Plugs bent over and engine running rough and hot.

[xymox]

Looking at the photo of the valves, the coloration on the exhaust valve is a bit uneven, and it looks like the valve seat may have changed position slightly. If the clearance on the rocker arm adjuster has opened up, that might suggest the valve seat has shifted. It might be time to send the head off to a bug shop for a valve job, including a new guide and seat on the exhaust valve. Might not be anything to worry about, but worth investigating perhaps.

Jeff

Yeah I'm ordering a new valve and seat to be safe. It's actually worn away a bit on the dark side.

[mike.smith]

I disagree in part. The most probable scenario is reusing the same plugs and over torqing and using the same crush washer and the auto lite plugs. Results = too much penetration.

Does anyone know where you can buy crush washers by themselves? I've never found any, so if you remove plugs annually to check them and they are good, then you are forced to re-use the original crush washers.

[mike.smith]

Here's a good, quick guide to what valves should and should not look like:
https://www.aopa.org/-/media/files/aopa ... .pdf?la=en

[sonex1374]

Here's where I get my crush washers, however, they changed their part numbers and the new ones don't have any descriptions so I'm not sure which are the correct ones. You might need to email their support line for an answer.

https://www.sparkplugs.com/SearchResult ... &kw=washer

Jeff

[xymox]

I was actually thinking of just using copper washers as the rest of the universe seems to use those as pretty good Crush washers

[lutorm]

After I ' looked a bit more' I realized that it was in fact making contact with the piston head. See attached picture. So now the question is, why would the clearances move enough to cause interference after over 150 hours?

That looks like our piston did, although a bit worse. (http://sonexbuilders.net/viewtopic.php?f=7&t=4147

In our case it seemed like it could be dependent on how the plug was clocked. When I read about necessary piston/head clearance people seemed to advise to not go below 0.06" or so because thermal expansion and gradual loosening of clearances as the engine wears may allow it to "throw" higher in operation even if you don't have any interference when turning it over manually. The position of the spark plugs did not allow the correct compression ratio while maintaining clearance, so this was my solution (that depression is 0.8mm deep):

[xymox]

In addition I noticed the following,
A crack in between the exaust and intake valves and of course the burned valve. I can only surmise this is why my egts were so hot as the fire was going out most of the time as opposed to only on the power stroke. So junk the head now or what? Yes they are fomoco. I can only imagine how many of these heads have the same issue and goes unnoticed.

[gammaxy]

With valves and seats burned that bad, I'd expect a compression test would have detected it. Did you notice anything when you last checked the compression? I feel the compression by rotating the propeller by hand after every flight.

[xymox]

Only thing telling me something was wrong was missing about 75 rpms and the high egt. Kind of hard for me to tell by rotating the prop if comp feels right

[sonex1374]

So junk the head now or what?

A new head from Sonex is about $300, and a valve job and new valves will be less than half that cost. Might be worth a try to recondition the head and see how that holds up before deciding to replace it.

Jeff