Ask Paul: Is it a bad engine or bad maintenance?

Question for Paul McBride, General Aviation News’ engines expert: I’m the vice president of a small flying club. We have two Cessna 172s, one with a 160-hp Lycoming O-320-D2J engine and the second with the 180-hp engine, done under STC.

Our maintenance officer very badly wants to upgrade the 160 hp to 180 hp at considerable cost, rather just replace the engine. A big part of his argument for justifying this is that the O-320-D2J is a “known bad engine with lots of reliability issues.”

I have searched in depth and have found nothing to substantiate his claim.

Now we have had a couple issues with the engine. The mag gears broke up, we lost one mag, and the whole gear assembly required replacing. We also had all the cylinder bolts, with the exception of the through bolts, shear off on one cylinder.

Can you please offer an opinion on the O-320-D2J?

Many thanks.

Nigel

Paul’s Answer: Nigel it’s good to hear from you. Even though I am taken aback by some of the information you shared, I’ll do my best to offer my honest opinion.

First of all, I was surprised to learn of your maintenance officer’s opinion regarding the O-320-D2J engine. I truly take exception to that and am curious to know where and how he came to that conclusion?

From my many years of experience with Lycoming, I think you’ll find that the O-320-D2J series of engines has been the most reliable in all operating environments worldwide. I can make the same claim for the O-360 series as well.

I remember very well the problems years ago with the specific Lycoming O-320-H2AD engines, and can assure you that the engineering changes made over time on this series of engines have now resulted in the same reliability as the other 320 series engines.

I, like you, would also like to learn where the maintenance officer acquired his information regarding the reliability of the O-320-D2J.

I must admit that learning that your O-320-D2J engine suffered from broken magneto gears and all cylinder hold-down bolts sheared off on one cylinder comes as a total shock.

Once again, from my experience, when I learn of serious failures like these, I can come to only one conclusion, which I see as a lack of proper maintenance.

I couldn’t tell you when I ever recall hearing of a magneto gear breaking that was properly installed.

With regard to the cylinder base studs, the only time I’ve seen cylinder base hold-down studs shear was when the cylinders were improperly installed and the cylinder base nuts were either undertorqued or overtorqued. Depending where the shear point was located, this can determine which one of these events caused the failure.

As harsh as this may sound, I’d have some serious questions as to the club’s maintenance practices by qualified technicians.

Again, the reliability of both the O-320-D2J and the O-360 180-hp engine are beyond question. They are known to be some of the best performing engines, providing that operation and maintenance are accomplished in accordance with the manufacturer’s recommendations.

Nigel, I apologize for being blunt, but I can only come to my conclusions using the information you provided. I trust that you will understand my response.

Hopefully when a situation like this is encountered, common sense will prevail and more research from industry experts will be sought.

One basic thing that should always be remembered and that is “horsepower costs money,” regardless of whether it’s the initial investment or the hourly operation.

Something else comes to mind that might also be considered in a situation like this, and that is the old question of “wants vs. needs.” You may want more horsepower, but do you need more horsepower? 

From my experience over the years representing Lycoming at venues like EAA AirVenture Oshkosh and SUN ‘n FUN, the most frequent complaint was the cost of our engines and parts. So, if money is the driving decision here, do you really want that higher horsepower if it costs more? 

Nigel responds to Paul’s advice: Your response comes as no surprise, as I have been unable to substantiate our maintenance officer’s claim. The scaremongering worked, however, and we are going to replace, in my opinion, a good engine.