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Wisdom of Using a Mooney Engine
I'm considering adopting a kit with a IO-360-A3B6D, which is an angle valve engine with the dual Bendix mag and counter-weighted crank. What has the brain trust to say about installing this in a -7? My first concern is changing out the accessory case to separate mags so I can install P-mags. How much surgery and expense goes into doing this. Any issues with c-weighted cranks? I vaguely recall some problems, maybe ADs, no so long ago with them, though being a parallel valve guy, didn't pay much attention. Any other issues?
John Siebold |
$$$$$$$$
That is what you will run into trying to convert. Mine was an O360-A1G6D. The gear train, as I remember it, would be excruciatingly expensive to reproduce, plus the need for a new accessory case. What I did was go all electronic. I have spoken with folks who say there is nothing wrong with the dual mags, but I won’t fly behind one. There are conversions that will put a single mag in that big hole, but I have not tried them. Good luck!
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Depends on the Mooney!
Mine came from a Mooney. M20E or F, I forget. It is a IO-360-A1A.
I have a friend who is quite knowledgeable about mags, and has a Cessna 177 Cardinal that has a dual mag. He chuckles at all the objections. All normal 2-mag engines still drive both mag drive gears off of a single crank gear. So there is still a single point of failure. The dual mag just moved that single point outside the accessory case and into a housing. After that, most of the guts are the same, right? |
I0360A1A accessory case
If it helps your decision making I have a I0360A1A accessory case you can purchase for a mere $250. I can't remember if I still have the vacuum drive, but the oil pump is there. I'll check to see if I also have the spin-off filter adapter, prop governor drive, and idler gears.
Personally, I prefer all RVer purchased a new engine for their new airplane. I realize the cost of new is hard to swing for many struggling builders, but sometimes new is cheaper in the long run. |
Appreciate the offer, Danny; I concur, the -7s I've built were "all new". What I'm looking at would be a good deal if it weren't for what are to me the massive unknowns of adapting the Bendix mag, e.g., would it fit the Van's 360 mount. And it's a heavy angle valve. Lycon can build a parallel with the same hp and more.
John Siebold |
The thing about counter weighted cranks is that there are a LOT of different possible counterweight configurations, and they get determined for a specific engine/prop (and airframe?) configuration...so if you just randomly grab a counter weighted engine, and mate it with a random prop, you have no idea if the counterweights are working for or against you.
Such is what we were taught at Lycoming school..... |
John, I have that exact engine in my -6. I "solved" the Dual-Mag issue with dual crank-triggered Lightspeeds, although the later D3000 mag is allegedly quite good (I used mine for the first 100 hours of flight of my -6). One thing that's nice about the dual-mag engine is the rest of the accessories are more logically laid out, like the oil filter, which is about where the RH mag would go. Also there are no intermediate housings for oil filter, governor drive, and vacuum pump pad so a few less chances for oil leaks.
And Paul, this -A3B6D has the same counterweights and bushings as the typically-used-on-RV's -A1B6 does, so no issues there. As to converting to a non-D configuration means you even need to replace the crankshaft. |
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Larry |
I bought an IO 360 A1A and CS prop out of a Mooney, went all electric, EFII. No problem.
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Pendulum absorbers damp a vibratory order. Generally, in pendulum design the roller and bushing diameters set the order. A particular propeller may be happier if some specific order is damped, but if the installed pendulum is tuned to a different order, it's hard to imagine how it could hurt. They are passive devices. Put another way, they damp, not add. If the crank doesn't oscillate at the tuned order, the pendulum does nothing. Parts book says the A3B6D uses the same pendulums, rollers, and bushings as the rest of the IO-360 A and B models with pendulums. The different crank part numbers are due to differences in prop flange drive bushings. If I wanted to run that engine and did not want a dual mag, I'd just install crank triggered ignitions...SDS, EFII, Lightspeed, or EDIS. |
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