This exhaust valve in a turbo-normalized A36 Bonanza looks quite good. The appearance is mostly concentric and uniform. There’s just that one area at about the 10 to 11 o’clock position that looks slightly uneven.

If the compression test had been good, I likely would not have lapped the valve.

But since it was 44/80 when the required minimum was 46/80 according to the master orifice reading, I lapped the valve in place, installed a new rotocoil and new valve springs, and put it back together.

Amazingly, after doing this work, I got a good solid cold compression of 65/80!

I’ve found that lapping the exhaust valve and restoring a good seal between the edge of the valve and the seat is the most effective way to improve a low compression number, as long as everything else looks good in the cylinder.

Here are some additional photos of the seat area before lapping:

You can listen to the full story in the audio for this episode.

I’ve also included some email feedback from the last episode, including a story about an airplane that made a precautionary landing in a field!

Here’s a totally separate photo of that same airplane from one of its scenic flights:

Thanks Justin, for agreeing to let me share your amazing story of landing this airplane in a field!

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