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Looking for Advice on Borescope Pictures

AaronG

Well Known Member
I have an RV-8A (2004) with factory new Lycoming O-360-A1A and 575 hours. Typically when I see borescope pictures on the site, the valves look clean and it is easy to see heat damage. I have attached a few pictures of my recent borescope and I’m not sure what to make of them. Looks like lots of lead deposits. All 4 cylinders look about the same. I’ve started adding TCP to the fuel, but doubt it will undo the buildup. For the engine experts on the site, any recommendations going forward? Just continue to fly, and continue with borescope and compression each year? Remove cylinders and clean off deposits? Other?

Compressions are all good, and the engine runs great. I have always aggressively leaned on the ground, in climb, and run at peak EGT in cruise (any leaner and the engine runs rough). I have run the engine a lot at low power (40%-50%) in cruise, and in the winter the cylinder heats are in the 275F-325F range. Not sure if one or both of these are causing the buildup. Any thoughts on root cause would also be appreciated.

Aaron
 

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I have an RV-8A (2004) with factory new Lycoming O-360-A1A and 575 hours. Typically when I see borescope pictures on the site, the valves look clean and it is easy to see heat damage. I have attached a few pictures of my recent borescope and I’m not sure what to make of them. Looks like lots of lead deposits. All 4 cylinders look about the same. I’ve started adding TCP to the fuel, but doubt it will undo the buildup. For the engine experts on the site, any recommendations going forward? Just continue to fly, and continue with borescope and compression each year? Remove cylinders and clean off deposits? Other?

Compressions are all good, and the engine runs great. I have always aggressively leaned on the ground, in climb, and run at peak EGT in cruise (any leaner and the engine runs rough). I have run the engine a lot at low power (40%-50%) in cruise, and in the winter the cylinder heats are in the 275F-325F range. Not sure if one or both of these are causing the buildup. Any thoughts on root cause would also be appreciated.

Aaron
The valves look good to me.

If you can run mogas or UL it will of course slow or stop the lead buildup, but I have not ever heard of anything you can do to clean it. I hope someone has some ideas.

Advice from people like Mike Busch with cases like this is usually "keep flying".
 
MW 50

If you install your own methanol water injection and run enough hours at 75% to full power with the water/methanol on, it will look virtually new and just assembled.

Do a you tube search for MW50 on the BF109. The germans run 50/50 Methanol Water mix in a very simple & reliable setup for emergency power get aways when they only had low octane gas available in WWII.

The high power reno racers run it to allow very high Manifold Pressures.

I used it to clean up a 540 with 10:1 pistons that had been run lots of cross country flights with reduced power and cooler CHT'S It only took 3 or 4 flights to do most of the work.

The video seen here:https://youtu.be/1PA70pN6zPM

shows US govt NACA tests on the Allison V12. You can figure out how much water you can spray into the intake in flight by the Allison tests.

The reason for water /methanol is to allow either advance ignition timing and/or the use of lower octane fuel without detonation. Either one allows more HP

The cleaning of deposits is only a side effect.

Most of the Reno guys build their own systems.

YMMV

Have fun. At the very least the first 10 minutes of the video is an eye opener and worth watching.
 
From a Mike Busch webinar - A cylinder head temp minimum of 350°F is needed for lead removal. He said that the optimum CHT for Lycomings is 400°F, 380 for Continentals.
It sounds to me that low power putting around is hard on engines.
 
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