Complete newbie here 

I was looking at buying an airframe that has a O-235 engine that has 1800 hours on the motor..and good compression 

im looking to buy the frame and then put a Viking engine in and sell the O-235

but the engine was new over 12 years ago…

im new to all this… is there any exceptions to the calendar TBO (I’m in Canada)

or does this mean the engine needs to be overhauled even if it’s still under the 2400 hours … because it’s 12 years since new


Michael in Toronto 

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It all depends on what model of the 235 you have. The C and L models qualify for a 2400 hour TBO, but the F, G, and J models do not per Service Instruction No.1009BE. See LINK from Lycoming Service Instruction. 

Canadian law may require an overhaul at 12 years where the FAA in the US does not. More of a guideline than a regulation. Some swear by it, others fly until the engine shows signs of wear and/or lose of power at RPM. 

AOPA has a good article on TBO's. Check local regulations to be sure. A TBO is a guideline that is loosely adhered to, and many time the cylinders and valves only last half that time. We  had an O-235 C1 hit 3.000 hours (on the lower end) and still had decent compression, but it was really tired towards the end. The top end was redone at 1200 and 2100hrs. The C models are very expensive to overhaul. A set of rings alone will set you back $1.600 US. About as expensive as gold is per ounce. My C2C is almost back together. Took me 3 years to save the money. It is the first and last O-235 I will rebuild, but I spared no expense. ALL original Lycoming parts, machining at Divco and Aircraft Specialties in Oklahoma, and I am assembling it myself. Love the process, hate to part with that much money. 

Good luck. 

Appreciate the informative reply.. big thank you 


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