157 – Valve lapping, shock mounts, and vacuum issues

Airplane Owner Maintenance - By Dean Showalter

Valve lapping is sometimes a great option for improving cylinder compression and extending the life of an exhaust valve. We’ll talk about it in today’s episode.

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In today’s episode, we have three issues from Trace’s Cessna 310 this past week:

1. Lapping an exhaust valve.
2. Repositioning and correctly installing an engine shock mount.
3. Evaluating a vacuum system issue, and making a plan.

First, the lapping project. At the recent annual inspection, the compression in the right engine cylinder #4 was in the mid-50’s. After lapping we got a solid 64/80, a significant improvement.

Second, one engine shock mount was out of position:

The 1/4 inch gap got my attention and we had to hoist the engine and loosen the bolt to install the lower shock mount correctly. Here’s the result – notice the 1/4 inch gap has been closed.

The third isssue showed up when we ran the engines. Notice the oil pressure gauges… only the left engine is running. But the vacuum gauge indicates both vacuum pumps are operating.

This usually indicates a problem with the vacuum manifold valve. Most likely, it will need to be replaced.

After we checked and verified there were no oil leaks, Trace took me for a ride in his Cessna 310… a great experience! Thank you Trace!

Trace has been a Navy F-18 test pilot for quite a few years, and it was awesome to fly with him!

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And to wrap us this episode, I also met Tobin this past week, owner of a very nice Piper Cherokee Six. He dropped his airplane off at SHD for his annual inspection. Hopefully I can give an update in the future about how his inspection turns out.

Trace, and Tobin, it was a pleasure to meet both of you this past week!

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