Van's RV-9A in Aurora

The Big Picture

The Big Picture
Flying! 8/28/2011

Sunday, May 15, 2016

Engine Woes

Annual on the RV

Started knocking tasks out in February. If the weather is crappy, might as well work on the airplane since it has to be done anyway. With an El Nino year, it never got too cold, but we had a lot of clouds starting in February.

Finally got to the end of the list at the end of March, and was trying to get it ready for an upcoming formation clinic. The last item to take care of was some TLC for the #2 exhaust valve, which had been showing signs of morning sickness. It hadn't been a problem since November, but starting the engine up for the oil change, and for the compression check it was back.

Sure enough. Compressions were 74, 20, 79, 79. That unfortunately is not a typo. #2 was stuck open for the check, and it was hissing at the exhaust pipe. I knew from the EGT gauges it was #2, but this proved it also.

So I arranged for the local Spicewood mechanic, Chris Albrecht, to help work on the valve.

It took a lot of effort to get the valve punched through, and he was commenting the whole time that this was unusual. Once the valve was through, a quick look at the guide with a borescope revealed problems. He suggested pulling the cylinder for rework.

So off comes #2.

With the cylinder off, it is possible to see some cam lobes. After 500 hours, they were starting to show signs of distress. I had not seen any metal in the filter, and the oil analysis was normal and steady for all of the past samples (including the one I eventually got back from the oil change at annual).

But with the cam starting to degrade, he suggested a tear down. This was probably to drastic, I think Mike Busch would have said so, and I know that Seth though so. But we started working on it.

This is an image of the forward crankshaft journal from the Magnetic Particle Inspection (aka magnaflux). The circle is the main oil journal that collects oil for pressurizing a constant speed prop. The two tiny white streaks emanating from the left half of the oil journal show that my crank suffered a prop strike in the past. My prop is in perfect condition, so this was like this when I bought the engine. As a result, I had to find another crankshaft. This only cost $3200. I hope to sell this crank for use in an airboat. It should be fine for that application.