remove the exhaust
I’ve done a few valve freeing, and never had to remove the exhaust. The reinsertion of the valve is usually done working thru the bottom spark plug hole. On the top one I will insert a little LED fixture to see what I’m doing, and the magnet is inserted thru the valve guide. Said magnet has to lock on the tail of the valve stem, the head side of the valve is then lifted with the help of an adequately bent wire.
Tools, needed are an adjustable reamer, the magnet, a piece of wire (coat hanger type), a light small enough to go thru a sparking plug hole, the rope in case the valves don’t close good enough, and a spring compressor tool. If you want to measure the lateral play as in SB388C, then you could buy the dial and fixture, ACS has a kit Wobble test fixture
Regarding the last picture posted, again, no problem from my point of view (sure we’ll find someone with a different opinion here 
), this intake valve looks good. The intake valves don’t get subjected to the intense heat, and don’t rotate, so irregular pattern as seen here is not a problem.
The last pic is an exhaust valve, curiously.
I spent today on this. The #4 exhaust valve was successfully waggled from the rocker cover end, as this video shows
The valve rotates and moves around freely. I had the various tools, rope, and a reamer ready but didn’t need them.
So I think the EGT issue was a bunged-up injector. I had all 6 ultrasonically cleaned and a huge amount of crap came out. This is from the flight along the N coast of Sicily which bunged up my external camera as mentioned here.
I did a test flight and all was ok.
I am also changing back to my previous oil which was 50/50 15W50 and W80, plus Camguard. For last 2 years or so I have been running 100% W80 plus Camguard and I don’t think it is good. 15W50 has some detergent in it and you get a cleaner engine. Also putting in a bottle of Mobil 1 0W30 in the last 5hrs of a service interval (previous threads on this) is a good idea.
The above “assymetric” valve was actually #2 so I did a video of the wrong valve 
but it does rotate as this new photo shows
I think that pattern on it must be old. It would be interesting to compare valves over time…
#1
#3
#4
#5
and 6 is same as 5.
4 is the one which differs.
Back to 15W50.
What not run 100% 15W50?
I am back to 50% 15w50 and 50% w80. That was suggested by the Camguard guy as the best compromise – posted about it here a long time ago. I went to 100% w80 because the temp range was fine for all European flying (I posted about this in detail too). But I think there may be valve issues with 100% w80, although it is ever so hard to put a finger on it… the correlation is not strong.
I actually think moving to unleaded Avgas would be a better option but of course even if it was available it might not be possible for you to use it.
Although I have heard of stories that it’s fine in engines with compression ratios as high as 8.5.
I can use 91UL. CR is 8.5 and non-turbo. However, all these engine issues vary across the range of engines; an O-200 is very different from an IO-540. But practically nobody sells it. Yes I know it is widely available in Sweden
“But practically nobody sells it”
If that refers to 15W50, it’s readily available in the UK. Cheap delivery deal from near you to me in the north.
It was 91UL.
What about Phillips 66 – XC 20W50?
Has anybody been able to source that in the UK? And does anyone have any experience with it?
I’ve seen Phillips 25W60 used in Radial Engines in the UK but I’d guess that’s a bit thick for a 4 banger lycoming.
