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Wisdom of Using a Mooney Engine

RV7ator

Well Known Member
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!
 
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.
 
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

I would go with an SDS ignition over Pmags. Then you don't need to worry about the accy case. Better product as well, IMO. You'll want to do some research on the crank and counter weights. You want them to be matched for the hartzel compact hub. I bought a 540-C1B5 and bought different counterweights and rollers to make it a C4B5. In my case, the cranks were the same. In the case of the 540, the 4 denotes a crank set up for the hartzel compact hub. Other numbers may also reference this hub as well.

Larry
 
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I bought an IO 360 A1A and CS prop out of a Mooney, went all electric, EFII. No problem.
 
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.....

Hmmm. Hey boss, did they say exactly that?

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.
 
This is getting interesting

I'm liking the responses. Thanks. As to the counterweights, tracking the suffix back through the Lyc pedigree, half-way back to the basic A1A there's mention of particular weights at particular stations, and the prop plate bushings are keyed differently. So this baby is tuned to a particular Hartzell (part of the deal).

And I'm reading that even with the dual Bendix, this engine fits a the Dyna 1 mount Van's sells for A1As. Da, Comrades?

I know of the crank-triggered EIs, thank you, so I can build my way out of magneto dependent tech.

John Siebold
 
Have the D3000

I bought my engine off of a Mooney, -A3B6D many years ago, did the teardown and assembly ourselves after having all parts certified overhauled. It has been a great engine and experience. Have flown 4+ years on the dual mag without issue, it's reliability is no different than the other mags. The only AD is about not re-using star washers to prevent housing from rotational slipping.

That said, I am looking to upgrade to megajolt Ford EDIS ignition if I can engineer a crank pickup to mount to mag hole.

Wade
 
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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

The conversion from dual magneto to two single magneto is not as simple as changing the accessory housing. The crankcase idler gear shaft locations have to be changed, a different crankshaft gear installed which would include specialized machining of the crank to change the gear bolt size from 1/2" to 5/16" and dowel relocation. It's quite an extensive conversion, we used to do the work at ECi. I don't know what shops can handle it these days.
It would be better to go with a Lightspeed ignition system that is not gear driven. It would be much less expensive.
 
The conversion from dual magneto to two single magneto is not as simple as changing the accessory housing. The crankcase idler gear shaft locations have to be changed, a different crankshaft gear installed which would include specialized machining of the crank to change the gear bolt size from 1/2" to 5/16" and dowel relocation. It's quite an extensive conversion, we used to do the work at ECi. I don't know what shops can handle it these days.
It would be better to go with a Lightspeed ignition system that is not gear driven. It would be much less expensive.

Thanks for adding the helpful details. This reinforces what hgerhardt said, but with more info as to why.
 
I bought my engine off of a Mooney, -A3B6D many years ago, did the teardown and assembly ourselves after having all parts certified overhauled. It has been a great engine and experience. Have flown 4+ years on the dual mag without issue, it's reliability is no different than the other mags. The only AD is about not re-using star washers to prevent housing from rotational slipping.

That said, I am looking to upgrade to megajolt Ford EDIS ignition if I can engineer a crank pickup to mount to mag hole.

Wade

When I added a megasquirt ignition on my 6, I made a custom pickup for the mag hole, using a standard lycoming gear. I made two of them, but only used one with no plans to add the second one. I made it so it could support either magnets or a small 32-1 toothed wheel. I used magnets for the megasquirt installation, but the EDIS will need a VR pickup and 32-1 toothed wheel.

I am afraid to use it on the 540 I am building, due to the reported vibration issues in the accy case. I will be doing a flywheel based pickup.

PM me if interested, as I would like to sell the extra.

Larry
 
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Hmmm. Hey boss, did they say exactly that?

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.

I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.
 
I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.

THis is interesting. I have done some research and found that many have re-clocked their Hartzell on the 540 at a different position from stock (clocking moved lug over) and have seen reduced vibration. Curious to learn your thoughts on that, as the 540 has counter weights as well that are configured for the hartzel compact hub.
 
Hmmm. Hey boss, did they say exactly that?

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.

Right or wrong, that?s what the old guy said....caveat that it is the factory advice filtered by a guy who was teaching his last class after 40 years or something like that....
 
... but the EDIS will need a VR pickup and 32-1 toothed wheel.

36 less one. Just polishing the pins....

I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.

Good discussion of prop clocking here some years ago, with input from Les Dowd. I put an example of blade ringing in post 39.

Propeller mass moment of inertia is usually far greater than the inertia of the crank assembly, so the prop can generally be viewed as an anchor against which the crank oscillates torsionally.

Also a post or two relating to airframe participation (see #33). An A3B6D/McCauley combination may be fine on a Mooney 201, but it's pretty awful on an RV. Been there, done that with an 8A.

http://www.vansairforce.com/community/showthread.php?t=14161
 
Man, the thought of reclocking constant speed prop several times to get it in the best position makes my fingers hurt.
I bought dual SDS ignition with flywheel triggers, can’t comment on how well it works, got distracted rebuilding my brother’s M20C. I installed a surefly on the Mooney, ground checks good but again, the weather here is keeping me grounded. The 100 hour since overhaul Bendix mag quit after first flight after engine overhaul. Using advanced mode.
 
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.........Good discussion of prop clocking here some years ago, with input from Les Dowd. .......... An A3B6D/McCauley combination may be fine on a Mooney 201, but it's pretty awful on an RV. .......

The combination you reference (which is the McCauley paddle blades together with the -A3B6D clocking) might have been awful on your -8, but it's not the clocking necessarily that made it bad, it's the blade style, as you or someone else alluded to later.

The -A3B6D already has the 'preferred' prop clocking that Mike Stewart advocated 12 years ago (in that same thread), which puts the prop aligned to #1 crankpin.

I know from my own -6 with -A3B6D/Hartzell (F7666 blades) that it's quite smooth (of course, that's seat of my pants).
 
I know from my own -6 with -A3B6D/Hartzell (F7666 blades) that it's quite smooth (of course, that's seat of my pants).

I was thinking about the restricted RPM/manifold pressure combination. Yep, it was lovely at normal settings. The problem was flying an approach. The prohibited range shook the airframe, but worse, it seemed to always be exactly the power needed for a glideslope.

Found it...avoid 2250 - 2550 rpm below 15" MAP while descending.
 
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