Pictorial examples of better maintained /restored 4 door Impalas from 1966 and the Chassis data from the oldride website.
Chassis Data
Model / Wheelbase / Overall Length/ Width / Front / Rear Treads/Tires
Chevrolet / 119 in 213.2 in / 79.6 in / 61.5 in/ 62.4in / 7.35 x 14/8.55X14
More information about the straight six 1966 Impala from the hemmings website:
The buyer of a new 1965 Impala had a choice of 10 engines including the standard
230-cu.in., 140hp straight-six. By 1966 the choice narrowed down to seven engine options. The beauty of the Impala was that Grandma could order an economy car with a straight six-cylinder engine and three-speed manual transmission or Powerglide; and those looking for performance could order one of two big-block V-8s, a 396- or 409-cu.in. engine, even in a four-door Biscayne, the lowest-priced of the full-size Chevrolets, and have it bolted to a four-speed transmission. The VIN tag that is riveted to the driver's side door post will tell you what model the car was originally. For example, if the first five numbers are "16867," you will know that it is a true 1966 Impala SS convertible. There is also a cowl tag below the windshield on the driver's side, which states where the car was built and gives the paint code and trim. Brent Barrett, a technical advisor on 1966 full-sized Chevrolets for the National Impala Association, says some factories, like St. Louis, included a list of options on the cowl tag, while other factories did not.
The cylinder heads themselves are strong iron pieces that rarely ever see head gaskets fail, unless the engine has been severely overheated. The engines were well designed, but given the state of technology at the time, including lubrication qualities and out-of-tune carburettors, many engines need a rebuild after 100,000 miles.
The standard braking system on 1965 and 1966 Impalas was a four-wheel-hydraulic 11-inch drum setup, front and rear. The total swept braking area was 328.3 inches. While certainly not state-of-the-art at the time, the brake system was adequate, and if properly maintained, rarely failed. The standard 14-inch wheels were pressed steel with drop-center rims and were fitted with 8.25 x 14-inch bias-ply tires.
Like all big Chevys of the 1960s, the Impala utilized an independent front suspension that featured unequal-length A-arms with ball joints, direct-acting shocks inside heavy-duty coil springs, and a stabilizer bar. Due to their size and weight, Impalas are known for wearing out lower ball joints, even with regular lubrication. The original ball joints were riveted on at the factory, so if you find a car with bolt-in type, they've been replaced. The upper ball joints, however, last nearly forever.
The rear suspension is stout and has a rigid axle, coil springs, direct-acting shocks and a lateral control bar. The bodies on 1965 and 1966 Impalas were rugged, but as with most 1960s cars, they are prone to rust. Steve Leuing, the National Impala Association and Vintage Chevrolet Club of America's technical advisor for 1965 full-size Chevrolets, says the biggest area of concern is body and frame rust. "Unfortunately, because of the nature of the construction of these cars, they are very prone to rusting in front, above and behind the rear-wheel opening, wheel wells, floors, trunk pan and gutters at the base of the windshield," Steve says. Convertibles are susceptible to severe rust in the front and rear floor pan because water doesn't get channeled out properly. However, one area of these cars, the rocker panels, remains solid unless exposed repeatedly to salt-covered roads. This is due to "flush and dry" rocker panels, which were designed to allow water to flow through, followed by a burst of air to dry out the remaining moisture. The door hinges were built like Fort Knox, but after 40 years, the bushings may need replacing.