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teamgrumman(at)yahoo.com
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 Posted: Tue Nov 09, 2010 6:47 pm Post subject: Cylinder woes |
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[Barry] - When you say 30% less surface area. How is that calculated, 30% less fin count or smaller fins?
I wonder how much cooling was gained since the fins were NOT painted?
The cast fins are not smooth. The roughness adds surface area. Machines fins have less area.
From: FLYaDIVE <flyadive(at)gmail.com>
To: teamgrumman-list(at)matronics.com
Sent: Tue, November 9, 2010 4:03:39 PM
Subject: Re: Cylinder woes
Hi Gary:
I'm not discriminatory. I dislike ALL of Lycoming  Cylinders, Gears, Crankshafts and Cams.
I have embedded my other response within the body of your email
On Tue, Nov 9, 2010 at 1:33 PM, Gary Vogt <teamgrumman(at)yahoo.com (teamgrumman(at)yahoo.com)> wrote:
| Quote: | Well, Barry,
What are we talking about here? Gears? or Cylinders?
As for the gears, how many out right failures where there? Not many.
|
[Barry] - I agree 100% with you NOT MANY. That is my point. There was NO reason to force a replacement. The ONLY gears that SHOULD have been replace AT Lycoming's expense should have been the sintered gears.
| Quote: | For the most part, the bottom end of any Lycoming engine will run seemingly forever with a bad cam, bent rods, and a crank that needs to be turned. IF the engine has been taken care of regarding oil changes and regular use, the bottom end is good for 4000 hours.
Rockers: Here, I'd have to agree 100%. Two nearly identical rockers with no stamping showing how they go in. In 1984, I was doing a very thorough annual on my first Cheetah. The engine had 600 hours on it since new. The rocker cover gaskets were leaking, so, I decided to change them. In the process, with a brand new Lycoming overhaul manual in hand, I decided to do a dry tappet clearance check, just for shits-n-grins. Inside the maintenance hangar, about 20 yards from the main FBO, I started carefully removing all the parts. On the work bench, I laid out everything in the order I removed them. During the cleaning process, I noticed a there was a difference between the rockers. Strange this was, from the factory, one side of the engine was one way, the other side was different. I asked the mechanic there, Jack, a guy who had been working on planes for some 30 years, which was which. He said, and I quote, "I don't know. I've never noticed a difference before." I called Lycoming and talked to an engineer. He didn't know either. Several transfers later, I got an answer.
Do you know the logic behind the different rockers? The squirter is supposed to squirt oil on the valve stem . . . exhaust only to help cool the valve. The other one is supposed to dribble oil onto the rocker . . . . intake only. These engines have no oil seal on the valve stems. Squirting oil on the intake only makes oil go into the intake port, coat the inside with residue, and burn more oil.
|
[Barry] - Yes, I am very familiar with how to determine which rocker goes where. The way you describe the the NO SEAL condition on the valve stem is what I was thinking about... My thought process was:
If the oil squirted on the stem BURNS and COKES the stem must be HOT.
So, if I could lower the temps of the valve stem I would not get burning and coking. The MORE oil to the head would lower those temps.
The idea seems to fit the logic BUT I have no real numbers to work with.
As I mentioned I did replace ALL the rockers with Exhaust Rockers. And I understand Lycoming has done the same thing. Makes sense as it would also reduce inventory and chance of mix-up.
| Quote: |
Waiting for more oil to be delivered to the heads: This is a major misconception. Born, in part, by Bill Scott and Bill Marvel. Sodium filled valves were first used almost 100 years ago. By the mid 30's there was a lot of research being done on sodium filled valves. Why? Because, at the time, rockers were out in the open. Sodium filled valves offered a way to shed heat without much oil. In fact, research done by Samuel Heron in the late teens, early 20s, showed that excess oil on the valve causes valve sticking. And, if you think that sticking valves are unique to Lycomings, you haven't kept up on the valve problems (using solid valves and lots of oil) in Continental engines. Do a little research regarding oil on sodium filled valves. The problem is really due to the geometry of the rocker/valve stem during operation. The side loads on the valve cause the guide to be worn excessively*. This is true of ALL engines without roller rockers. In this respect, the solid lifter engines (i.e., O235) are better. Ideally, you want to get roller rockers to get rid of the side loads. Hot Rod magazine had an excellent article on valve geometry not long ago.
