? With a modern engine and > modern oil, I don't see any reason to change oil that often. I would run > it at least 50 hours and try to change it before 75. If the engine is ru= n > often, even 100 hours isn't out of line. What does the oil look like at > the oil change? Can you see the dipstick through the oil? If so, it > probably doesn't need to be changed yet. > Gary > > Previously, from Swain: > Hi Dan, > My opinion will differ from most here. It is based on 28 years as a > professional aircraft mechanic and a cylinder overhaul shop owner for 17 > years. Lycoming says that NO static leakage is allowed during a compressi= on > test and I agree. What will happen is that if your ex. valve continues to > leak past it's seat it will errode a gas path in the seat and valve face. > This will cause a "hot spot" in that area that can eventually lead to > valve face breakage which might do major damage to one or more cyl. I say > more than one because I have personally seen a piece of ex. valve leave > it's cyl. through it's intake port and enter the next cyl. beside it and > lodge itself into the face of that piston while bending the other cyl. > intake valve. (BTW I keep that piece of valve in my desk drawer as a > reminder of what can happen). The only way a valve can cool itself is > through the time it sits on it's valve seat to transfer heat from the val= ve > to the head and also through the valve stem. That's why when guides get > worn and seats leak you wear out valve stems and guides much quicker, the= re > is not as much metal contact for cooling and the psi of force on the wear > surfaces increases (same force less wear surface). > Remember one compression test is only a snapshot of what is happening in > your engine. You need more than one and other information to develope a > trend on what your engine is really doing. > I would go fly your airplane at high power settings for one hour and com= e > back and take another compression test. Then you might try some of the > tricks mentioned here ( I have never had much luck with short cuts). If i= t > was my airplane I would pull the cyl. and fix the problem and not screw > around with wobble test, staking the valve, or trying to lap a valve > without pulling the cyl. A gasket set is less than $20 bucks and you don'= t > have to replace the rings if there are serviceable and you don't hone the > cyl.. > I have repaired/overhauled over a 1000 Continental and Lycoming cylinder= s > and it does not take very long to R&R a cyl. > Swaid Rahn > A&P,I.A.,ATP > LIVP-T(Walter) > LIVP-T(Garrett under construction) > > > > On Tue, Jan 24, 2012 at 11:06 AM, Dan & Kari Olsen > wrote: > > LML Gang,**** > ** ** > Doing the annual on my 320 this week. Compression check shows 77-78 on > cylinders 1, 2, 4. #3 is 75 and I hear pretty good leakage through the > exhaust, indicating a leaking exhaust valve. I=92ve had no indication of > sticking valves or morning sickness. I pulled the rocker cover and there > is no abnormality there. This engine is typically run lean of peak at > power settings of 55-65% power. Oil changes every 25-35hrs. Engine has > 623hrs since new.**** > ** ** > My question to those of you who are much more experienced with the > Lycoming 4-cylinder engines, is what should be my next course of action?*= * > ** > **=B7 **Do the valve lapping procedure per the Lyc service > instruction?**** > **=B7 **Start using TCP and re-check in a few hours?**** > **=B7 **Go run the engine hard and re-check the compression?**** > **=B7 **Something else?**** > ** ** > I really want to nip this in the bud and not end up with a burned exhaust > valve, requiring pulling a jug.**** > ** ** > Appreciate your thoughts and responses.**** > ** ** > Cheers!**** > ** ** > Dan Olsen > > > > --=20 Swaid L. Rahn Indigo Aviation, Inc. 940 Mock Road Springfield, Ga. 31329 Cell 912.655.0966 --e0cb4efe2ff23fa56f04b7b80a07 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Gentlemen,
=A0My post to Dan is not a dare or a challenge he= re on this forum, it is merely trying to pass on the information that I wou= ld give to my other customers. Notice I recommended to run/fly the aircraft= and take another reading before pulling the cyl. and that a compression te= st is not all inclusive but you need other information to properly analyze = the condition of your engine/cyl. I am glad someone posted some service inf= ormation here as I don't like to work from memory alone or paraphrase t= ech. info because that leads to errors. Because I am an aircraft owner, pil= ot and mechanic I have a three sided point of view. Dan said he had a leaki= ng exhaust valve. If it does not "clear up" after a one hour main= tenance flight it probably won't after a 2,3,4, or 20hr. test flight bu= t I would check it a few times to be sure.=A0Because I know that Lycoming e= xhaust valves are sodium filled 1/2 diameter shanked valves and assembled w= ith .005" clearance when new and are allowed to wear .001" per 10= 0 hours after 300 initial hours excessive heat will destroy the valve guide= very quickly as the table of limits allow up to a total of .018" guid= e to stem clearance as the service max( which is really loose). If the valv= e is leaking at the seat it cannot transfer the stored heat to the valve se= at/head=A0which will accelerate the wear on the valve stem.
=A0My concerns:
Owner-=A0 =A0I don't want to spend anymo= re money than I have to to keep my aircraft airworthy. Ex valves alone are = over $230 each.
Pilot-=A0 =A0I don't want this engine to drop= a valve and cause me to have to get it repaired on a cross country flight = at a shop I don't know, rental car home & back, or worse.
Mechanic- I don't want to send out a cyl.=A0for a guide replacemen= t, seat grind or=A0weld repair while tieing up my hangar space, extra down = time,=A0having to box and ship, phone=A0repair shop, float expenses on my c= redit card=A0when I could have fixed it by lapping the valve on the bench f= or 15 min. and a $20 gasket set.
=A0There are many good reasons to fix things early before they become real = problems. Also my wife and family like it better when we fly somewhere and = can come back on our own schedule and not the airplanes. My wife and family= do not have unconditional love for airplanes like most mechanics I have me= t they just expect flawless performance 100% of the time. Most mechanics li= ke myself understand that when proper care and maintenance is not performed= on aircraft the aircraft will breakdown and wear out sooner than they shou= ld. Short cuts and differed maintenance usually lead to larger repairs and = more money and more down time and nobody wants that.
=A0And contrary to some beliefs here=A0most mechanics don't "= love it because it is a great revenue generator" about pulling cylinde= rs. It ties up hangar space and screws up schedules for all involved. I don= 't like to see customers have to=A0endure large unscheduled maintenance= expenses just as I would not want to either.
=A0
Quote-"Traditional A and P's hate this suggesti= on. It flies in the face of the
=A0traditions developed fifty years ago.= =A0 But this is 2012 and there are a lot
=A0more data available.=A0=A0 T= he procedure outlined by Continental is what is
=A0known as "best known method" today.=A0 Tomorrow something bett= er may surface."
=A0
The Traditional A&P'S= that I know and work with usually spend a good bit of time reading the man= ufacturers service information, after all it is required by FAR to do so. A= nd the service bulletin referred to above is a revision=A0to the one that= =A0came out around 1996. A older mechanic at my competitors shop told me ab= out the master orifice and=A0helped me=A0calibrate my compression tester in= 1996. He got his A&P license in the 1940's. BTW he is not in it &q= uot;just for the money "either. Just like me most of his customers are= his personal friends also.
Most mechanics I know take real pride in their profession and are alwa= ys learning and trying to improve themselves, like most pilots I know.
=A0So here is the question. Which is more noble? An A&P mechanic = who loves aircraft so much that he wants to learn to fly them so he can und= erstand them more OR a pilot who loves aircraft so much that he wants to le= arn to work on them or build one so he can understand them more?
=A0I think at the end of the day maybe we are just all aviators.
=
Respectfully,
Swaid Rahn

