M20J IO-360-A3B6 Conversion Experience

[dhc]

In the early fall of 2014, I suffered a crankcase crack on the Lycoming IO360-A3B6D in my 1979 M20J. I have since replaced it with a factory rebuilt IO360-A3B6. The new engine is about 40 hours into the break-in, and all seems well.

 

Because I utilized information posted on Mooneyspace extensively throughout the process, I am capturing my lessons learned in this series of posts, as a resource to the community. I found that many important aspects of this job were not captured on Mooneyspace (or were perhaps too scattered for me to find), and some information is just simply incorrect (the most egregious being the orientation of the new prop governor cable support arm).

 

I want to give a plug to the guys at Able-Air Inc at KWHP, who offered expert advice while being very flexible with me such that I could perform as much of the R&R myself as my work schedule allowed, then stepping in to make progress when I wasn’t available. Working in this coordinated fashion with Able, I was able to complete the entire process from discovery of the crack to first flight with the new engine in just under 12 weeks, with I’d estimate about 40% owner participation in total hours. (My wife was perhaps less than thrilled how much of those 40% came out of the Thanksgiving and Xmas holidays…)

 

Here are the topics I intend to cover, each in a separate post with its own subject line, such that follow-up discussions on that topic can be more easily grouped. I hope the community will find this overall thread to be a useful container for discussions on the topic of a –A3B6D to –A3B6 engine change for a Mooney 201.

 

01: Initial Investigation: Metal in filter, hoped it was rocker bushing, etc.

02: OH or Factory Rebuilt?

03: Work summary.

04: Hoses

05: Prop governor: the ratio changes, what model?

06: That new prop governor arm--correct orientation, and how to rig,

07: Prop governor: gasket installation

08: The prop oil line that comes with engine doesn't fit!

09: Magneto notes

10: Misc notes

[dhc]

01: Initial Investigation: Metal in filter, hoped it was rocker bushing, etc.

 

The initial sign of trouble that I encountered was copper-colored particles in the oil filter. In all other respects the engine was running great. During the course of investigation, I also found a small oil leak that was eventually traced to a crankcase crack forward of the #2 cylinder base. It remains only a hypothesis for me that the two anomalies are aspects of the same problem, since the crankcase crack pretty much dictates engine removal and teardown, rendering moot the issue of particle identification.

 

My notes and pictures of the crack (enhanced with dye penetrant) are included here.

 

Initial Investigation Notes.pdf

[dhc]

02: OH or Factory Rebuilt?

 

The overall topic of whether to field-O/H, factory O/H, or exchange for a factory rebuilt (“re-man”) is a big one and discussed all over the Internet.  In general, to make a rational decision, you want to mine your files and logs to make a table summarizing the heritage of all the major components and accessories comprising your engine, and from that create some options that you can trade against each other. My table is attached below as an example.

 

In the case of a crankcase crack, the decision is somewhat simplified, because the dominant factor is whether you want to repair your crankcase, or replace it. In my particular case, the existing crankcase was getting old, and had seen more than one repair in the past, so I wanted a newer one. The economics of that decision pretty much drives one away from O/H options.

 

The comparison baseline is $32K for a Lycoming factory-rebuild. These days, because of Lycoming’s switch to roller-tappets within the last decade, conventional wisdom holds that the likelihood of a factory-rebuild coming with a new crankcase and crankshaft is relatively high, because the rate of returned roller-tappet engines to the factory is still low. This issue has been discussed in many places (e.g. Aviation Consumer).

 

A factory new crankcase from Lycoming for an IO360-A3B6D is about $15K. (!) Using one of these in a field O/H would likely drive the invoice past the $32K line even if you assume that the crankshaft and top-end are all re-usable. A local O/H shop developed for me a detailed quote assuming that a lightly used crankcase can be had for ~$7K, and assumed that cylinders and crankshaft would be reused with only light work. This quote ran to approximately $25K: not a very good deal.

For Mooney 201 owners, a subsequent decision is whether to choose the -A3B6 vs. the -A3B6D. This has been debated all over Mooneyspace, so I won’t belabor the point here. The purpose of these posts is to point out the pit-falls of the -A3B6 conversion, once the decision has been made in its favor.

engine-heritage.pdf

[carusoam]

Dan,

Did you mention your background?

Pilot, mechanic, engineer or other technical background...

I'm looking forward to reading your work. Trying to get a feel for who wrote it.

Best regards,

-a-

[dhc]

03: Work summary.

 

I’m attaching here my detailed list of each task performed for the engine R&R. This is an example only, of course, and not all steps may apply to you. Hopefully useful, but YMMV.

