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Ask Paul: What is this mystery engine?

By Paul McBride · September 5, 2022 ·

Question for Paul McBride, the General Aviation News engines expert: I am considering buying a Thorp T-18 with an engine spec I cannot seem to find in Lycoming’s information.

It is an O-320-E2AC. Serial number L-24270-27AC.

It’s the “C” in both the model and serial number that is throwing me.

The data plate is clear and easy to read, so I am not mistaken. Can you help me understand what this engine is exactly?

Don Gherardini

Answer: The letter “C” tells me that this engine was converted and/or modified in the field.

Here is what Lycoming Service Instruction 1304J has to say on the subject:

“For all commercial engines in which the basic model has been altered or converted to another model designation, the letter ‘C’ added as a suffix on the engine serial number indicates a change from its original manufacture. It will be the sole responsibility of the altering agent to attach the necessary service parts information, along with FAA Form 337, or its equivalent, to the permanent engine records and/or log book, and attest to the FAA as to the airworthiness of the alteration, conversion, or modifications accomplished. In addition, all provisions of FAR 45.13 must be adhered to.”

Now that we know this, it will be your responsibility to do some research on your specific engine. Hopefully, you’ll be able to locate all of the information regarding the changes made to the engine.

My suggestion would be for you to do this before purchasing the aircraft, so that you don’t end up with any surprises.

About Paul McBride

Paul McBride, an expert on engines, retired after almost 40 years with Lycoming.

Send your questions to [email protected].

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Comments

  1. Allan D. Dunlap says

    February 23, 2023 at 12:31 pm

    I have a Cessna 172P with a 0-360- A4M Lyc engine. The engine has an electric oil heater glued to the bottom of the oil pan that heats the oil when it is pluged in. I live in Spokane WA and it can get damned COLD here !! What I would like to know is when it is plugged in for a period of time, is it going to be warm ennuff to keep from forming water inside the engine ?? Or should I plug it in 2 or 3 hours before I start the engine???

    Thank You
    AL

  2. peter havriluk says

    September 6, 2022 at 12:53 pm

    Experimental airplane. No type certificate. I think conformance rules apply only to use as a certified engine in a certified airplane. For experimental applications, I think it it’s the Wild West. The buyer/ buyer’s inspecting mechanic ( either or both need to be conversant with experimental airplanes) needs to have a detailed conversation with the seller. And a good long look at the logbooks.

  3. Jim Macklin ATP/CFII says

    September 6, 2022 at 8:42 am

    If the paperwork on the engines is not correct the whole airplanes might cost $$$$$ to be legal.. An independent AI should check everything.

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