I wanted to update the Mooney community with a new thread on the conversion process I am in the middle of going through on my 78 J switching to a A3B6 motor from a single drive A3B6D. For anyone else considering this, I have reposted the above link from member dhc which has turned out to be an extremely valuable resource for the conversion. My goal is to update the pricing for needed parts and share some of the issues that were a little different from dhc's conversion, even though both of us have converted a 78 J.
The first consideration for anyone is whether a field overhaul, factory overhaul or factory refurbishment is where you want to spend the money. Time for any of these was not a consideration because a field overhaul takes the same amount of time as it does to have Lycoming do its job. All quotes, including factory refurbished were 4-6 weeks, and I stopped flying my J when I started fouling the lower #4 cylinder plug on short final so waiting for an engine while continuing to fly was not an option. 2000 hrs had passed and it was time for a new motor. The cost for a field overhaul from the reputable shops was $27-$29K which included Poplar Grove, Western Skyways and Penn Yan, (varied about $2K depending on factory new or refurbished cylinders). Factory overhauled, (A3B6) from Lycoming was $32K and factory refurbished was $35,500. Interesting to note, a A3B6D is more expensive to refurbish/overhaul than a A3B6 by about $1700. So in looking at cost of ownership over the next 2000 hrs, (10-15 years based on how my plane flys now), the next overhaul would be cheaper on the A3B6 than the B6D. So just in a motor comparison, switching to the A3B6 was about a $3500 upgrade if I look at the cost of the motors and potential future savings at overhaul, $5200 if I take out the next overhaul. So for my plane partner and I, a ZERO time engine logbook, 80% brand new parts engine built to new limit tolerances as opposed to overhaul minimum tolerances, and a significant plane value increase completely made the cost of the factory reman worth the cost.
That all being said, there are some gotcha costs involved, including costs that one would bear during an engine change out/overhaul. You will have to purchase some parts that won't come off the A3B6D such as the prop governor brackets and cable mounts, and the prop governor oil line. Prices varied considerably among the shops out there for these parts and G&N was the best for me by far. The new oil line was $560 from LASAR, $452 from G&N for the same part. $452 is ridiculous from Lycoming when it was $280 in 2014 when dhc did his conversion. The cable brackets were another $50 and $75 a piece, and the prop governor brackets were $147 and $175. Rebuilt prop governor is $1250 from West Coast Governor Service, highly recommend Dan there, btw, (former Navy Hydraulic mechanic so he knows his stuff). So there is roughly $2100 in prop governor parts/conversion for the new motor, about $900 increase to change to the A3B6. Oddly enough, there are two different control actuators that you could get on your prop governor which is differentiated by what side of the actuator the set screw is on. This set screw placement will dictate if you need to use the $147 bracket from Mooney or not, we did not and the part was returned, (literally the only cost savings we had in this entire conversion).
The alternator that comes with the reman from Lycoming will not fit the baffling on the J so you will have to either use your existing or buy a new one. I had just purchased a new alternator 100 hrs ago so I was good there.
New hoses are in order on an engine change and there are some differences because of the oil filter placement on the A3B6 so Ashley from PHT in Tulsa was a great reference there, about $900 for a complete set of hoses.
Other than the prop governor costs, everything is the same between the two motors. Lycoming now uses Slick mags and harnesses so the timing on the motor is at 20 degrees instead of the 26 degrees of the Bendix mag setup. If you wanted to go to the Bendix setup you could, but we are installing a Sure-Fly electronic ignition as soon as they are STC'd so the advance timing of the Sure-fly negates the lost power from the Slick mags and is cheaper and better running than a Bedix mag setup. $1250 for the Sure-Fly.
Total costs: 35500 motor, 450 shipping, 2100 prop gov and acc, 900 hoses, 150 two cases of oil, 600 motor mounts, 1550 new baffles. $41250.00 to date.
Ultimately, the cost of switching to the A3B6 has been worth every penny and because some of the trials detailed by dhc, the conversion has gone relatively smooth. The increase in costs to switch have been minimal because the only real headache is the prop governor, so plan on the extra $1000.