Q: I just bought a Lycoming O-320 engine that was apart for overhaul for a homebuilt project. The engine came with four overhauled cylinders. Three of the cylinders are part number LW-12417 and one is part number LW-12416.
I cannot find any information as to whether the LW-12417 are plain steel or nitride cylinders. I need this information so I can purchase the correct piston rings.
Jerry Rodgers
A: Jerry, the cylinder you have is probably an LW-12416, which is the correct cylinder part number for an O-320 series engine. It is a nitrided cylinder that requires using chrome rings.
My guess is that the LW-21417 number you found is actually a casting number or a sub-assembly number from which the LW-12416 cylinder is made.
The only caution I would offer is if these cylinders were chrome plated while being overhauled in the field, that would require using just plain steel rings.
Normally, if a cylinder has been overhauled and chromed in the field, there will be an engraved number on the cylinder barrel just below the flange.
The AMT Handbook lists the standard color coding of cylinders in appendix 3, usually found on the cylinder base, or on fins between the pushrods;
gray/ unpainted = std steel
orange = chrome plated
blue = nitride
green = steel 0.010 oversize
yellow = steel 0.020 oversize
white = rebarreled cylinder
platinum = cermiNil
2 orange bands = cermiChrome
Additionally, the nitrided cylinders will have cross hatch in the cylinder if it was properly prepaired and will look like spider webbing cracks on a chrome plated cylinder. Do not hone these cylinders.