Guy Prevost
Well Known Member
When I traded my beloved RV-8a for an RV-10, I knew I was accepting some risk. The 10 met my highest priorities—good airframe and light weight with a forward CG. The systems weren’t what I wanted, and I made the trade planning to upgrade them. I did that shortly after purchasing the plane. I knew there was risk of corrosion of the cam and lifters on this airplane since it lived next to the Chesapeake Bay and only flew 200 hours in the previous 8 years. In my risk matrix, pulling a cylinder is too invasive of a procedure without an apparent problem, so I chose to accept that risk. Sadly the financial portion of that risk was realized.
Over a year and 100 hours or so of flying, I monitored oil condition. Oil analysis came back nominal every time, but I always found a small amount of metal, both ferrous and non-ferrous in my oil filter. One cylinder had been replaced not long before I bought the plane and borescope images showed some corrosion in that one. I was hoping that was the source of the metal, but what I was finding wasn’t terribly consistent with that hope. This was particularly apparent after the problem showed up over several oil changes. Last March during a long flight home over the desert between China Lake and Albuquerque with both children on board, my wife and I decided it was time to dig deeper. Within a couple of weeks and with the help of my favorite mechanic I pulled the corroded #3 cylinder and looked. The cylinder was not too bad and sadly in this case, the rings and wrist pin end caps were in good shape. A look at the bottom end revealed the source of the metal. Several lifters were badly spalled and the cam showed associated wear.
Although I would rather have not had to deal with it I used this as an opportunity to make the airplane better. The engine only had 500 hours since a field overhaul. I briefly considered selling the engine as a core and buying a Thunderbolt engine from Lycoming. The engine deal from Van’s had not been used for this plane yet so it was in the realm of possibility. I also called a few engine shops and quickly wound up deciding to send my engine to Barrett Precision in Tulsa due to their impeccable reputation and the conversations I had with them over the phone. Rhonda at Barrett had a knock-down engine crate to me within a couple of days. It took a day or so to remove the engine and 30 minutes to assemble the crate around it. Barrett arranged the shipping both ways and it was a painless process.
Rhonda at Barret suggested not doing a complete overhaul but to do on IRAN on the engine with everything inspected to measure up to new limits. A full overhaul would have added much expense and little extra value. As a side note, every reputable engine shop I talked to recommended the same and I essentially wound up with an overhauled engine at 60% of the overhauled price. We replaced the cylinders with new Lycomings and installed 9:1 compression pistons. The cylinders went through Barrett’s standard port clean up to improve flow and all reciprocating parts were balanced. The oil pump, cam, and lifters were replaced and one bearing location on the crank was polished but not ground. Barrett’s standard process includes paint color of your choice on the case and proper treatment of the exterior of the cylinders for improved heat transfer. The engine isn’t painted after assembly, rather the cylinders are painted black with the heads left with a bare conversion coating. The case is masked and painted prior to assembly and all fasteners were inspected cleaned and sent out to have the CAD plaiting renewed. At my request intercylinder baffles were replaced. To my surprise, the edges of the new ones were already coated with RTV to prevent wear and improve air flow through the fins. I still had to fill the edge gaps though.
Over a year and 100 hours or so of flying, I monitored oil condition. Oil analysis came back nominal every time, but I always found a small amount of metal, both ferrous and non-ferrous in my oil filter. One cylinder had been replaced not long before I bought the plane and borescope images showed some corrosion in that one. I was hoping that was the source of the metal, but what I was finding wasn’t terribly consistent with that hope. This was particularly apparent after the problem showed up over several oil changes. Last March during a long flight home over the desert between China Lake and Albuquerque with both children on board, my wife and I decided it was time to dig deeper. Within a couple of weeks and with the help of my favorite mechanic I pulled the corroded #3 cylinder and looked. The cylinder was not too bad and sadly in this case, the rings and wrist pin end caps were in good shape. A look at the bottom end revealed the source of the metal. Several lifters were badly spalled and the cam showed associated wear.
Although I would rather have not had to deal with it I used this as an opportunity to make the airplane better. The engine only had 500 hours since a field overhaul. I briefly considered selling the engine as a core and buying a Thunderbolt engine from Lycoming. The engine deal from Van’s had not been used for this plane yet so it was in the realm of possibility. I also called a few engine shops and quickly wound up deciding to send my engine to Barrett Precision in Tulsa due to their impeccable reputation and the conversations I had with them over the phone. Rhonda at Barrett had a knock-down engine crate to me within a couple of days. It took a day or so to remove the engine and 30 minutes to assemble the crate around it. Barrett arranged the shipping both ways and it was a painless process.
Rhonda at Barret suggested not doing a complete overhaul but to do on IRAN on the engine with everything inspected to measure up to new limits. A full overhaul would have added much expense and little extra value. As a side note, every reputable engine shop I talked to recommended the same and I essentially wound up with an overhauled engine at 60% of the overhauled price. We replaced the cylinders with new Lycomings and installed 9:1 compression pistons. The cylinders went through Barrett’s standard port clean up to improve flow and all reciprocating parts were balanced. The oil pump, cam, and lifters were replaced and one bearing location on the crank was polished but not ground. Barrett’s standard process includes paint color of your choice on the case and proper treatment of the exterior of the cylinders for improved heat transfer. The engine isn’t painted after assembly, rather the cylinders are painted black with the heads left with a bare conversion coating. The case is masked and painted prior to assembly and all fasteners were inspected cleaned and sent out to have the CAD plaiting renewed. At my request intercylinder baffles were replaced. To my surprise, the edges of the new ones were already coated with RTV to prevent wear and improve air flow through the fins. I still had to fill the edge gaps though.
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