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Engine Update

posted Jul 14, 2007

Good News and Bad News

New engine ready for installation

The factory rebuilt IO-360-A3B6 engine is ready for installation

The good news is the factory rebuilt engine arrived on schedule, and in great condition. The other good news is the propeller and governor came back from overhaul with no problems. There’s always a chance that the propeller overhaul shop will find a crack or corrosion in the blades that requires replacing the entire propeller.

Engine mount

The engine mount. The large rings are where the back of the engine connects to the mount. The part of the mount that's facing up in the picture connects to the firewall. You can see the broken U-shaped bracket in the lower right, and the non-broken one in the lower-left.

The bad news is when the mechanics pulled the old engine off, and they inspected the engine mount they found one of the lower U-shaped brackets on the mount was weak and one side of the U actually broke off in the mechanic’s hand as he inspected it. Apparently this is a fairly common thing and getting the engine mount repaired or replaced should only take about a week. It’s disappointing because I was really hoping to be able to fly the Mooney this weekend. However I’m glad they found the broken engine mount now, rather than having it fail sometime in the future. The way the mount is designed, the broken flange wouldn’t have let the engine move at all, but had the mechanics not caught the failure now, we would have had to remove the entire engine at a later time to replace the mount.

Double The Magnetos, Double the Safety

I previously posted about the decision to switch from the single magneto housing design of the Lycoming IO-360-A3B6D to the better design of the -A3B6 which has two truly independent magnetos. Making the engine switch was a little more expensive, since it eliminated the option of overhauling the existing engine.

I was pleased to find out that I wasn’t the only person who decided this was the right thing to do. When I received the July 2007 issue of AOPA Pilot magazine there was an article providing an update on the Cessna Cardinal that AOPA is restoring to give away in their annual sweepstakes for members. AOPA made the same decision that I did to switch out the original engine for the version with two truly independent magnetos.

Julie Boatman writes in the print version of the article (which is slightly different than the online version):

The [1977 Cessna] 177B came out of the Cessna factory with a 180-horsepower Lycoming O-360-A1F6D engine. This engine features the Bendix dual magnetos popular with engine manufacturers in the 1970s as a way to save space in tight engine compartments, and money in the ever-competitive general aviation market. The dual magnetos (sometimes called double magnetos) have independent distributors but share a single rotating magnet and common drive gear to the engine — and occupy the same housing. The Bendix mags, like many other engine accessories, require periodic maintenance, but because they are somewhat unusual, this is regularly missed or performed inadequately. Failure to maintain these mags properly can lead to premature failure and — because they operate from the same drive gear — this can cause engine stoppage.

To eliminate this potential gotcha, I decided to replace the -A1F6D engine with an -A1F6, which includes a standard “two separate mags” setup.

I knew switching to the “two separate mags” setup was the right thing to do, but it was satisfying and timely to read about someone else making the same decision about another 1977 airplane. Plus when I win the AOPA sweepstakes, I’ll have two 1977 airplanes with two truly independent magnetos [grin].

Thumbs Up to Air Power

Since overhauling the existing engine wasn’t an option (due to the desire to switch to the engine design with two independent mags), we bought the Lycoming factory rebuilt engine through Air Power. Air Power delivered the factory rebuilt engine exactly as promised with great communications through the whole process, and they had the best prices I could find. I can heartily recommend Air Power for anyone who needs a factory new, rebuilt or overhauled engine.

Of course, I’ll be even more pleased with the engine purchase when I finally get to fly behind it.

A Few Pictures

I took a few pictures of the old and new engines. Enjoy!

Rear view of new engine

The back of the new -A3B6 engine. The two independent magnetos are the black housings with the spark plug wires coming out of them.

Rear view of old engine

The back of the old -A3B6D engine. The Bendix "dual" magnetos are in the single black housing with a single drive gear.

Mooney with engine removed

Now that just doesn't look right.

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