Gyropilot007
04-17-2006, 09:57 AM
My Friends:
I learned a very valuable lesson this weekend, one that I feel obligated to share with all of my friends in the gyro community.
As many of you know, I own an RAF-2000. My gyro originally was equipped with a 2.2 liter Subaru engine direct from the RAF factory. But once I began to fly my bird I soon realized that a 2.2 wasn't going to cut hauling my 275 lb frame around along with a passenger. The performance was terrible.
Thus began my search for a suitable 2.5 Subaru replacement engine. My first thought was to contact RAF. They were asking over $10,000 for a rebuilt 2.5 liter engine. I decided to look elsewhere.
At this point I should note that my background is electrical and computer engineering. I'm not in any way an expert mechanic.
So, I began a search for an engine on the Internet. After a fair amount of searching I came across an engine being sold my Larry Martin. I was familiar with Larry because I had purchased my horizontal stabilizer and my overhead console from him. I had spoken with him on the phone many times before.
The engine Larry had for sale was a Subaru 2.5 liter with the Delta cam grind. This meant that the engine should be putting out close to 200 hp!!! Just what I was looking for!!!
I called Larry to discuss the engine. He assured me that it was in GREAT shape and would be a direct replacement for my current 2.2. He did say that the engine had a custom, low profile intake manifold but that that should present no problem.
Based on Larry's assurances I agreed to purchase the engine. I live in NW Indiana and as it turned out, Larry was planning to drive up to Indiana to attend the annual auto auction in Auburn. I agreed to meet Larry there to pick-up the engine. When we met, and I saw the engine, I again asked him if he was sure it would fit in an RAF as it was. Larry had built two RAF's before so I valued his opinion. He said he was sure that it would.
Well, once I got the engine back to my hangar and compared with my 2.2 it was obvious that the engine wouldn't work. The low profile intake did not have enough room to fit the throttle body or the air filter. I had to source a new stock RAF 2.5 liter intake manifold.
Once I did this and made some other modifications I was able to install the engine. Since I am not an expert mechanic by any means, I decided to have an expert look over the engine. I have an hangar at the Valparaiso airport and fortunately there is a very good aircraft maintenance facility on the field. They have experience with auto engines modified for aircraft use.
I had them give the engine a complete checkout. They said the engine looked to be in very good shape from what they could tell without completely disassembling the unit. They did recommend that after I had about 5 hours on the engine they cut open the oil filter for a check. They said this is one of the best tests you can do to determine the health of an engine.
Well, I flew five hours on the engine and then they cut the filter. There were some small metal shavings, some carbon particles and what appeared to be some silicone in the filter. They then flushed the engine with an engine solvent and put in new oil. I then flew it for another five hours.
We performed another cut filter test. Once again there were particles in the oil but not as much. The decision was made to fly a few more hours and check again.
So I few again for about 3 hours. We cut the filter and there were more particles that before. We decided that it was unsafe to fly this engine any longer until we got to the bottom of the problem.
So, last week the engine was removed from the gyro and totallly dismantled. The problem was discovered.
Then engine was obviously dismantled by the prior owner when the custom cams were installed. When the engine was reassembled a liquid silicone gasket material was used. The person using it applied about 10 times as much as was needed. The net result was the the silcone squeezed into the engine. There was silicone everywhere. The oil sump filter was clogged with it. Even though I had good old pressure the actual flow was greatly reduced. This starved the pistons of oil and the lower rings overheated and froze. They then began scraping the cylinder walls. This where the metal pieces found in the oil filter originated. The carbon flakes were from the underside of the pistons where the oil was being cooked due to the low flow.
I am very lucky that I was performing the oil filter inspection and that I listened to a knowledgeable mechanic. The engine would not have lasted much longer under these conditions.
Fortunately the engine is still in very good shape. The cylinder walls will have to be honed and the pistons will be replaced. Some scoring on the crankshaft due to the metal particles will have to been fixed and the bearings replaced. But the net result will be that in the end I will have a practically new engine.
Explaination of the Pictures
The first picture is the oil pump sump tube screen. You can see it is half blocked this picture but most of the debris had already fallen off when this picture was taken.
The second picture shows some of the silicone "ropes" found inside the engine. There were quite a few of these found.
The third picture shows one of pistons. You can see that it overheated on the bottom side. The bottom row of rings are frozen in place.
The last picture is one of the crankshaft bearings. It was damaged by some of the metal particles that were suspended in the oil.
I have learned a valuable lesson here and I thought I would share it all with you.