=A0
On Sun, Jan 29, 2012 at 8:47 PM, John Hafen <j.hafen@comcast.net><= /span> wrote:
Thanks Swain.

=
Very Helpful.

On Jan 29, 201= 2, at 2:16 PM, Colyn Case wrote:

I think Swain's main point is you don't = want to let the exhaust valve go if it's starting to get a hot spot. = =A0 Leaks are associated with bad seal at the valve. =A0 maybe worry more a= bout the bore scope than the compression reading?

re: the change interval, you might find this article informa= tive: =A0http://www.avw= eb.com/news/savvyaviator/savvy_aviator_52_thinking_about_oil_changes_196730= -1.html


On Jan 27, 2012, = at 11:06 AM, Gary Casey wrote:

Okay, I'll take the dare from Swain and post what might be the more &qu= ot;normal" reply :-). =A0I think he is being a little of a perfectioni= st. =A0I don't have his credentials, but from what I have seen, a compr= ession leakage of 74 to 76 is the most common. =A0A compression number up t= o 78 suggests that the engine is pumping excess oil past the rings and the = oil is sealing that leak path. =A0So I would worry more about the ones that= measure 78 than I would about the one that is at 75. =A0Assuming you check= the compression every 100 hours or so, I would wait until you have more th= an 2 compression tests with ever-dropping values before I would even start = to worry. =A0That will take another 200 hours of operation. =A0I wouldn't worry until the com= pression dropped below 70. =A0And like Dan said, it is always a good idea t= o warm the engine and then do the compression test as soon as possible afte= rward. =A0I've gone as far as to warm the engine with the cowl off so I= could do it faster, but to just idle on the ground is not a good thing jus= t before a compression test. =A0If I were really into the diagnostics I wou= ld warm the engine (cowl off) at the normal runup rpm and then run it at fu= ll power for maybe 15 seconds, pulling the mixture while at full power to g= et a "clean" shut-off. =A0Then you'll get as good a test as p= ossible.

