O-340 Lycoming (Moved Topic from Mx Library)

[sebecker]

What are the service issues and availability of parts for the O-340 Lycoming? Also what are your impression of the engine with a constant speed prop?

[blueldr]

There was a Doyne conversion using the Lyc. O-340 in the C-170. I think it is almost an orphan engine in that it was barely used as OEM equipment and the engines seem to be very scarce. I do not know if the O-340 is still supported by Lycoming. In my opinion, the O-340 was not at all enough more powerful to justify the cost of the conversion.

[Bruce Fenstermacher]

They were used in few aircraft and it is now an orphaned engine not supported my Lycoming. Some parts might be an issue.

[marathonrunner]

Find three and bury them for tiedowns

[sebecker]

Thank you all! I like the tie down response best!

~S

[rsharp]

I have about 70 hours in a 1952 170B with the Doyn O-340 conversion and a Hartzell CS prop. The engine is essentially an stroked O-320 with 8.5:1 compression. The data plate says it is certified on 91/96 octane and makes 170 HP. I have heard there may be as many as five 170's with this setup. It gets off the ground quickly and climbs like a homesick angel! In cruise at 22"/2200 I see about 6.33 to 6.75 gph and 100 knots groundspeed on the GPS. Not much to complain about!
--
Rick

[Bruce Fenstermacher]

Rick it is not that it wouldn't be a fine combination on a 170 until you take other things into consideration.

Buying or owning a plane with a 0-340. The engine is not supported by Lycoming and some parts aren't readily available. As long as nothing wears out or breaks your fine but eventually you will need something. Swapping the engine to another model of Lycoming could prove to be the only way out and that will be expensive today.

Why would one consider installing one today. The STC is not supported so how would one do it. The 180 Lycoming is available and supported, STCs are supported and it won't be any more expensive.

Just like buying a 170 with a Franklin installation. A owner has to know and except the limitations of the engine they have which and the limits are not about performance.

[blueldr]

If you were to acquire a 170 with the O-340 converion, that is probably OK if you realize that you might have a parts problem with the engine. The performance is fine with that engine. In view of the engine factory support, to think of converting to that engine would be ridiculous at this point in time.