Borescoping #1

[dkkim73]

Hi Acclaim people, 

My Savvy report flagged cylinder #1 as increased risk of a valve issue. It's not very old, installed new less than 50 hrs ago but who knows. Runs fine (no EGT variance other than the signal Savvy's DNN's apparently detect) and that was only based on a few flights. Have had false alarms before but better safe than sorry...

I've been making a point of borescoping all cylinders when the plane is having engine work done (e.g. oil change, have the mechanics leave things open for 1-2 hrs when I swing by and take detailed pictures).

But looking in this case to just take a quick look at #1 before the next oil change in about 10 hrs. So... does anyone recall offhand if I can scope #1 (Right-side aft-most cylinder IIRC) without pulling the intercooler plumbing? I know some cylinders you can, some you can't, but my memory is a bit fuzzy on which. Just planning how much of an operation it is going to be...

Thanks,
David

@kortopates in case he also knows

 

[M20TN_Driver]

I am pretty sure you can just go thru the bottom plug.  That's what I do when I need to look but don't want to mess with all the upper "stuff".

[kortopates]

Absolutely you can borescope through the bottom plug. You’ll want a stool to sit on doing it this way but this is a popular way to borescope.


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[dkkim73]

Thank you, guys for the quick response. I kind of remember the plumbing getting in the way of *some* of the bottom plugs, just can't recall which positions. I suppose an angle-extension might solve that in some cases. So I was wondering if anyone recalled if this one was a clear shot. 

Interestingly, I did go via the top plugs last time and found it actually harder to get good pics than the bottom which I had used before...

 

 

[exM20K]

I would not spend any MX $ chasing one of these reports.  I believe they have an in-sample vs. out-of-sample problem with this analysis.

I *do* borescope at least every 100 hours.

-dan

[Schllc]

The bottom plug is easier to scope than the top plug, but  removing intercooler on top is only a few screws and two hose clamps. 
Every single oil change I remove all plugs, clean, gap, apply anti seize, and reinstall. 
If it wasn’t so difficult to clean all the oil spilled from removal, I could do it faster. 
This takes me about three hours. 

[dkkim73]

3 hours ago, exM20K said:

I would not spend any MX $ chasing one of these reports.  I believe they have an in-sample vs. out-of-sample problem with this analysis.

I do wonder a bit about ability to control for the "span" of training set. Do you mean that the candidate data is from a larger (unsampled) set of data than is represented in the set used for training? So it looks weird simpler because it hasn't been seen before, rather than that it is representative of the Known-Proven-Bad examples. 

Thanks, guys, for all the tips. I went by after work and looked at it. The valves looked fine, very even signature on the exhaust valve. Good, since it was a new cylinder. 

FWIW to others, no need to pull any plumbing for the bottom plug on cyl #1, straight shot with an extension and spark plug socket. I did use an offset (kind of a funny crows-foot socket I got from another boarder at my last FBO) to torque the wire cap, but you could also probably wiggle in a few wrenches, too...

 

[Fritz1]

since you know how to do it, might as well scope the exhaust valves every 50h, or at every oil change, think that will catch it if anything is going on, some people send factory new cylinders to engine shops like Gann in Georgia or Victor in CA, hone the valve guides and put fancy multi angle grinds on the valves, I have never done it, maybe an overkill, but you could give Gann a call and get their story on the probability of your factory new cylinder burning an exhaust valve and whether it is worthwhile to check the rotocap and the play of the exhaust valve in the valve guide