What engines should I avoid?

QUESTION: I have a 1969 Skyhawk with a Lycoming O-320-E2D engine. I think it is an excellent engine. I would like to update to a 1975-1980 Skyhawk. I heard Lycoming had trouble with engines in 1977-78. Is that true? What engines should I stay away from? What year did the company come out with the 160 hp engine? What’s the TBO on those engines?

James Kobus
via email

ANSWER: The 1969 Cessna Skyhawk was a good engine/airframe marriage, but like everything else, consumers wanted more power. Cessna and Lycoming were looking at massive production volumes in those days and chose to bring out an engine that could be manufactured in large numbers on a new computer- controlled machining center. The 160 hp O-320-H2AD was introduced in 1976 and was in production until 1980.

The concept was great, but suffered some challenges. The result was an engine that experienced problems in the valve train area, which manifested itself with cam and tappet spalling (metal fatigue resulting in fragments flaking off the metal surface).

With the problems came solutions. Around April 1978, a change was incorporated that modified not only the camshaft, but also the tappet body. This change also required a new crankcase to accommodate the new components.

To keep everything traceable, Lycoming maintained the engine model, but modified the engine serial number by adding the letter “”A”” to the suffix. As an example, the original configuration would have had a serial number such as L-XXXX-76 for the O-320-H2AD series engine. The engine incorporating the changes had a serial number such as L-XXXX-76A. This allowed Lycoming to modify the original configuration engine if it was ever returned to the factory and still know it had the latest modifications. This still holds true today.

If you are lucky enough to find a mid-1970s Skyhawk that you’re interested in buying, just check the engine serial number on the data plate and do a close review of the engine logbook. If the engine has the latest configuration, it will have a serial number ending in 76A.

Should you find an aircraft that still has the original configuration of engine (they are out there) the selling price may be more attractive. Before making any decision to purchase this aircraft, I’d suggest you contact a Lycoming distributor to see if it offers an exchange for a factory overhaul or rebuilt engine that brings it up to the latest and greatest with no additional charge for turning in a plain old -76 engine. Remember, to get all of the “”good stuff,”” the crankcase, cam, and tappets must be changed.

The TBO time has always been the same regardless of the configuration and remains at 2,000 hours.

I’m sure you’ll hear lots of “”scuttlebutt”” in the field regarding the O-320-H2AD engine, but with the -76A changes, I’d put it in the same class as any other Lycoming 320 series. Remember, there are certain things you as the operator must do to allow an engine to reach its potential and make it to TBO. If you operate and maintain it in accordance with the manufacturer’s recommendations, this series engine is more than capable of reaching TBO.

Just as an aside, there have been many Skyhawks with the H2AD engine that have been converted to the O-360 series 180 hp Lycoming engine under a couple of STCs. This just proves again that people buy horsepower.

Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.


  1. says


    I am about ready to purchase a 172 with a Lycoming 0-320-E2D. It was factory overhauled in 2011. The serial number is L-30951-27A. Is this a 160 horse engine? It was rebuilt by Mattituck Services, INC. Anything that I should look specifically for with ADs?

  2. Al says

    Dear Sir
    Having a cold and hot starting problem with a Lycoming in a Archer.
    Carb rebuilt, new Slick mags, cleaned priming system, new plugs
    Don’ know what to do?

  3. Irvyn Nieves says

    Sir: I will like to know your opinion. I want to make a conversion of my 1975 C-172 M to 180hp. What will be more cost efective, an stc for my O 320 E2D or buying an O 360 engine (new or OH). Which will have a better performance? Irvyn Nieves

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