Best regards,
Bob
I learned a very valuable lesson this weekend, one that I feel obligated to share with all of my friends in the gyro community.
As many of you know, I own an RAF-2000. My gyro originally was equipped with a 2.2 liter Subaru engine direct from the RAF factory. But once I began to fly my bird I soon realized that a 2.2 wasn't going to cut hauling my 275 lb frame around along with a passenger. The performance was terrible.
Thus began my search for a suitable 2.5 Subaru replacement engine. My first thought was to contact RAF. They were asking over $10,000 for a rebuilt 2.5 liter engine. I decided to look elsewhere.
At this point I should note that my background is electrical and computer engineering. I'm not in any way an expert mechanic.
So, I began a search for an engine on the Internet. After a fair amount of searching I came across an engine being sold my Larry Martin. I was familiar with Larry because I had purchased my horizontal stabilizer and my overhead console from him. I had spoken with him on the phone many times before.
The engine Larry had for sale was a Subaru 2.5 liter with the Delta cam grind. This meant that the engine should be putting out close to 200 hp!!! Just what I was looking for!!!
I called Larry to discuss the engine. He assured me that it was in GREAT shape and would be a direct replacement for my current 2.2. He did say that the engine had a custom, low profile intake manifold but that that should present no problem.
Based on Larry's assurances I agreed to purchase the engine. I live in NW Indiana and as it turned out, Larry was planning to drive up to Indiana to attend the annual auto auction in Auburn. I agreed to meet Larry there to pick-up the engine. When we met, and I saw the engine, I again asked him if he was sure it would fit in an RAF as it was. Larry had built two RAF's before so I valued his opinion. He said he was sure that it would.
Well, once I got the engine back to my hangar and compared with my 2.2 it was obvious that the engine wouldn't work. The low profile intake did not have enough room to fit the throttle body or the air filter. I had to source a new stock RAF 2.5 liter intake manifold.
Once I did this and made some other modifications I was able to install the engine. Since I am not an expert mechanic by any means, I decided to have an expert look over the engine. I have an hangar at the Valparaiso airport and fortunately there is a very good aircraft maintenance facility on the field. They have experience with auto engines modified for aircraft use.
I had them give the engine a complete checkout. They said the engine looked to be in very good shape from what they could tell without completely disassembling the unit. They did recommend that after I had about 5 hours on the engine they cut open the oil filter for a check. They said this is one of the best tests you can do to determine the health of an engine.
Well, I flew five hours on the engine and then they cut the filter. There were some small metal shavings, some carbon particles and what appeared to be some silicone in the filter. They then flushed the engine with an engine solvent and put in new oil. I then flew it for another five hours.
We performed another cut filter test. Once again there were particles in the oil but not as much. The decision was made to fly a few more hours and check again.
So I few again for about 3 hours. We cut the filter and there were more particles that before. We decided that it was unsafe to fly this engine any longer until we got to the bottom of the problem.
So, last week the engine was removed from the gyro and totallly dismantled. The problem was discovered.
Then engine was obviously dismantled by the prior owner when the custom cams were installed. When the engine was reassembled a liquid silicone gasket material was used. The person using it applied about 10 times as much as was needed. The net result was the the silcone squeezed into the engine. There was silicone everywhere. The oil sump filter was clogged with it. Even though I had good old pressure the actual flow was greatly reduced. This starved the pistons of oil and the lower rings overheated and froze. They then began scraping the cylinder walls. This where the metal pieces found in the oil filter originated. The carbon flakes were from the underside of the pistons where the oil was being cooked due to the low flow.
I am very lucky that I was performing the oil filter inspection and that I listened to a knowledgeable mechanic. The engine would not have lasted much longer under these conditions.
Fortunately the engine is still in very good shape. The cylinder walls will have to be honed and the pistons will be replaced. Some scoring on the crankshaft due to the metal particles will have to been fixed and the bearings replaced. But the net result will be that in the end I will have a practically new engine.
Explaination of the Pictures
The first picture is the oil pump sump tube screen. You can see it is half blocked this picture but most of the debris had already fallen off when this picture was taken.
The second picture shows some of the silicone "ropes" found inside the engine. There were quite a few of these found.
The third picture shows one of pistons. You can see that it overheated on the bottom side. The bottom row of rings are frozen in place.
The last picture is one of the crankshaft bearings. It was damaged by some of the metal particles that were suspended in the oil.
I have learned a valuable lesson here and I thought I would share it all with you.
Best regards,
Bob