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Question about Lycoming bearings

J

jgbmo

Active Member
I've rebuilt a lot of engines over the years, but this is my first airplane engine (IO360-A1A, 200 horse angle valve, small base). I've had the crankcase, crank, etc. all reworked and now I'm ready to assemble. My question is about the holes (or lack thereof) for oil gallery passages in the new Superior main bearing shells. None of them line up perfectly with the passages in the crankcase (but are close), and there are other places where oil passages exist in the crankcase but not the bearing shells. If this was a auto or equipment engine, I'd just drill holes to match so that I could be assured of oil flowing everywhere it's supposed to. I this also the case with the Lycomings? Thank you!
 
jgbmo said:
I've rebuilt a lot of engines over the years, but this is my first airplane engine (IO360-A1A, 200 horse angle valve, small base). I've had the crankcase, crank, etc. all reworked and now I'm ready to assemble. My question is about the holes (or lack thereof) for oil gallery passages in the new Superior main bearing shells. None of them line up perfectly with the passages in the crankcase (but are close), and there are other places where oil passages exist in the crankcase but not the bearing shells. If this was a auto or equipment engine, I'd just drill holes to match so that I could be assured of oil flowing everywhere it's supposed to. I this also the case with the Lycomings? Thank you!
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Mine weren’t really close either, however, there remained a large enough passage to get oil into the cleaance at 70 psi. Don’t need a very large hole to feed that bearing with a 70 psi source. Several areas had a slot machined to allow oil flow around the outside of the bearing shell
 
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I took closer look at where the "extra" holes go. Two are for oil passages to idler shafts at the back of the engine, and the others are for the oil cooling jets that spray oil onto the piston skirts. It seems obvious to me that these bearing shells should have holes for those passages.
 
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