 

sanitized_work_summary.pdf

[dhc]

04: Hoses

 

The –A3B6 installation is unfortunately not the same as the –A3B6D in hose lengths. Like many others I took this opportunity to replace my hoses, upgrading all but two to the new Teflon hoses with integral silicone firesleeves. I went with the Stratoflex 124-J series (the “brown” hoses). The catalog that explains the hose size / part number convention can be readily googled.

 

There’s considerable angst here because ideally one orders hoses before the engine arrives, minimizing down time by having everything ready to go when it does. But these are expensive ($100-$200 per) custom parts, so you need to get the lengths right. What’s in the Mooney Parts Catalog is a close but not perfect guide to lengths, given slight installation differences. I am attaching my notes on this matter in the spreadsheet, but think through your own installation carefully.

 

What I also found helpful were Lycoming factory reference photos of the back of both the –A3B6 and -A3B6D engines, as well as the figure labeling the ports. These are attached.

 

 

hose_sheet_sanitized.pdf

[dhc]

05: Prop governor: the ratio changes, what model to use?

 

I got conflicting advice from various sources on these this question: will my old prop governor work?

 

I do not have definitive data to say that my old governor would not. Perhaps someone with direct experience can weigh in. The information that I can directly vouch for is below:

 

* My old governor model: McCauley p/n C290D5-J/T17 (consistent with what Mooney Parts Manual calls out for my s/n M20J)

 

* Mooney Parts Manual calls for McCauley p/n DC290D1/T22, effective for airframe s/n shipped with –A3B6 engines

 

* I received email from the Mooney factory that my old governor would work. I received advice from two well known Mooney shops that I should change my governor.

 

* I got this email directly from Lycoming factory support, confirming that the prop governor ratio is different between the two engines (the ratio is defined as how many governor shaft rotations per engine shaft rotation):

 

The Prop Governor data:

A3B6D – Ratio is .850

A3B6 --- Ratio is .866

Both run CW.

 

Hope this helps.  Let me know if I can be of any more help.

 

Regards,

Frank E. Swinehart

Field Service Technical Representative

Lycoming Engines, a div. of Avco Corporation

Ph. 570-327-7098

fswinehart@lycoming.com

 

* I got direct confirmation from my prop governor overhaul shop (johnsonpropellor.com) that the data sheet for McCauley model # calls for full prop RPM at governor shaft RPM = 2340. This is consistent with the Lycoming-provided data: 2340/2700 = 0.867

 

Based on the above, I decided to install a model #DC290D1-F/T22. It has worked perfectly.

 

I will point out, however, that the prop governor was the source of the biggest headaches overall in the engine conversion. Read on to the next couple of posts about the control arm rigging, gasket installation ambiguity, and oil-line conflict with the engine mount.

 

 

[dhc]

06: That new prop governor arm--correct orientation, and how to rig

 

The –A3B6 installation requires a new prop cable rigging arm, which must be purchased from Mooney. These are the P/N’s:

 

• 660017-003 Prop cable clamp half

• 660017-005 Prop cable clamp half

• 660235-001 prop cable bracket

• 660235-003 governor bell-crank

 

And the governing chapter in the Mooney Parts Manual is 76-00-01.

 

The proper installation of these parts is completely opaque: neither the Parts nor Service manual contain any drawings to provide proper guidance. Worse, on Mooneyspace, there is an often-cited post with an ABSOLUTELY WRONG installation of the both the bracket and the governor bell-crank.

 

I am including both the wrong photos (properly annotated) and correct ones in this post. Note:

1. The proper orientation of the cable bracket relative to the engine
2. The proper layout of the two clamp halves (“thin one on top”)
3. The proper position of the prop cable metal collar in the clamp halves

Proper rigging also requires that full prop speed be attained with cable all the way in (with sufficient “cushion”), and the degree of freedom used here for this model of prop governor (McCauley DC290D1-F/T22) is that the center part of the assembly rotates freely when the 6 allen head screws are loosened. Since the position of the center part is at an arbitrary clock angle when the unit is newly acquired, it is good to scribe the final rigged clock angle for future use, as the photo shows.

 

 

[dhc]

07: Prop governor: gasket installation

 

This was another place where data in the Mooney Illustrated Parts Catalog (which Mooney quoted back to me in response to my questions) conflicted with advice given from well known Mooney shops.

 

In the –A3B6D installation, the McCauley prop governor mates to the engine accessory case with a sandwich of two gaskets and a spacer plate in between. This is the installation depicted in Figure 2, page 76-00-01, of the Parts Catalog (parts -48A, -B, -C). The Catalog and subsequent parts list do not show s/n effectivities on this gasket/spacer sandwich, suggesting that the installation is the same for any s/n M20J airframe (and, by implication, either engine installation). However, the accessory case for the –A3B6 is significantly different in the mounting face presented to the prop governor. See the attached photo “gov_adapter_A3B6.jpg”

 

To cut to the chase, LASAR, Willmar, and the Lycoming factory all advised that only a single gasket (p/n AA-9144, the one with a screen) should be installed. It is p/n AA-9144, the one with a screen. See the attached photo “gasket_A3B6.jpg.” This installation has worked fine for me: no sign of any leaks in over 40 hours.

