In my search for a Lycoming O360 the most frequent opportunities obviously are prop strike engines at salvage yards. A usual piece of information given is the crankshaft flange dial measurement. This measurement is of interest, but how much interest? Any prop strike, by Lycoming SB, requires a tear down, which costs about $9K or so. This teardown requirement is regardless of the crankshaft flange dial measurement, which has a max variation of .005”. Even if the measurement is .000" and the prop has hit something (or something has hit it) the SB procedure applies.
So what is there to learn from this measurement about the engine's prospects for having a usable crankshaft? I was recently tempted by a fairly benign RLOC by a student pilot who dug up some sand at low power and the measurement was .000", but, the SMOH was about 1350, so not a lot of hours to amortize the cost. Another prospect is less than 1000 SMOH but the aircraft went through a hangar door while taxiing and then prop hit the concrete when the nosewheel collapsed--not a benign event. The dial on this one is .002". Is this an indication of damage to the crankshaft--and maybe damage to other internal moving parts?
Bottom line to the question, what is to be learned by the crankshaft flange dial out measurement?
So what is there to learn from this measurement about the engine's prospects for having a usable crankshaft? I was recently tempted by a fairly benign RLOC by a student pilot who dug up some sand at low power and the measurement was .000", but, the SMOH was about 1350, so not a lot of hours to amortize the cost. Another prospect is less than 1000 SMOH but the aircraft went through a hangar door while taxiing and then prop hit the concrete when the nosewheel collapsed--not a benign event. The dial on this one is .002". Is this an indication of damage to the crankshaft--and maybe damage to other internal moving parts?
Bottom line to the question, what is to be learned by the crankshaft flange dial out measurement?
