Two engine failures, same plane, same engine.
This happened in the mid nineties with my RV4. There was no internet to speak of and certainly no type forums. All information came from the plans and other RV builders in southern Ontario, Canada. It would have been impossible to build without their help, Gord Baxter, Rick West, Charlie Douma, as great examples of help.
Anyways at the time there were not a lot of RVs and engines being so expensive there was a guy who worked at a licensed shop that built up engines at his home in his spare time. Engines were reported to have all new or rebuilt parts to spec.
My first failure was with the fuel servo. On run up the engine was a bit rough at idle but I "knew" it would clear up with full power. Well it did clear up at full power but the problem was that it would not run rpms less than 2000rpms. There is no way you are going to land a RV4 with a fixed pitch prop at 2000rpms.
I did a few circuits at altitudes and decided to cut power at base a little higher then normal. I expected, and planned on being at the far end of a 5000' runway when stopped. The interesting thing is that a fixed pitch prop, when running, pulls a lot more then one would think and so without it I landed save, but much shorter than I would have thought.
The Bendix servo was removed and sent back to engine builder. He had bought it with the understanding that it had been rebuilt. This was not the case. I had to send it to a real licensed shop, at my expense to get it rebuilt. It was in terrible shape, a real case of fraud.
Anyways I bit the bullet and it ran beautifully after that. It is nice to have an airport close when the fan stops.
The next failure happened with the same plane and engine. This time I was five miles from the airport going very fast, 2900 rpm, wound out. I had been told many times that higher rpms were fine. I guess was a slow learner!
One big bang and things got quiet, 3000' and I could see the airport. I passed over a nice big paved road, that was not busy, as I thought I would get to the airport. I did not. As it turns out I live 1.5NM north of the airport and I have four hundred acres. No runway at the time but I was very familiar with the fields. I set it down in a recently planted soybean field the same direction as the rows of plants.
Heck the RV4 wheel base fits down a 15" row!
Anyways after the initial shock wore off I towed the plane back to my barn and started looking for reasons.
I dropped an intake valve. When this happens it rattles around in the affected cylinder and as it is the intake valve it starts to pump air into the other cylinders completely destroying any chance of running on three cylinders.
The engine builder rebuilt the engine, with all new parts. I paid for parts, he supplied labour.
At the time was building my first HR2 and it was at the fuselage stage and to me it looked a bit like a coffin. I gave some serious consideration into looking for another hobby.
However a decision was made from that time forward, to only deal with actual legitimate engine shops. 2000 hours and 25 years later I have not had any engine stoppages with the next ten airplanes that I have built and flown.
I do, however, go out of my way to not fly over large bodies of water, to try to always have a road in sight and to fly as high as I can. Altitude is your friend.