One of numerous innovations from the Pontiac Motor Division in the 1960s was the hood-mounted tachometer, which was conceived by GM designer Ron Hill as a charismatic cure for the overly congested instrument panel of the full-size cars. In The Definitive Firebird and Trans Am Guide 1967-1969 by Rocky Rotella, Hill stated, "While I was in the Pontiac studio, I came up with the idea of placing it outside the vehicle on the hood and designed its shape. The GM patent was issued in my name."
The hood tach was first offered as a dealer-installed accessory in 1967, before its availability expanded to a factory-installed option during the model year. It featured a smooth, rounded housing, and the face had a 180-degree needle sweep, an 8,000-rpm limit, and marks at 200-rpm increments. "Pontiac" lettering and "RPM X 100" were also present, as was a redline that began at 5,100 rpm with V-8s or 6,500 rpm with the OHC-6 engine. According to the GTO Recognition Guide by Paul Zazarine, the GTOs and full-size Pontiacs used a steel-blue background with white characters, but the Firebird employed a black background with green characters. The unit was lit by a single bulb, making it somewhat dim.
A main selling point was that the tach was positioned right in the driver's line of vision, so there would be less eye movement required to read it—and, of course, it just looked cool. Detractors pointed out that the delicate electronic instrument was mounted outside in the elements and would be subjected to additional shocks each time the hood was closed. Another concern was theft, but by using pop rivets for two of the four fasteners (the other two were studs and nuts) the unit was more difficult to steal.
The redesigned 1968 hood tach had a lower profile and slightly shorter housing length than the 1967 model, and it mounted with two studs and nuts and one pop rivet. Its reshaped face also had different fonts, the 200-rpm-increment hashmarks and redline moved to the inside of the numbers, "RPM X 100" was removed from the face, and "RPM" was added to the needle's base cover.
According to the Pontiac GTO Restoration Guide 1964-1972 by Paul Zazarine and Chuck Roberts, a few tach face designs were used in 1968. On the early version, "The characters were [laid out in a] circular shape and the sweep needle was approximately ¼-inch shorter than other 1968 needles. Redline started at 5,100 rpm."
The next design featured the more commonly seen wider-spaced character layout and longer needle, and it retained the 5,100-rpm redline. Another was visually the same but had a higher 5,500-rpm redline for the OHC-6 engines. It was later set up for a V-8 and used with the Ram Air II 400 that arrived in the spring of 1968. A steel-blue face with white characters was retained for 1968, but for 1969 the background changed to black. The 1968-and-newer hood tachs used two bulbs, making them easier to read at night.
Though Pontiac sealed the unit from the elements, fogging issues led to the addition of a hose during the 1970 model year; this line ran from the heater box to the tach to clear its lens. Sometime that same year, the redline color changed to orange.
The hood tach remained available through 1972, but from the dealer only in its last year. Reproductions of the tall 1967 and the shorter 1968-and-up versions are currently available and generally feature upgrades over the originals. Pontiac's unique take on this tachometer's design and placement helped advance its performance image, and it remains a venerated option from the muscle car era.
Article courtesy of Hemmings, written by Thomas A DeMauro.