So you want to buy a 310? Can’t blame you, really. They are awesome airplanes; simple to fly, great performance and plenty of room inside. But Cessna made quite a few different models and the prices vary wildly. So which one do you buy? The following is just my opinion, based on owning and working on these great airplanes…
(1) Don’t buy anything with a square tail. There’s nothing wrong with the tail itself, but the 1955-58 models are carbureted with an obsolete Bendix pressure carb. There is only one place that makes the rubber diaphragms and they won’t sell them; they want to keep all the rebuilding work to themselves. The fuel injection system installed in the 1959-on models is much better. The 1959 (last of the square tails) is fuel injected but all of the 55-59 models (square tail) have the cabin floorboards riveted in place. This makes maintenance and cleaning a nightmare. Note: carbureted O-470 engines produce 240hp; the injected IO-470 engines produce 260hp.
(2) Definitely do not buy a 1955 C-310 with the O-470B engines; the main bearings are no longer available.
(3) Starting in 1960 (D-model, first of the swept tails) the floorboards in the cabin are removable. This makes maintenance and cleaning much easier. You also get fuel injection. The 1961-62 are roughly the same as the 1960 model.
(4) The 1963 H-model was the first year with the flexible engine control cables. Before that, all 310’s used Teleflex cables, identified by the rigid aluminum cover. The Teleflex system was good in its day, but now they are all tired, worn out, hard to adjust properly and expensive to repair. Yes, I can change out the Teleflex for new flexible cables, but it’s a lot of work and expense. You will be money ahead to buy a 1963 or later model.
Note: the over-wing exhausts on the D- thru H-models that extend all the way to the trailing edge of the wing have a sort of muffler, right at the rear opening. This “muffler” is packed with several dozen small bags filled with asbestos. By now, most of these planes are so old that the small bags are torn and leaking their asbestos fibers. It’s probably best if you didn’t breathe that stuff.
Also: the over-wing exhaust does not cause wing spar corrosion. The corrosion was caused by improper heat-treating of the 7075 aluminum used to make the rear spar. The aluminum industry finally figured what was happening just a few years before Cessna came out with the underwing exhaust. It’s pure coincidence that the two go together.
(5) The 1964 I- model was the first year with the Y-shaped control column. This allows a center vertical radio stack. Prior to 1964, 310’s had a T-shaped control column that forces you to put the radios in two shallow stacks at the top of the panel. The Y-column is a bolt-in swap for the T-column, but last I checked, the Y-columns were going for over $1000.
This was also the first year of the underwing exhaust system. These planes are a little quieter than the over-wing exhaust. But… the placement of the exhaust pipes pumps a lot of exhaust gases into the wheel wells and flap area. You might want to spend a little time keeping those areas clean to avoid corrosion problems later. This change also added lower engine cowlings that were removable. This feature makes it so much easier to remove the intake and exhaust manifolds, as well as cylinder removal, without pulling the engine. Prior to this, if you needed to do any major engine work, like pulling a cylinder, you had to remove, or at least lift, the engine. These two features, the Y-shaped control column and the removable lower engine cowlings, make this a very desirable 310 to buy. If you can possibly afford it, I would recommend you look for an I-model or later.
Also introduced in the I-model are baggage lockers in the engine nacelles.
(6) The 1965 J-models had only minor changes from the previous I-model.
(7) On the 1966 K-models, Cessna introduced “avionics” access panels on both sides of the nose. With modern avionics, there really aren’t any avionics in the nose, but this removable panels will make servicing the cabin heater and nose landing gear system vastly easier.
(8) The 1967-68 L- and N-models got aluminum landing gear struts and a slightly larger instrument panel.
(9) The 1969 P-models came with either IO-470 engines with 260hp or TSIO-520 engines with 285hp.
(10) The 1970-71 Q-models are similar to the previous N-model but the 1972-74 Q-models got a higher roof, a rear window and a larger, higher windshield. Available with either IO-470 260hp or TSIO-520 285hp engines.
(11) The 1974-80 R-models are the last of the line. Easily recognizable by the much longer nose with a large baggage compartment. These came with either IO-520 or TSIO-520 engines, all with 285hp.
Note: Turbocharged 310’s: lots of fun, lots of power at higher altitudes, but a huge maintenance hog. You will spend a lot of money maintaining a Turbo 310.
Oh, just a word about the Cessna 320… this is nothing more than a turbocharged 310. Sometimes you will read that the 320 is longer than a 310 but that’s not true. The aft cabin bulkhead was pushed back about 18 inches so the interior is longer than in a 310. But the outside dimensions are the same.
Personally, I love 310’s, but then I’m biased. Yes, they burn a lot of gas, but they do not burn twice as much as, say, a C-182 with the same engine. People forget that yes, you are burning twice as much gas per hour, but you are also going about 50% faster. So you are not burning twice as much per mile; it’s more like (roughly) 150% as much as a C-182 (per mile.) Pick out the best model you can afford and go have fun.