Why not have the engine overhauled or perform IRAN by the reputable shop (what are they quoting for repair?) or overhaul yourself with the help of a competent/experienced A&P. What engine do you have? Is it an older narrow deck, non counter weighted version?
I'm actually not sure what "narrow deck" refers to. It's an angle valve engine, IO-360 A2B
The overhaul quote from them is ~45k and is likely to go up 10k if the crank is bad, and another 4-5k if the case is bad. That's a new engine price, but without a new engine wait. It's really shitty because either I'm looking at 75-100% of the cost of new and a 6mo turnaround or 100% the cost of new and 18 months of downtime. There are no good choices there.
How did the builder incorrectly assemble the case, a problem sealing or torquing?
The thread was misrouted in several places, resulting in fairly pronounced leakage. There was silicone in a couple places it should not be (creating space between case halves and supposedly fretting). There were several nuts that are supposedly directional and were installed upside down. For an engine to leak oil as badly as it did, after overhaul ~2.5 years prior to first flight, and only being flown for 4 years, suggests some sloppy assembly to me.
Cam and lifters are “almost” a throw away on overhaul. Sadly not surprising. If an older engine, is the cam gear integral to the camshaft, if not you will need accessory case mods to install a new style cam. Get the new Lycoming DLC coated lifters and you will likely never have a cam problem again. The main bearing was installed correctly on final case assembly or the crank would have never turned, after they peened it by incorrectly assembling the case halves the first time (Should have realized and replaced the bearing, but the bearing wear is not where the peen marks are?).
Plan was new cam, and DLC lifters. You obviously know more about the main bearing than I do, and I can see why you would say that, but by messing up the bearing alignment, even if it was noticed and corrected, it was negligent for the builder to just re-assemble without checking it.
Case fretting is not uncommon, does the case have dowels on all the thru studs? Likely not, and if not, have all mods installed at case overhaul. Were the cylinders new at overhaul or unknown used. If new should need little work, you had no compression problems. The piston pin plug wear is strange. Usually the tip is worn down not the sides like yours. What happened there, looks like latest piston plug style?
Not sure about doweling. At least one stud appears to have doweling. I don't know what happened with the pin plugs, but I believe the engine shop is implying that the tolerances may have been wrong - potentially installed loose.
If replacing with new and you want more reliability get away from the 200 HP angle valve and install an injected parallel valve engine. Maybe it is more readily available and less expensive. The angle valve engines just seem to have more problems and are on the edge of design reliability. The lower the horse power the fewer the problems, especially as far as case fretting and cylinder work is concerned.
Unfortunately, the parallel valve engines are more readily available and less expensive, but anyone selling a newly overhauled one would need a core and I'm sure that would bring the price up. I have a core that happens to be angle valve, though I can't confirm which parts are good or not. My attitude towards the engine is that I would like either the same power or more power because I live and fly in Colorado and can use every last bit of climb and cruise performance at these density altitudes. Effectively the minimum XC altitude here is 7500 feet and 10k is extremely common. When crossing the mountains I'd fly at 12-14k plus and I need all the power I can get.
I was dead set on 10:1 compression pistons with this engine before the shop told me they cause poor oil consumption. If changing in any direction I would want an IO-390. I guess reliability is fairly persuasive and I'm happy to listen to arguments for it, however.
I am an A&P / IA and auto shop owner, am very comfortable working on engines (not volunteering), have done a fair amount of major internal engine work (auto and aircraft), have been supervised and taught by a local aircraft engine builder with a fantastic reputation before doing aircraft engine work on my own (built several engines with him), and feel this engine may be economically, reliably (for an angle valve) , and safely rebuildable.
I do understand that many would rather have new for peace of mind. Let’s see if I regret this post.
GM
I'm pretty close to a layperson so I just have to go on what experienced people like yourself and the engine shop have given me. The shop that disassembled my engine has a local reputation for good work and they are the best local resource for handling an overhaul, as far as I can tell. They were kind enough to walk me through the problems in person before quoting me for the overhaul, and the $45k price (+crank? +case?) is more likely attributable to the present level of demand and complete lack of parts supply. I'm under the impression that given the history of the engine this shop would not put their name on something without dotting every i and crossing every t on the overhaul as though it were a certified airplane. I haven't asked about reusing cylinders. My risk tolerance dictates it should probably be overhauled and not IRAN, but it's worth noting that the metal debris caused damage throughout the engine.
I appreciate your input, but I don't see a way out. This is minimum 45k for an overhaul, possibly ballooning to 60k. All the alternatives look like used engines or overhauls of similar cost with less certainty about the track record of the work. Or an 18mo wait from Lycoming.