* this is THE reason why I recommend a top overhaul with new cylinders at 1000 hrs. I've pulled a lot of cylinders with 1000 to 1500 hours on them. I send them to Ken for tear down and inspection. I pay for the research on this one. In every case, the cylinders have cracks in the exhaust port. Most, but not all, show excess wear in the guides. The ones that don't show no correlation between them. (that is, without getting Charlie Epps to do a math analysis of it.) It just isn't worth patching the cylinder to get another 1000 hours out of it. It'll never make it.
|
[Barry] - Gary, I am lacking experience of the ages in this area (You Old Fart ). You have posted a few times that you see cylinders with 1000 to 1500 Hours on them. The limited experience I have in this area and ONLY from reading Logbooks is cylinders usually last 500 to 600 Hours, before a Top is required.
I know there are thousands of reasons why, but... Is there any advice or information you can offer to reach 1000 Hours?
| Quote: |
Fins on Superior engines: Now, I ask, was that a work of art or what? Really pretty weren't they. Problem was, those machined heads (in place of cast heads) gave up 30% of the surface area needed to shed heat.
|
[Barry] - When you say 30% less surface area. How is that calculated, 30% less fin count or smaller fins?
I wonder how much cooling was gained since the fins were NOT painted?
| Quote: |
Casting flashings: I ground out the flashings on about a half dozen engines. All with JPI engine analyzers. No change. Sloppy workmanship, for sure, but not critical. The new heads are a whole lot better.
|
[Barry] - You may have seen one of my posts from years back and recently re-posted about an RV6 that I did a fin clean-up on. We saw 40 F drop in CHT. The CHT instrument is a Grand Rapids with screw in probes. This in no way is what I expected or would cal typical. Of course temperature is a fleeting thing and OAT has an effect but CHT's now do NOT go above 400 F.
Later Gary,
Barry
[quote][b]
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teamgrumman(at)yahoo.com
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| Posted: Tue Nov 09, 2010 6:49 pm Post subject: Cylinder woes |
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[Barry] - Yes, I am very familiar with how to determine which rocker goes where. The way you describe the the NO SEAL condition on the valve stem is what I was thinking about... My thought process was:
If the oil squirted on the stem BURNS and COKES the stem must be HOT.
So, if I could lower the temps of the valve stem I would not get burning and coking. The MORE oil to the head would lower those temps.
If you have too much, you will have excess coking and sucking oil into the intake.
From: FLYaDIVE <flyadive(at)gmail.com>
To: teamgrumman-list(at)matronics.com
Sent: Tue, November 9, 2010 4:03:39 PM
Subject: Re: Cylinder woes
Hi Gary:
I'm not discriminatory. I dislike ALL of Lycoming Cylinders, Gears, Crankshafts and Cams.
I have embedded my other response within the body of your email
On Tue, Nov 9, 2010 at 1:33 PM, Gary Vogt <teamgrumman(at)yahoo.com (teamgrumman(at)yahoo.com)> wrote:
| Quote: | Well, Barry,
What are we talking about here? Gears? or Cylinders?
As for the gears, how many out right failures where there? Not many.
|
[Barry] - I agree 100% with you NOT MANY. That is my point. There was NO reason to force a replacement. The ONLY gears that SHOULD have been replace AT Lycoming's expense should have been the sintered gears.
| Quote: | For the most part, the bottom end of any Lycoming engine will run seemingly forever with a bad cam, bent rods, and a crank that needs to be turned. IF the engine has been taken care of regarding oil changes and regular use, the bottom end is good for 4000 hours.
Rockers: Here, I'd have to agree 100%. Two nearly identical rockers with no stamping showing how they go in. In 1984, I was doing a very thorough annual on my first Cheetah. The engine had 600 hours on it since new. The rocker cover gaskets were leaking, so, I decided to change them. In the process, with a brand new Lycoming overhaul manual in hand, I decided to do a dry tappet clearance check, just for shits-n-grins. Inside the maintenance hangar, about 20 yards from the main FBO, I started carefully removing all the parts. On the work bench, I laid out everything in the order I removed them. During the cleaning process, I noticed a there was a difference between the rockers. Strange this was, from the factory, one side of the engine was one way, the other side was different. I asked the mechanic there, Jack, a guy who had been working on planes for some 30 years, which was which. He said, and I quote, "I don't know. I've never noticed a difference before." I called Lycoming and talked to an engineer. He didn't know either. Several transfers later, I got an answer.
Do you know the logic behind the different rockers? The squirter is supposed to squirt oil on the valve stem . . . exhaust only to help cool the valve. The other one is supposed to dribble oil onto the rocker . . . . intake only. These engines have no oil seal on the valve stems. Squirting oil on the intake only makes oil go into the intake port, coat the inside with residue, and burn more oil.
|
[Barry] - Yes, I am very familiar with how to determine which rocker goes where. The way you describe the the NO SEAL condition on the valve stem is what I was thinking about... My thought process was:
If the oil squirted on the stem BURNS and COKES the stem must be HOT.
