Lots of good advice here already. Need lots more detail in order to valuate the autopilot, GPS, and the engine status of both planes.
Some off-the-cuff observations:
- If you buy a plane without an AP, but will want or need one (primarily for IFR travel), in a Sundowner you'll be limited to a Century or STEC. I suspect that the least expensive option will likely set you back at least $6,000, and probably more. So if you'll need an AP, get a plane that already has one. Or at least understand the choice you are making.
- Ditto on GPS. If you will want or need a panel-mount, IFR-certified, WAAS-certified GPS, find a plane that has one already. You are probably looking at $10,000 minimum to get a refurbished used one installed; and it could go as high as $15,000. The GPS decision factors include 'enroute only', 'enroute and terminal', 'enroute, terminal, and non-precision approach', and 'enroute, terminal, non-precision and LPV approach approved'. If you want to end up with a truly IFR-capable airplane for travel to almost any airport under low ceilings, the LPV capability has become a must-have. There are already far more GPS WAAS-based LPV near-precision approaches than there are ILS approaches, and the number rises daily. This will be the ILS-like approach that gets you into thousands of small airports that will never have an ILS. Even when the precision approach isn't really needed because of weather, it is by far the safest way to get into unfamiliar airports that have nearby obstructions or terrain.
- You need to assess the instrument panel as a whole, not just the GPS. Still have a KT76 or KT76A transponder? Expect it to require replacement with a completely different model within a year or two (cost: $2,000-$3,000 or more). How about the Comm-nav radios? Old original KX170B's? You'll be fixing or replacing them within a couple of years (cost can vary widely). How about the audio panel? Does it have an integral intercom? If not you'll probably want to upgrade it when you start traveling (music inputs, pilot/crew isolate, etc.). Don't forget the status of the engine instrument cluster and the other flight instruments. All the cluster instruments should work, and give proper indications. The oft-stated claim that 'fuel gauges never work' reflects convenient ignorance. Getting the fuel gauges indicating properly can cost as little as $200 for some bonding jumpers; or it could cost as much as $2,000 for overhauled gauges and tank fuel level senders. The other cluster gauges will run about $200 per unit plus labor, to have them overhauled. There are five gauge units in the cluster.
- The post-TBO engine WILL need an overhaul, and probably sooner rather than later. That cylinder showing 68 is certainly 'legal', but I don't know where it is leaking. It is common for Lycomings to have compressions in the high 70s well past TBO. That one cylinder is leaking somewhere; and I suspect that it is fouling the lower spark plug (or plugs). You can get around that for a while by using fine-wire spark plugs in the bottom positions. If the leak is in the exhaust valve, it will worsen fairly rapidly. With so many hours on the engine, anything that creates a need to work on or change cylinders is probably going to precipitate a major overhaul. If you were buying the plane to keep it for a year while training, then re-sell it, it might be worth the gamble. If you are buying it to use and enjoy for the foreseeable future, you'll get nickel-and-dimed on the engine, and will be worrying about it all the time. When you cave in and do the overhaul, you are probably looking at $20,000 with all the accessories properly overhauled as well.
- The low-time engine may be terrific or may be a complete bust. If it has been flying 75-100 hours per year since the major, AND if the right parts were used (new Lycoming cylinder assemblies, new cam and lifters, etc.), AND if the Lycoming crank is safe from the current ADs, it is probably the safer bet of the two engines. If it was a field overhaul from a small shop, with reused major parts (cylinders, pistons, cam, etc.), and the OH was done fifteen years ago, it will be just as bad off inside as the high-time engine. You have to have the details on the parts used and the repairs performed, and who built the engine during the overhaul, in order to assess the engine status.
- If these planes are priced at $40,000-$45,000, that normally is not nearly wide enough a disparity to reflect one having a run-out engine. Much as I hate to say it, the numbers also sound high for today's market, unless the aircraft with the low-time engine also has outstanding avionics and instruments. Make sure you run some numbers on AOPA's valuator, once you have more detail about the planes, to help you better assess the pricing.
- If you are wise, you will take the pre-buy work-list on BAC, to heart. A valid pre-buy on a plane that is thirty years old needs to be the most thorough Annual Inspection that the plane has ever had. For example, neither of these planes has rear seat ventilation ducts that run under-floor; but BOTH have rear seat heat ducts that DO run under-floor. At a minimum, the status of the under-floor, instrument panel, and front pedestal ducts MUST be verified. If they are original black CAT/CEET ducts, there WILL be corrosion to some degree in some places, on airframe and brake lines. If they are new red-orange SCEET ducts, that's good news; but you still have to have the airframe and brake lines checked for un-repaired or improperly repaired corrosion. We have had planes in at KLUX that contained new ducts, but which had serious corrosion that wasn't fixed. This includes brake lines and retract gear lines that subsequently failed, at corrosion spots that went untreated. The seller should be willing to split the cost of a really serious inspection. He should also be willing to fund (up front or via pricing discount) airworthiness-related repairs (as opposed to cosmetic repairs). Regardless, it is far better to spend (and even lose) $1,000 up front, than to face ten times that much a year later when it's all yours.
- And I have to say that, assuming you follow the advice about a premium pre-buy inspection, it is a mistake to buy the cheapest plane you can find. I don't mean that you should find a way to pay more for an equivalent plane. But if you find a plane that has all the avionics, nav and autopilot equipment, paint, interior, etc. that you will ever want for your your future missions; and the evidence reflects premium maintenance under its current owner; then that plane is absolutely worth paying a premium to get. You might pay $10,000 more for such a plane. But in exchange you will get the equivalent of $50,000 in already-completed and proven upgrades, precluded maintenance needs, etc. Almost any upgrades that you plan to carry out later on will cost you three to six times more than getting them in a newly-purchased plane.