And why do you change oil every 25-35= hours? =A0With a modern engine and modern oil, I don't see any reason = to change oil that often. =A0I would run it at least 50 hours and try to ch= ange it before 75. =A0If the engine is run often, even 100 hours isn't = out of line. =A0What does the oil look like at the oil change? =A0Can you see = the dipstick through the oil? =A0If so, it probably doesn't need to be = changed yet.
Gary

Previously, from Swain= :=A0
Hi Dan,
=A0My opinion will diffe= r from most here. It is based on 28 years as a professional aircraft mechan= ic and a cylinder overhaul shop owner for 17 years. Lycoming says that NO s= tatic leakage is allowed during a compression test and I agree. What will h= appen is that if your ex. valve continues to leak past it's seat it wil= l errode a gas path in the seat and valve face. This will cause a "hot= spot" in that area that can eventually lead to=A0 valve face breakage= which might do major damage to one or more cyl. I say more than one becaus= e I have personally seen a piece of ex. valve leave it's cyl. through it's intake port and en= ter the next cyl. beside it and lodge itself into the face of that piston w= hile bending the other cyl. intake valve. (BTW I keep that piece of valve i= n my desk drawer as a reminder of what can happen). The only way a valve ca= n cool itself is through the time it sits on it's valve seat to transfe= r heat from the valve to the head and also through the valve stem. That'= ;s why when guides get worn and seats leak you wear out valve stems and gui= des much=A0quicker, there is not as much metal contact for cooling and the = psi of force on the wear surfaces increases (same force less wear surface).=
=A0Remember one compression test is only a snapshot = of what is happening in your engine. You need more than one and other infor= mation to develope a trend on what your engine is really=A0doing.
=A0I would go fly your airplane at high power settings for one hour and co= me back and take another compression test. Then=A0you might=A0try some of the tric= ks mentioned here ( I have never had much luck with short cuts). If it was = my airplane I would pull the cyl. and fix the problem and not screw around = with wobble test, staking the valve, or trying to lap a valve without pulli= ng the cyl. A gasket set is less than $20 bucks and you don't have to r= eplace the rings if there are serviceable and you don't hone the cyl..<= /div>
=A0I have repaired/overhauled over a 1000 Continental and Lycoming cyl= inders and it does not take very long to R&R a cyl.
Swaid Rah= n
A&P,I.A.,ATP
LIVP-T(Walter)
LIVP-T(Garr= ett under construction)


=A0
On Tue, Jan 24, 2012 at 11:06 AM, Dan & Kari= Olsen=A0<olsen25@comcast.net>=A0wrote:=
LML Gang,
=A0
Doing the annual on my 320 this= week.=A0 Compression check shows 77-78 on cylinders 1, 2, 4.=A0 #3 is 75 a= nd I hear pretty good leakage through the exhaust, indicating a leaking exh= aust valve.=A0 I=92ve had no indication of sticking valves or morning sickn= ess.=A0 I pulled the rocker cover and there is no abnormality there.=A0 Thi= s engine is typically run lean of peak at power settings of 55-65% power.= =A0 Oil changes every 25-35hrs.=A0 Engine has 623hrs since new.
<= /u>=A0
My question to those of you who are much more experienced wi= th the Lycoming 4-cylinder engines, is what should be my next course of act= ion?
<= /u>=B7=A0=A0=A0=A0=A0=A0=A0= =A0=A0Do the valve lapping procedure per the Ly= c service instruction?
<= /u>=B7=A0=A0=A0=A0=A0=A0=A0= =A0=A0Start using TCP and re-check in a few hou= rs?
<= /u>=B7=A0=A0=A0=A0=A0=A0=A0= =A0=A0Go run the engine hard and re-check the c= ompression?
<= /u>=B7=A0=A0=A0=A0=A0=A0=A0= =A0=A0Something else?
=A0
I really want to nip this in the bud and not end up with= a burned exhaust valve, requiring pulling a jug.
=A0
Appreciate your thoughts and responses.
<= u>=A0
Chee= rs!
=A0
Dan Olsen




--
Swaid L. Ra= hn
Indigo Aviation, Inc.
940 Mock Road
Springfield, Ga. 31329
C= ell 912.655.0966


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