PT20J

I recently swapped out an IO-360 A3B6D for a factory rebuilt IO-360-A3B6 on a 1994 M20J. I've accumulated about 12 hours on the new engine. I've been running at 25"/2500 rpm, 50-deg ROP at low altitudes to break in the cylinders. The airplane has a JPI EDM 700 with new CHT probes. The factory probe is on cylinder #3 with an EDM ring probe under it (no spark plug gasket probe), and there is good agreement between the factory gauge and the EDM on #3. The baffles are all in good condition with new tight-fitting GeeBee seals. All 9 EDM probes (4 CHT + 4 EGT + oil temp) read within a degree of each other before engine start. I consistently get the following CHTs (+/- 5 deg): 1-360, 2-380, 3-360, 4-375. EGTs are: 1-1390, 2-1410, 3-1400, 4-1420. This isn't a big spread, but I'm curious if others see similar. It's interesting that the even (left) cylinders are hottest. On the other hand, that side has the engine air intake, the cabin air intake, and the oil cooler, all of which I would think would take cooling air away from the cylinders.

No, actually it all went pretty smoothly. I did a lot of research beforehand and had all the parts ready to go. I owe a lot to those on the forum that went before me as their insights were very helpful. For instance, we would not have thought to reinstall the right magneto grounding link on the ignition switch if it hadn't been mentioned here. My IA owns a M20C and has done engine changes, but never on a M20J. We worked on it together and his experience and my research made a good combination with no real surprises. Even with both of us working on it, it took ten full days to hang the new engine.

I just completed installing an IO-360-A3B6 replacing the A3B6D on my '94 M20J. I have nothing against the dual mag engine and flew happily and uneventfully behind one in a '78 M20J for many years. But I bought the '94 with a run out engine and after talking to Lycoming and top-rated magneto shops, I decided to get a factory rebuilt A3B6. The factory rebuilt part of the decision was mainly to get the roller tappets. The move away from the dual mag was because it turns out there are a lot of differences between an A3B6 and an A3B6D -- even the crankshaft is different. The dual mag IO-360 never really took off and over time, parts are likely going to get more expensive than for the more common single mag version. Lycoming backs this up with money - I got a discount for turning in a A3B6D core for an A3B6. The conversion is relatively simple and really well addressed at the beginning of this thread, so I will only address a few areas of confusion. The biggest area of confusion is the prop governor. You need a McCauley DC290D1/T22. I did an exchange with Dan at West Coast Governor Service. Dan is very knowledgeable and helpful and I highly recommend him. Procure the Mooney brackets listed elsewhere in this thread and also listed in the Mooney Illustrated Parts Catalog (IPC). Mount the governor and brackets before installing the engine -- there is minimal space between the governor and the firewall. To mount the cable bracket, you have to remove three screws from the back of the governor, add the bracket and replace the screws. Do not remove all the screws or the governor will come apart. The governor control arm can have the clamp screw in one of two orientations and this seems to cause confusion. The Mooney bellcrank is symmetrical and can fit either governor arm. Just flip it around to clear the screw. The bellcrank tab goes against the governor control arm side that has the protruding screw head. This sounds confusing, but it is pretty obvious when you have the parts in your hand. You'll need a longer AN3 bolt and spacer to attach the prop cable rod end to the bellcrank. You can make these up with shop parts or get the parts listed in the IPC. Once mounted and connected you will probably have to reclock the control arm to get the proper prop control movement. The prop control needs to be able to reach the high speed stop on the governor with some cushion before hitting the instrument panel per the Mooney Service Manual. To properly adjust the control arm DO NOT loosen the clamp screw and rotate the arm. This will mess up the internal governor settings. Instead, loosen the 6 screws on the back of the governor and rotate the whole control arm assembly as required and then tighten the screws. The next area of confusion concerns the prop governor oil line. The line supplied with the A3B6 will interfere with the lower right engine mount. There are three solutions. Lycoming has a different line for Mooneys. It is listed in the Lycoming parts catalog for the engine. No MSC I talked to has ever used it. The Lycoming field rep I discussed it with doesn't recall anyone ever ordering it. It costs several hundred dollars and Lycoming doesn't stock it, so it takes a few weeks to get. This is not your best option. The second option is that Lycoming SI 1435 permits the use of a flexible hose in place of the rigid line. The third and best solution -- used by every MSC mechanic I discussed it with -- is to just bend the line slightly to avoid the interference. My mechanic did this with some difficulty -- it's a stainless steel line and not easy to bend without damaging it -- but with some gentle coaxing he got it to fit acceptably. The hoses were pretty straightforward -- all the proper lengths are listed in the Mooney IPC. What isn't obvious is that the oil cooler needs to be rotated 180 degrees to that the fittings are on the outside away from the engine. (Thanks to Don Maxwell for pointing that out). The restrictor fitting for the oil pressure transducer on the A3B6D is a right angle and this needs to be changed to a straight one (610013-511) for clearance purposes on the A3B6. If you are reusing your baffles, get new seals from Guy Ginby @ GeeBee (800-556-3160). They're the best.

