X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 27 Jan 2012 11:06:49 -0500 Message-ID: X-Original-Return-Path: Received: from nm14-vm1.bullet.mail.ne1.yahoo.com ([98.138.91.38] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with SMTP id 5366759 for lml@lancaironline.net; Fri, 27 Jan 2012 08:31:47 -0500 Received-SPF: none receiver=logan.com; client-ip=98.138.91.38; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.50] by nm14.bullet.mail.ne1.yahoo.com with NNFMP; 27 Jan 2012 13:31:11 -0000 Received: from [98.138.89.162] by tm3.bullet.mail.ne1.yahoo.com with NNFMP; 27 Jan 2012 13:31:11 -0000 Received: from [127.0.0.1] by omp1018.mail.ne1.yahoo.com with NNFMP; 27 Jan 2012 13:31:11 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 567827.7365.bm@omp1018.mail.ne1.yahoo.com Received: (qmail 81629 invoked by uid 60001); 27 Jan 2012 13:31:11 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=hDMlqLmRUhwz1RYlv3iKlkGMsuH602KlbLYff0OVH+pSCfW5y/lkDygswaDDEoR2MFemtHO+Gdnfjw0YV8HSiBQfh96VPaRER1zShsfFzY+JTDluRKRE2Xkpe55mOWmCn0DRFwpzqlBz7ZOR1fafnkjYN/LlchuZVnApmT6IPPg=; X-YMail-OSG: zu7xrFMVM1n66SU09Wh8oOBgOhaD6b9zopVBreI43WHkxOY cQNaW5LQjQMPiVcHS8sHzR5nTWFJwCzZgiEFZrquj5X740u7yV6xIm_kYt25 iaG6UMbo52favVNZlSkerCErB26aFpNZBoE_Z9xFrc96XKo9O9DKMbURE7pX lfIP9cNbqq90gx7OWuSZv_dyn.xdQKmUqZm8ztSNGI6V0SY2VkRS7PPY_CoV shUEf458phj3jn2zAKxE9zPq1qcuD.jOTmqUNePS_c8Hwze5rjbIEW8MRRQD kMbiEFcAV62kZ5cCa_9x9TZxY4Pb4TGRJ6nE_OMlaJCJ.yk2lzhSyeZKnRoq L0qRysVBDsSQPWioOCIE2MrNdF2vIKV36H_i_5GFEpJTR_xpP4j8FXAJsvre vDZRxhGGLGvvs3AMuRCm1VzwJpNgGeS9gzRQI3fWYPBilb.4JDAOZt8412ou h Received: from [71.218.228.189] by web125606.mail.ne1.yahoo.com via HTTP; Fri, 27 Jan 2012 05:31:11 PST X-Mailer: YahooMailWebService/0.8.116.331537 References: X-Original-Message-ID: <1327671071.60985.YahooMailNeo@web125606.mail.ne1.yahoo.com> X-Original-Date: Fri, 27 Jan 2012 05:31:11 -0800 (PST) From: Gary Casey Reply-To: Gary Casey Subject: Re: Lycoming exhaust valve questions X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="607277540-1731264335-1327671071=:60985" --607277540-1731264335-1327671071=:60985 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Okay, I'll take the dare from Swain and post what might be the more "normal= " reply :-). =C2=A0I think he is being a little of a perfectionist. =C2=A0I= don't have his credentials, but from what I have seen, a compression leaka= ge of 74 to 76 is the most common. =C2=A0A compression number up to 78 sugg= ests that the engine is pumping excess oil past the rings and the oil is se= aling that leak path. =C2=A0So I would worry more about the ones that measu= re 78 than I would about the one that is at 75. =C2=A0Assuming you check th= e 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. =C2=A0That will take another 200 hours of operation. =C2=A0I wouldn'= t worry until the compression dropped below 70. =C2=A0And like Dan said, it= is always a good idea to warm the engine and then do the compression test = as soon as possible afterward. =C2=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 just befo= re a compression test. =C2=A0If I were really into the diagnostics I would = warm the engine (cowl off) at the normal runup rpm and then run it at full = power for maybe 15 seconds, pulling the mixture while at full power to get = a "clean" shut-off. =C2=A0Then you'll get as good a test as possible.=0A=0A= And why do you change oil every 25-35 hours? =C2=A0With a modern engine and= modern oil, I don't see any reason to change oil that often. =C2=A0I would= run it at least 50 hours and try to change it before 75. =C2=A0If the engi= ne is run often, even 100 hours isn't out of line. =C2=A0What does the oil = look like at the oil change? =C2=A0Can you see the dipstick through the oil= ? =C2=A0If so, it probably doesn't need to be changed yet.=0AGary=0A=0APrev= iously, from Swain:=C2=A0Hi Dan,=0A=C2=A0My opinion will differ from most h= ere. It is based on 28 years as a professional aircraft mechanic and a cyli= nder overhaul shop owner for 17 years. Lycoming says that NO static leakage= is allowed during a compression 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 pa= th in the seat and valve face. This will cause a "hot spot" in that area th= at can eventually lead to=C2=A0 valve face breakage which might do major da= mage 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 th= e next cyl. beside it and lodge itself into the face of that piston while b= ending the other cyl. intake valve. (BTW I keep that piece of valve in my d= esk 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 fro= m 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 guides much=C2=A0quicker, there is not as much me= tal contact for cooling and the psi of force on the wear surfaces increases= (same force less wear surface).=0A=C2=A0Remember one compression test is o= nly 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=C2= =A0doing.=0A=C2=A0I would go fly your airplane at high power settings for o= ne hour and come back and take another compression test. Then=C2=A0you migh= t=C2=A0try some of the tricks mentioned here ( I have never had much luck w= ith short cuts). If it was my airplane I would pull the cyl. and fix the pr= oblem and not screw around with wobble test, staking the valve, or trying t= o 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 do= n't hone the cyl..=0A=C2=A0I have repaired/overhauled over a 1000 Continent= al and Lycoming cylinders and it does not take very long to R&R a cyl.=0ASw= aid Rahn=0AA&P,I.A.,ATP=0ALIVP-T(Walter)=0ALIVP-T(Garrett under constructio= n)=0A=0A=0A=C2=A0=0AOn Tue, Jan 24, 2012 at 11:06 AM, Dan & Kari Olsen=C2= =A0=C2=A0wrote:=0A=0ALML Gang,=0A>=C2=A0=0A>Doing the = annual on my 320 this week.=C2=A0 Compression check shows 77-78 on cylinder= s 1, 2, 4.=C2=A0 #3 is 75 and I hear pretty good leakage through the exhaus= t, indicating a leaking exhaust valve.=C2=A0 I=E2=80=99ve had no indication= of sticking valves or morning sickness.=C2=A0 I pulled the rocker cover an= d there is no abnormality there.=C2=A0 This engine is typically run lean of= peak at power settings of 55-65% power.=C2=A0 Oil changes every 25-35hrs.= =C2=A0 Engine has 623hrs since new.=0A>=C2=A0=0A>My question to those of yo= u who are much more experienced with the Lycoming 4-cylinder engines, is wh= at should be my next course of action?=0A>=C2=B7=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0Do the valve lapping procedure per the Lyc servi= ce instruction?=0A>=C2=B7=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0Start using TCP and re-check in a few hours?=0A>=C2=B7=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0Go run the engine hard and re-check = the compression?=0A>=C2=B7=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0Something else?=0A>=C2=A0=0A>I really want to nip this in the bud and= not end up with a burned exhaust valve, requiring pulling a jug.=0A>=C2=A0= =0A>Appreciate your thoughts and responses.=0A>=C2=A0=0A>Cheers!=C2=A0=0A>D= an Olsen --607277540-1731264335-1327671071=:60985 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Okay, I'll take the dare = from Swain and post what might be the more "normal" reply :-).  I thin= k he is being a little of a perfectionist.  I don't have his credentia= ls, but from what I have seen, a compression leakage of 74 to 76 is the mos= t common.  A compression number up to 78 suggests that the engine is p= umping excess oil past the rings and the oil is sealing that leak path. &nb= sp;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 h= ours 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 comp= ression 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 af= terward.  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 not a good thing ju= st before a compression test.  If I were really into the diagnostics I= would warm the engine (cowl off) at the normal runup rpm and then run it a= t 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? &nb= sp;With a modern engine and modern oil, I don't see any reason to change oi= l that often.  I would run it at least 50 hours and try to change it b= efore 75.  If the engine is run often, even 100 hours isn't out of line.  What does the oil look like at the oil change?  Can yo= u see the dipstick through the oil?  If so, it probably doesn't need t= o be changed yet.
Gary

