X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 29 Jan 2012 17:16:11 -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 5367440 for lml@lancaironline.net; Fri, 27 Jan 2012 16:22:48 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.215.52; envelope-from=indigoaviation@gmail.com Received: by lagy4 with SMTP id y4so386878lag.25 for ; Fri, 27 Jan 2012 13:22:12 -0800 (PST) MIME-Version: 1.0 Received: by 10.152.114.74 with SMTP id je10mr4266331lab.40.1327699332389; Fri, 27 Jan 2012 13:22:12 -0800 (PST) Received: by 10.112.45.33 with HTTP; Fri, 27 Jan 2012 13:22:12 -0800 (PST) In-Reply-To: References: X-Original-Date: Fri, 27 Jan 2012 16:22:12 -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=f46d0408d7ed135aed04b78917b6 --f46d0408d7ed135aed04b78917b6 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Gary, My name is Swaid not Swain. You have some interesting procedures for the care and feeding of your engine. What data do you have to back up extending your oil change intervals? Is it that you just don't want to spend the money? Also all contaminates in oil are not black. There is also a calendar interval for oil change regardless of operating hours, it's to prevent corrosion inside the engine due to condensation. Also there is more to a compression test than just the number. There is a real neat place to get the right information on operating and maintenance of your engine. It's called the manufacturer. They have a vested interest in helping you get the best service from their product. Believe it or not they really know what they are talking about. Best of luck with your TBO, Swaid Rahn On Fri, Jan 27, 2012 at 1:40 PM, wrote: > ** > Grayhawks says high readings on a Lyc 320,360 may be OK based on the > tester orifice. Here's a bit of additional info: > > > > *FAASTeam Maintenance Safety Tip * > *November 2011* > > *Differential Compression Test (AC 43.13-1B)* > > The differential pressure tester is designed to check the compression of > aircraft engines by measuring the leakage through the cylinders caused by > worn or damaged components. > > The operation of the compression tester is based on the principle that, > for any given airflow through a fixed orifice, a constant pressure drop > across that orifice will result. The restrictor orifice dimensions in the > differential pressure tester should be sized for the particular engine as > follows: > > *(Although AC 43.13-1B was revised in 1998, the following information was > revised in Chg. 1 in September 2001. The identification criteria was > revised from using =93engines with a certain cubic inch displacement=94 t= o > cylinder bore)* > > *(1) *For an engine cylinder having less than a 5.00-inch bore; > 0.040-inch orifice diameter; > .250 inch long; and a 60-degree approach angle. > *(2) *For an engine cylinder with 5.00 inch bore and over: 0.060 inch > orifice diameter, .250 inch long, and a 60 degree approach angle. > > Remember, some of the smaller production engines have 5 inch or larger > cylinder bores (e.g. Lycoming O-320-A1A has a cylinder bore of 5.125 > inches). Therefore, an orifice of 0.060 diameter should be used to perfor= m > the compression test. > > See AC 43.13-1B= , > Chapter 8, paragraph 8-14 for more information. > ALSO at Sacramento Sky Ranch note that Lyc's are expected to result in > higher pressure readings - BUT orifice is not mentioned....... > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > In a message dated 1/27/2012 10:24:58 A.M. Central Standard Time, > casey.gary@yahoo.com writes: > > 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 --f46d0408d7ed135aed04b78917b6 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Gary,
My name is=A0=A0=A0=A0=A0=A0=A0 Swaid=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0 not=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0Swain.=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0 You have some interesting procedures for the care and fe= eding of your engine. What data do you have to back up extending your oil c= hange intervals? Is it that you just don't want to spend the money?
Also all contaminates in oil=A0are not black. There is also a calendar= interval for oil change regardless of operating hours, it's to prevent= corrosion inside the engine due to condensation.
=A0Also there is more to a compression test than just the number. Ther= e is a real neat place to get the right information on operating and mainte= nance of your engine. It's called the manufacturer. They have a vested = interest in helping you get the best service from=A0their product. Believe = it or not they really know what they are talking about.
=A0Best of luck with your TBO,
Swaid Rahn

On Fri, Jan 27, 2012 at 1:40 PM, <Sky2high@aol.com> = wrote:
Grayhawks says high readings on a Lyc 320,360 may be OK based on the t= ester orifice.=A0Here's a bit of additional info:
=A0
=A0=20

FAASTeam Ma= intenance Safety Tip
November 2011

Differential Compression Test (AC 43.13-1B)

The different= ial pressure tester is designed to check the compression of aircraft engine= s by measuring the leakage through the cylinders caused by worn or damaged = components.