There are two pertinent Mooney Service Bulletins: M20-264 (AD98-24-11) to replace aileron control links with gusseted parts. This was done on my airplane in 1998 by installing the Mooney factory kit. M20-289A to change spacers in the links to prevent interference with the landing gear bellcrank. This was done on my airplane in 2005. Since I recently purchased the airplane, I have no way of knowing how long this rubbing has been going on. It occurs at wing station 133.0, and looking more carefully at the IPC, I see that the tube is actually called AILERON CONTROL TUBE ASSY at that point rather than a CONTROL LINK (the control tube bolts to, and is an outboard extension of, the control link). I've attached a picture of the rub point with most of the grease wiped off. Next thing to check is that the spacers are correctly installed per M20-289A. The Service Manual calls for using MIL-G-23827 grease on the guide blocks. Traditionally this was Aeroshell Grease 7. This grease spec. has been superseded by MIL-PRF-23827C which specifies Type I (metallic soap thickener) and Type II (clay thickener) greases. The two types are not compatible. Aeroshell 7 is Type II. I found evidence of at least three different greases having been used on my guide blocks. I cleaned it all off with Stoddard solvent and regreased with Aeroshell 7. It only requires a thin coat. There really isn't any way to hold a lot of grease around the thin phenolic blocks, and forcing a lot of grease in there just makes a mess that collects dirt. Skip

During annual inspection, I noticed a rubbing noise emanating from within the left wing during the last inch or so of the left aileron travel in the up direction. Some investigation revealed that the sound comes from the aileron control link rubbing on the aft side of the phenolic guide block at wing station 133.0. The paint on the tube is rubbed off, but the tube appears undamaged and there is no metal-to-metal contact. I cleaned all the wing guide blocks and regreased with Aeroshell 7 to no effect. The right aileron does the same thing to a lesser extend, but I haven't opened up the right wing yet to verify that it's the same guide block. I'm wondering if anyone else has experienced this and found a way to correct it.

I removed the trim wheel and gearbox assembly from the airplane to examine it. The steel trim wheel shaft runs through a hardened brass bushing. In my case, both parts were worn causing the wobble. The service manual doesn't mention lubricating this part -- probably because there really isn't a good way to lubricate the bushing without removing the chain, driving the roll pin out of the sprocket and removing the trim wheel/shaft and applying grease. A better design would have been to use a standard size oilite (oil impregnated sintered bronze) bushing. I ordered a new shaft and bushing and plan to drill a small hole in the top of the bushing. That way, at annual I can remove the plastic chain cover and pump some grease in with a grease needle. Skip

I've noticed a bit of wobble in the trim wheel on my M20J. It wobbles maybe a quarter inch left to right when the wheel is grasped at the top or front. Anyone know how much wobble in the bushing is normal?