 

[dhc]

08: The prop oil line that comes with engine doesn't fit!

 

The prop oil line that ships with a –A3B6 from Lycoming is P/N 75167, and it interferes with the engine mount! This is explicitly true on my aircraft (1979 M20J, s/n -0851), and I believe the engine mount is the same for several generations of effectivities for the 201.

 

“Dan” at LASAR came through for me by assuring me that Lycoming P/N 75730 would fit, and in fact it did (see photo). This line has enough “bend back in toward engine core” to clear the mount. However, it wasn’t exactly cheap: $293.72 + tax + shipping.

 

When I called Lycoming to complain, they pointed me to the Lycoming Parts Manual which explicitly shows that P/N 75167 is what constitutes the “standard build” of a –A3B6, so they could do nothing for me in terms of refunding costs I had to bear to purchase the 75730 line. This strikes me as disingenuous, since Lycoming heavily markets the –A3B6 to Mooney 201 owners. Why are they unwilling to simply allow the customer to pick from their menu of existing prop line choices? Nice to be a monopoly…

 

[dhc]

09: Magneto notes

 

Lycoming ships –A3B6’s these days with Slick magnetos. Looking from rear of engine towards prop, the right mag is a Model 4370 (no impulse coupling, 0 lag), and the left mag is a Model 4372 (impulse coupled, 15 degree lag).

 

In switching from the Bendix dual mag, there are a few issues to note:

1. The P-Leads need to be re-wired from the Bendix co-axial connector to the separate hot/ground ring-terminal setup that Slick uses. Look at the attached photo.

 

1. It is important to check if Mooney service bulletin #M20-59A has been performed on your aircraft, and to UNDO it if it has. This SB permits the removal of a shorting strap on the ignition switch whose purpose is to ground the right-mag P-lead when the engine is cranking. This is great for the Bendix dual-mag since both sides can contribute to the starting spark, but in conventional two-mag setup described above, the zero lag right mag must not be allowed to fire until the engine is at substantial RPM, for obvious reasons.

 

The drawings in the SB are almost incomprehensible. I’ve include a couple of hi res pictures. The two terminals shown are the actual P-lead and the Horizon P-1000 tach pickup.

 

1. If you have a JPI engine RPM sensor for the Bendix dual mag, it will not work with the Slick. You need to order the correct sensor. The same connector is used. In addition, in the (non-primary) EDM head units, you need to switch the “cylinders = 8” setting that would have been used for the dual-mag setup back to a conventional “cylinders = 4.” The reason is that JPI uses an inductive loop sensor for the Bendix dual-mag that is physically located at the center of the unit, so it picks up a current pulse from both rotating magnets, hence twice the number of pulses.

 

1. If you have a Horizon P-1000 tach, you need to SEND IT BACK to the factory (“factory”: actually a 2-room office/lab in Orange County, CA) to make an adjustment, or else it will also read an RPM that is 50% too low. This is a primary instrument, hence it’s not user adjustable. Do this well before your engine arrives, so that when the big day comes to start your new engine and fly, you don’t end up being grounded as I was.

 

 

Why the Horizon behaves this way is a bit of a mystery to me, and the woman at the factory was unable to explain, only to confirm that it needs to be done. Unlike the JPI magnetic-induction pickup, the Horizon receives its pulses directly from the P-Leads through shielded wires. My hypothesis is that in the Bendix dual-mag, there is enough cross-talk between two sides that even the spurious pulses picked up on both P-Leads from the other side are of high enough voltage to be counted by the Horizon, but somebody with a scope and more motivation than I do would have to confirm this idea.

[dhc]

10: Misc Notes

 

* Even though the mounting points are exactly the same on both the –A3B6 and –A3B6D, the crankcase is not exactly. It is necessary to do some manual trimming with snips in the areas indicated by the arrows in the attached pictures. BE CAREFUL TO LOCATE AND RETAIN the four baffle nuts (two shown in picture). They fall out easily, and if you lose them or send them back with your core, Lycoming charges $25/pc.

 

* We found it necessary to cut a new hole in the top baffle on the passenger side to naturally accommodate the harness, as shown in attached pictures. The remainder of the harness routing was largely the same as in the original –A3B6D installation.

 

* Lycoming ships these days with the Hartzell ALX-8521LS alternator. I found that it was too large to fit with the existing baffle / airbox. It might be possible to do enough trimming to make things work, but I decided to reuse my Plane-Power AL12-P70 (a great alternator), and send the Hartzell back as part of the core-return.

