The International Cessna^® 170 Association

I’ve owned my 170B for 28 hrs with no issues. This spring I had low compression in one cyl. Tried lapping the exhaust valve twice so cylinder removed. Exhaust valve distorted and worse the valve tapped guide is broken. Engine has 1500 hrs, 1000 since overhauled. I’ve been quoted 37K for an overhaul. Engine is a C-145-2. Is it worth considering upgrading to an O-300 and what would the cost be?
Doug Eshelman
‘52 170B 8074A

The C145 and O300 is essentially the same engine…so it’s not an “upgrade”.

If all you have is a cylinder problem….I’d recommend you simply replace the cylinder, and continue time-in-service.

Also be aware that the O-300A and O-300B require an eight-bolt while the O-300C and O-300D use a six-bolt prop.

Unfortunately the case has to be split and time on engine will prob be an overhaul. Engine has to be shipped to a shop.

Kind of stuck in a hard spot since you have to split the case for a broke hydraulic boy I take it. The internal work required difference for an IRAN vs Overhaul is not much more. Because for the IRAN you'd likley measure the crank and inspect the cam anyway and likely replace the main and connecting rod bearings at a minimum. Might as well send the crank for inspection as well as the cam, gears, rest of the hydraulics and bodies. But then you get into the other 5 cylinders, inspecting and repair. And then the carb and magnetos and don't forget buying the new thru rods.

Personally, I'd be ready for an overhaul, though I'd be doing it myself, (my third on a C-145) so my labor is free, but I'd make the decision after I disassemble the engine and did a more complete inspection. Sending it to a shop, you don't have that option most likely.