Previously, from = Swain: 
&n= bsp;Remember one compression test is only a snapshot of what is happening i= n your engine. You need more than one and other information to develope a t= rend on what your engine is really doing.
 I would go f= ly your airplane at high power settings for one hour and come back and take another compression test. Then you might try some of th= e 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 a= round 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 Lycomi= ng cylinders and it does not take very long to R&R a cyl.
Swa= id 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 Ol= sen <olsen25@comcast.n= et> wrote:
LML Gang,
 
Doing the annual on my 320 this we= ek.  Compression check shows 77-78 on cylinders 1, 2, 4.  #3 is 7= 5 and I hear pretty good leakage through the exhaust, indicating a leaking = exhaust valve.  I=E2=80=99ve had no indication of sticking valves or m= orning sickness.  I pulled the rocker cover and there is no abnormalit= y 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.
 
<= span style=3D"font-family: Symbol; ">=C2=B7   &n= bsp;     Do the valve = lapping procedure per the Lyc service instruction?
=C2=B7       &n= bsp; Start using TCP and re-check in a few= hours?
=C2=B7 = ;        Go run the engine hard and re-check the compression?
<= div style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin= -left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padd= ing-left: 0px; display: block; line-height: normal; ">=C2=B7    =      Something else?
 
I reall= y want to nip this in the bud and not end up with a burned exhaust valve, r= equiring pulling a jug.
 
Appreciate your thoughts and responses.
 
Cheers!
&n= bsp;
Dan Olsen
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