My friend Giorgio in Italy had a stuck valve after 450 hours on his factory new O-360. It galled and hit the piston just enough to bend the stem so it wouldn't close. This happened at 12,500' over the Atlas Mountains in Morocco, but he was able to fly on 3 cylinders to Marrakech. There he had a new cylinder & piston installed on #2 and all valve/guide clearances checked according to Lyc. SB 388B. Images of the valve and piston that were removed are
here.
He has always kept all engine parameters in the green and burns 1 Qt. of oil every 25 hours. The only things that are not typical in his operation are
(1) The engine has been operated mostly at lower power settings cross country:about 20" 2200 RPM and
(2) he's stayed with straight mineral oil and never switched to Ashless Dispersant oil.
During his recent engine work he had all cylinders 'decarbonized' and valve guides and stems cleaned, but has observed carbon building up again in the 17 hours flight hours since.
Part III of Lycoming SI 1410, Part III states:
"In engines that have been operating on straight mineral oil for several hundred hours, a change to ashless dispersant oil should be made with a degree of caution as the cleaning action of some ashless dispersant oils will tend to loosen sludge deposits and cause plugged oil passages. When an engine has been operating on straight mineral oil, and is known to be in excessively dirty condition, the switch to ashless dispersant oil should be deferred until after the engine is overhauled."
Can he follow this SI's guidance on cautiously switching to AD oil or is his engine now "excessively dirty"?
Thanks for any insight you can share with Giorgio,
Arlo Reeves
Lycoming SI 1410 Advice
Linear Mode