 

* Finally, note that overall the –A3B6 installation is tighter than the –A3B6D one, and your access will be a bit worse, particularly to the oil filter. In fact, since I have the Aerotech CV1J4 in-line vacuum installed (protects instruments from exploding pump vanes), you can see from the attached photo that it needs to be disconnected at each oil change to make room to remove the filter.

[dhc]

To carusoam:

 

By day I'm an engineer at the Jet Propulsion Laboratory.

 

Regards,

 

Dan

[N201MKTurbo]

Last time I needed a barrel nut, I made a sketch and gave it to our machinist at work. 15 min. Later I had 4 of them that worked perfectly. Cost $0.

Owner produced parts...

[OR75]

Excellent post. Thank you.

[ArtVandelay]

I'm glad the PO of my plane already went thru this.

[testwest]

+1 for Able Air, they were just as helpful and cooperative when 1JX was at Whiteman in the early to mid 90s.

 

  Kinda unsure on that filter Aerotech installation though. You do match the installation diagram on the Aerotech Components site, but exploding pump vanes would exit the open tube fitting on the back of the pump. However, the Aerotech filter does protect the pump against any foreign object entering the system upstream, which is a very good thing.

 

I may have had the FOD thing happen on the twin Mooney and just had to replace a 400 series pump with only 62 hours on it, along with cleaning carbon "chum" out of the rest of the system downstream.

 

And yes, that is an excellent post, quite befitting a JPL employee. We had one of our best Boeing flight test engineers transfer there a few years back, and her "farewell luncheon" included an admonition not to crash the Cassini probe into Jupiter. 

 

Geeks rule.

[wiseng]

I am due for an engine soon.  After reading through all this I am leaning for the field overhaul and keeping the dual mag..

[jetdriven]

The risk of that is not the dual magneto. It's having to rebuild the engine in 300 hours due to spalled lifters, like the guy next to me is doing right now with his piper arrow.

[KSMooniac]

Did he reuse his lifters and cam? What about cylinders? I'm wondering now how much mechanical stress due to sticky valves leads to cam and lifter destruction.

Sent from my VS985 4G using Tapatalk

[romair]

The risk of that is not the dual magneto. It's having to rebuild the engine in 300 hours due to spalled lifters, like the guy next to me is doing right now with his piper arrow.

Byron - I'm confused. Why would doing a normal overhaul result in having spalled lifters? I understand that the new engines have some enhancements, but my engine is 2000 hours and still going strong. I would expect that if I do an overhaul at a reputable shop, I should expect similar longevity as your lycoming overhaul. The two mags are indeed an improved safety factor.

[jetdriven]

Byron - I'm confused. Why would doing a normal overhaul result in having spalled lifters? I understand that the new engines have some enhancements, but my engine is 2000 hours and still going strong. I would expect that if I do an overhaul at a reputable shop, I should expect similar longevity as your lycoming overhaul. The two mags are indeed an improved safety factor.

actually I don't think the separate mags are much better than the bendix dual mag. The trouble is the engines assembled after the mid 90s can't seem to make TBO due to spalled lifters. Metallurgy. Rust from sitting. Take your pick but the newer engines won't last. Ours didn't either. Assembled in 2001 with new cam and re ground lifters from aircraft service specialties. At 1250 hours it spalled 3 lifters and trashed everything.

[aaronk25]

Yep and I had a brand new "lycoming factory new" cam shaft fail in 2.5 years and 400 hours. Lycoming lost my business forever. Reground cams are the way to go at least until lycoming proves their committed to producing or should I say purchasing components that actually last.

Several shops I spoke with perfect regroups cam and lifters due to the component being proven.

[JCD]

On 8/23/2015 at 9:52 PM, jetdriven said:

The risk of that is not the dual magneto. It's having to rebuild the engine in 300 hours due to spalled lifters, like the guy next to me is doing right now with his piper arrow.

I am currently facing an engine overhaul on my '78 M20J 201.  I have had the plane a year and put 100 hours on it and started fouling plugs. Bore scoped the cylinder in question and there was rust.  I bought the plane from an older gentleman that lost his medical.  I guess my pre-buy inspection was not to good.  Took it to a shop to do a top overhaul and when the got it tore down......I got "that" phone call. Lifters and cam are gone.  Now I am faced with full overhaul.

 

I was thinking about going to the A3B6 but the additional airframe mod cost has me scared. I just don't know if it's worth it. 

Do the A3B6D's have a problem chewing up lifters? ( I am guessing an oiling problem?)

 

Is it worth the extra expense to switch to this engine type?

[tony]

That's from infrequent use.  After you overhaul it, just fly the thing......and use cam guard.