So, if I could lower the temps of the valve stem I would not get burning and coking. The MORE oil to the head would lower those temps.
The idea seems to fit the logic BUT I have no real numbers to work with.
As I mentioned I did replace ALL the rockers with Exhaust Rockers. And I understand Lycoming has done the same thing. Makes sense as it would also reduce inventory and chance of mix-up.
| Quote: |
Waiting for more oil to be delivered to the heads: This is a major misconception. Born, in part, by Bill Scott and Bill Marvel. Sodium filled valves were first used almost 100 years ago. By the mid 30's there was a lot of research being done on sodium filled valves. Why? Because, at the time, rockers were out in the open. Sodium filled valves offered a way to shed heat without much oil. In fact, research done by Samuel Heron in the late teens, early 20s, showed that excess oil on the valve causes valve sticking. And, if you think that sticking valves are unique to Lycomings, you haven't kept up on the valve problems (using solid valves and lots of oil) in Continental engines. Do a little research regarding oil on sodium filled valves. The problem is really due to the geometry of the rocker/valve stem during operation. The side loads on the valve cause the guide to be worn excessively*. This is true of ALL engines without roller rockers. In this respect, the solid lifter engines (i.e., O235) are better. Ideally, you want to get roller rockers to get rid of the side loads. Hot Rod magazine had an excellent article on valve geometry not long ago.
* this is THE reason why I recommend a top overhaul with new cylinders at 1000 hrs. I've pulled a lot of cylinders with 1000 to 1500 hours on them. I send them to Ken for tear down and inspection. I pay for the research on this one. In every case, the cylinders have cracks in the exhaust port. Most, but not all, show excess wear in the guides. The ones that don't show no correlation between them. (that is, without getting Charlie Epps to do a math analysis of it.) It just isn't worth patching the cylinder to get another 1000 hours out of it. It'll never make it.
|
[Barry] - Gary, I am lacking experience of the ages in this area (You Old Fart ). You have posted a few times that you see cylinders with 1000 to 1500 Hours on them. The limited experience I have in this area and ONLY from reading Logbooks is cylinders usually last 500 to 600 Hours, before a Top is required.
I know there are thousands of reasons why, but... Is there any advice or information you can offer to reach 1000 Hours?
| Quote: |
Fins on Superior engines: Now, I ask, was that a work of art or what? Really pretty weren't they. Problem was, those machined heads (in place of cast heads) gave up 30% of the surface area needed to shed heat.
|
[Barry] - When you say 30% less surface area. How is that calculated, 30% less fin count or smaller fins?
I wonder how much cooling was gained since the fins were NOT painted?
| Quote: |
Casting flashings: I ground out the flashings on about a half dozen engines. All with JPI engine analyzers. No change. Sloppy workmanship, for sure, but not critical. The new heads are a whole lot better.
|
[Barry] - You may have seen one of my posts from years back and recently re-posted about an RV6 that I did a fin clean-up on. We saw 40 F drop in CHT. The CHT instrument is a Grand Rapids with screw in probes. This in no way is what I expected or would cal typical. Of course temperature is a fleeting thing and OAT has an effect but CHT's now do NOT go above 400 F.
Later Gary,
Barry
[quote][b]
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?TeamGrumman-List |
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teamgrumman(at)yahoo.com
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| Posted: Tue Nov 09, 2010 6:55 pm Post subject: Cylinder woes |
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I had a plane come in that was covered with oil. I took off everything that could come off and started cleaning everything. All of the oil drain back hoses were AFU. A couple drain back tubes were leaking at the fitting. The oil pan/sump was leaking. The rockers were leaking. The push rod tubes and the cylinders were leaking.
• replaced the hoses and drain back tube fitting on the cylinders.
• replaced the "O" rings on the cylinders
• replaced the push rod tube seals.
• replaced the rocker cover gaskets.
• when I got to the sump, I noticed that part of the original gasket was still on the sump. Whoever overhauled the engine, paid no attention to sealing it.
The engine had 120 hours on it since major overhaul.
From: FLYaDIVE <flyadive(at)gmail.com>
To: teamgrumman-list(at)matronics.com
Sent: Tue, November 9, 2010 4:12:43 PM
Subject: Re: TeamGrumman-List: Cylinder woes
WOW ! ! !
Gary,
That crack is impressive.
A dirty engine would surely hide that very easily.
HMmmmmmm, I'm working on finding an oil leak on an AA-1 with an O-320. You just gave me another location to look at.
And GUAD! Trying to find a leak on a dirty engine is like trying to find Georgia Mud on a South Carolina pig.
Barry
[quote][b]
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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