A Story About Engine Corrosion and Ugly Cowlings

[Guy Prevost]

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.

[Guy Prevost]

With the plane out of service I decided to repair the cowling. The original fiberglass work was poor, the fit was poor, paint adhesion was poor, and the builder had riveted aluminum strips down the side to support camlock receptacles. The rivets were visible and working loose. To compound the problem, I had to slide the cowling aft a bit to clear the spinner plate when I made the switch to a Whirlwind prop last year. Time to make it right. I was so embarrassed by this at Oshkosh 2016 that I kept the plane covered. Before I removed the engine I aligned the cowling carefully, and mapped out the path forward with tape, notes and photos.









While the engine was at Barrett I slowly built up the cowling edges, reinforced old camlock holes, and replaced the metal camlock strips down the sides with fiberglass a-la a Dan Horton post on here somewhere. Real life kicked in and I got sent to the Pacific for a couple of months for the day job. The engine took some what longer than expected, but communication was good and it arrived back in Albuquerque the same day I did.

I got the engine re-installed, test fit the cowling and started paint prep.





This was my first time shooting base clear instead of single stage. Each offers advantages, but base clear is a clear winner when dealing with metallic paint. I didn’t want to transport the plane or to spray paint at the airport, so I knew I wouldn’t get a perfect match from the cowling to the fuselage. The color matching came out better than expected, but he upper, light silver is a little more blue than on the rest of the plane. It looks better to the eye than the camera. I used to build cabinets and furniture for a living, painted my first RV, and have done some car projects so this isn’t my first time with a spray gun. Still, it always amazes me that it takes a day to paint a month’s worth of preparation.

[Guy Prevost]

Somewhere in there, I got my BFR done in a friend’s C-170 (I’m tailwheel current again!), got the condition inspection done, and the airplane assembled with my little helpers. My two year old helped with the upholstery and the video below is of my 4 year old boy installing the baggage floors. He installed all the screws with a power screwdriver without stripping a single screw head. I’m a proud dad!



Kid Video: https://photos.smugmug.com/Airplanes..._7630-1280.mp4

The test flight was wonderfully uneventful. The first hour on the engine was in Barrett’s test cell. I ran it 5 minutes on the ground before cowling up and then I flew it a few days later. My field elevation is 5800 feet so a cool morning and flying down the river valley at 6500’ was my best course for break in. It also puts me over some of the only agricultural fields in New Mexico. I Flew 3 hours down the valley, Rich of Peak and burning an appalling 17 gph at 75% power. Peak CHTs started at about 400 and dropped from there. I normally fly much higher and LOP, but I’m pretty excited to see 180+KTAS in level flight in this regime. I filled up with cheap gas and made an uneventful 15 minute flight home. The photo below is shortly after levelling off. The CHTs dropped about 20 degrees from here over the course of the flight. They’re still considerably higher than I was seeing before, but it’s not an apples-to-apples comparison since I seldom get the opportunity to cruise at 75% power and the engine isn’t broken in yet. I’ll repeat this flight one more time after an inspection, and then clear the airplane for my wife to fly and for passengers.



Serious test pilot face.



All told the airplane was down just shy of 7 months. It’s the longest I’ve been without an RV to fly since 2008. I now have an airplane I’m exceedingly happy with. It meant re-doing everything but the airframe over a span of 20 months, but in general I had a plane to fly during that period. It may have made more sense to build this one myself too, but the finances and timing worked better for us this way since we didn’t want to have a longer period without an airplane.

[sblack]

We need a pic of the finished product! That engine looks really nice. My engine builder rattle canned the whole engine - fasteners and all. I hate that, and it is bad for heat transfer on the jugs. I have a mind to get out the tooth brush and scrub it all off. Yours looks like a show piece and I bet it runs real smooth. I think I will send my next engine to Barrett.

[vic syracuse]

Nice job! Barrett does a really nice job with the IRAN. It is the right way to go for piece of mind without breaking the bank.

Vic

[Guy Prevost]

Originally Posted by sblack

We need a pic of the finished product! That engine looks really nice. My engine builder rattle canned the whole engine - fasteners and all. I hate that, and it is bad for heat transfer on the jugs. I have a mind to get out the tooth brush and scrub it all off. Yours looks like a show piece and I bet it runs real smooth. I think I will send my next engine to Barrett.

Scott,
Here's a photo of the nearly complete engine install and of the finished product.

[KRviator]

This simple photo just made my day!

Tomorrow I am planning to (finally, after 18 months) be painting the wheel pants and I was umming and ahhing how to do the desired yellow horizontal stripe. This single photo explains it perfectly. Thanks!