The Cessna 120-140 Association Forum

I was googling and saw a thread from the 120/140. Facebook group discussing the O320 from about a year ago. I don’t have facebook so I can’t respond there, but it sounded like several people knew owners with O320s installed. Anyone here have contact with anyone who does? My 290 is getting close to timing out and going back to a C85 or O200 would be a huge tear up since it’s already been heavily modified for the lycoming.

Thanks!

I only found one Cessna 140 with an 0-320 in the FAA registry, in Colorado. You can look it up on the FAA website.

Have you also considered a conversion to the Lycoming 0-235? Reddoch Williams located in NW Florida has a Cessna 140 that also had the 0-290 conversion that was recently removed due to lack of spare parts and replaced with the 0-235. His contact information is in the members list located on the home website of the 120/140 Association.

Being that the 235 is ~10lbs heavier and 10-15 hp less than the 290, I just don’t think I can justify it in my head. Would rather do the work to get back to a C85 striker for the power to weight ratio.

6597 wrote: ↑Fri Aug 28, 2026 12:55 pm I only found one Cessna 140 with an 0-320 in the FAA registry, in Colorado. You can look it up on the FAA website.

Thank you, I found him and tried to call and email. Hoping for a response soon.

I thought one of our members bought the old McKenzie STC. (Gus Warren, maybe?) That would be the place to start looking, I'd think.

I thought one of our members bought the old McKinzey (sp?) STC. (Gus Warren, maybe?) That would be the place to start looking, I'd think.

Gus Warren's STC is for the Lycoming 0-235, 0-290D, 0-290D2 engines. Didn't see the 0-320 on it. Might be a source of info though.

"Back then" (1955) those mods were approved and incorporated into the Aircraft Specification. I'm pretty sure I've seen an Aircraft Specification that mentioned the O-320 installed according to McKenzie paperwork, but could be wrong. The entry for the O-235 is still there today:

*109. Lycoming O-235-C1 engine Use actual weight
Eligible on Model 120 and 140 landplanes with the following limits:
Fuel 80 min. octane aviation gasoline
Engine limits For all operations, 2600 rpm (108 hp)
Propeller Sensenich M76AM-2 with the following limits:
Static rpm at max. permissible throttle setting:
Not over 2340, not under 2240
No additional tolerance permitted
Diameter: Not over 74 in., not under 72.5 in.
Oil capacity 6 quarts (-29.5)
Installation must be accomplished in accordance with McKenzie Aircraft Repair, 1300 North 27th,
Springfield, Oregon Installation Instructions and Drawing L149-0600-244, Sheet 2, dated September 10, 1955;
utilizing components listed in Parts List dated September 10, 1955. CAA Approved Airplane Flight
Manual Supplement dated October 18, 1955 for Cessna 120-140 landplane required when this engine is installed.

Thanks John,

I saw you mention that in a thread a few years ago. I just made a FOIA request with the FAA for rev 34 of A768 to see if it’s on there. I couldn’t find it anywhere else online.