The operation of the compression tester is based on the principle that, = for any given airflow through a fixed orifice, a constant pressure drop acr= oss that orifice will result. The restrictor orifice dimensions in the diff= erential pressure tester should be sized for the particular engine as follo= ws:

(Although AC 43.13-1B was revised in 1998, the following informa= tion was revised in Chg. 1 in September 2001. The identification criteria w= as revised from using =93engines with a certain cubic inch displacement=94 = to cylinder bore)

(1) For an engine cylinder having less than a 5.00-inch bore; 0.= 040-inch orifice diameter;
.250 inch long; and a 60-degree approach ang= le.
(2) For an engine cylinder with 5.00 inch bore and over: 0.0= 60 inch orifice diameter, .250 inch long, and a 60 degree approach angle. <= br>
Remember, some of the smaller production engines have 5 inch or larger = cylinder bores (e.g. Lycoming O-320-A1A has a cylinder bore of 5.125 inches= ). Therefore, an orifice of 0.060 diameter should be used to perform the co= mpression test.

See AC 43.13-1B, Chapter 8, paragraph 8-14 for more info= rmation.

ALSO at Sacramento Sky Ranch note that Lyc's are expected to resul= t in higher pressure readings - BUT orifice is not mentioned.......
=A0
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
In a message dated 1/27/2012 10:24:58 A.M. Central Standard Time, casey.gary@yahoo.com<= /a> writes:
Okay, I'll take the dare from Swain and post what might be the mor= e "normal" reply :-). =A0I think he is being a little of a perfec= tionist. =A0I don't have his credentials, but from what I have seen, a = compression leakage of 74 to 76 is the most common. =A0A compression number= up to 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 mo= re than 2 compression tests with ever-dropping values before I would even s= tart to worry. =A0That will take another 200 hours of operation. =A0I would= n't worry until the compression dropped below 70. =A0And like Dan said,= it is always a good idea to warm the engine and then do the compression te= st as soon as possible afterward. =A0I've gone as far as to warm the en= gine with the cowl off so I could do it faster, but to just idle on the gro= und is not a good thing just before a compression test. =A0If I were really= into the diagnostics I would warm the engine (cowl off) at the normal runu= p rpm and then run it at full power for maybe 15 seconds, pulling the mixtu= re while at full power to get a "clean" shut-off. =A0Then you'= ;ll get as good a test as possible.

And why do you change oil every 25-35 hours? =A0With a modern engine a= nd modern oil, I don't see any reason to change oil that often. =A0I wo= uld run it at least 50 hours and try to change it before 75. =A0If the engi= ne 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 differ from most here. It is based on 28 years as a= professional aircraft mechanic and a cylinder overhaul shop owner for 17 y= ears. 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 l= eak 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 l= ead to=A0 valve face breakage which might do major damage to one or more cy= l. 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. be= side it and lodge itself into the face of that piston while bending the oth= er 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 thr= ough the time it sits on it's valve seat to transfer heat from the valv= e to the head and also through the valve stem. That's why when guides g= et worn and seats leak you wear out valve stems and guides 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 happeni= ng in your engine. You need more than one and other information to develope= a trend on what your engine is really=A0doing.
=A0I would go fly your airplane at high power settings for one hour an= d come back and take another compression test. Then=A0you might=A0try some = of the tricks 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 sc= rew around with wobble test, staking the valve, or trying to lap a valve wi= thout 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..
=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 Rahn
A&P,I.A.,ATP
LIVP-T(Walter)
LIVP-T(Garrett 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 m= y 320 this week.=A0 Compression check shows 77-78 on cylinders 1, 2, 4.=A0 = #3 is 75 and I hear pretty good leakage through the exhaust, indicating a l= eaking exhaust valve.=A0 I=92ve had no indication of sticking valves or mor= ning sickness.=A0 I pulled the rocker cover and there is no abnormality the= re.=A0 This 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 with the Lycoming 4-cylinder engines, = is what should be my next course of action?
=B7=A0=A0=A0=A0=A0=A0=A0=A0=A0Do the valve lapping procedure per the Lyc service instruct= ion?
=B7=A0=A0=A0=A0=A0=A0=A0=A0=A0Start using TCP and re-check in a few hours?<= /div>
=B7=A0=A0=A0=A0=A0=A0=A0=A0=A0Go run the engine hard and re-check the compression?=
=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 pulli= ng a jug.
=A0
Appreciate your thoug= hts and responses.
=A0
Cheers!
=A0
Dan Olsen


--
Swaid L. Rahn
Indigo Aviation, Inc.
940 Mock Road
Springfi= eld, Ga. 31329
Cell 912.655.0966


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