Ask Paul: Narrow deck cylinders, the Twin Comanche and a Lycoming milestone

Geez, it’s really beginning to look like I’m losing it when it comes to misstating things in my columns. The most recent concerned the “Wide Deck” vs “Narrow Deck” cylinder column in my last column.

I thought I’d explained the difference between the two and used an example of the Piper Twin Comanche PA-30 as being the first to use nothing but the Wide Deck configuration. Boy was I wrong, and thanks to my “old” friend Charlie Melot, who happens to own PA-30 serial number 410 so he would know, I was informed of the error of my ways and, with his enlightenment, returned to the straight and narrow path.

Thank you Charlie! Other than the mention of the PA-30 never being produced with Narrow Deck cylinders, the rest of the information was correct, to my knowledge.

So there isn’t any confusion, the Piper Twin Comanche was built with engines using the Narrow Deck cylinders and, as Lycoming did a rolling production into the Wide Deck cylinders, they were eventually used on the PA-30.

Let me try to explain how I came to throw out the 1963 date about the cylinders. For you old-timers like Charlie and me, the the Twin Comanche sets an important milestone as far as Lycoming history is concerned and the impact this important change had on Lycoming engine TBO times.

[Read more…]

Ask Paul: Wide deck vs. narrow deck engines

I recently received a question from a friend of a friend in Texas regarding the difference between a “Narrow Deck” and a “Wide Deck” Lycoming engine. This has been confusing to many, so let’s see if I can shed some light on the subject.

The difference between a Narrow Deck (ND) and a Wide Deck (WD) configured engine is easily determined by checking the specific engine serial number. The WD serial numbers end with the suffix “A,” such as L-0000-36A on an O-360 series WD compared to L-0000-36 on a ND.

There are a few exceptions to this, such as the O-320-H series and O-360-E series, neither of which have the suffix “A” but still contain WD cylinders. [Read more…]

Which cylinder is where?

Q: Over the last three years of annuals I have had three different mechanics. The mechanic does the compression check, calls out the cylinder number and I record the values. It appears to me that the mechanics might be confusing the cylinder numbers and I can’t find anything online that tells me in what sequence they are numbered.

My questions: What is the sequential numbers of the cylinders on my Lycoming O320E2D? What may be the primary cause of compression loss? What repair is required to correct the problem?

STEVE SARCHETT, via e-mail

A: This is one of those questions that more people would like to ask, but are hesitant to do so because they may get a few chuckles from their friends for asking such a basic question. Steve, I’m proud of you for bringing up the subject and I can guarantee that many pilots out there are also confused as to which cylinder is located where on their engines.

[Read more…]

Tips to reduce spark plug fouling

Q: In my pilot club meeting last month, a pilot complained of spark plug fouling before takeoff in our Grumman Cheetah with 150-hp Lycoming. I suggested that after starting the engine, and before taxiing, she lean the mixture, keep it lean while taxiing and put on full rich for run-up. However, if there is a delay — say she’s fourth in a line of four airplanes for takeoff — she should lean until cleared for takeoff.

Another member cautioned that leaning while taxiing can burn up a cylinder. I say that while taxiing the engine rpm is too low for a lean mixture to burn a cylinder. My brother says not leaning may, in addition to fouling plugs, cause a valve to burn or other damage.

What say you?


[Read more…]

A ploy to sell more engines?

Q: While TBO is recommended as 2,000 hours or 12 years, whichever comes first, the brokers trying to sell me a used plane always belittle that second limitation, chalking it up to Lycoming wanting to sell more rebuilds. Can you clear the air on this one?


A: The text of Lycoming Service Instruction 1009AT, which addresses “Recommended Time Between Overhaul Periods,” has always been a controversial issue. While it lists the recommended hours for each engine, it also includes a rather profound caveat that has become a point of discussion by many: “All engines that do not accumulate the hourly period of time between overhauls specified in this publication are recommended to be overhauled in the 12th year.”

While it was generally thought to be a ploy by the engine manufacturers to sell more parts or factory overhauled or rebuilt engines, this was not the case.

Both Lycoming and Continental offer factory exchange engines as an alternative to a field overhauled engine at competitive prices. This has generated many engines being sold on an exchange basis, while providing both manufacturers with a realistic learning curve about their engines that have been in service under various conditions and times over a period of years.

[Read more…]

What to do about a ‘slightly’ rough running engine

I always look forward to hearing what you have to say, so here is my question: I fly a 1954 Piper PA-22/20 with an O-320 (no suffix) Lycoming, with about 975 hours since major. I fly it 150 to 175 hours per year, and keep up with all the maintenance an old ship requires. The engine runs beautifully, takes about 1/2 quart of oil between changes, has no leaks and has good compression. However, when I pull back the power for a long descent (2,300 to 2,100 rpm), I get a “”slightly”” rough running engine. If I reduce further, to 1,500 or so, it smooths out. I had the prop statically balanced at a reputable shop and it seemed to help a little, but I was wondering if dynamic balancing would be the next place to look, or is there another direction?

[Read more…]