1966 Mercury Comet Cyclone GT

Muscle fans can be forgiven for overlooking the 1966 Mercury Comet Cyclone GT and other Mercury muscle cars in the mid-1960s. Rarely did it feature anything that couldn’t be had for less money over at Ford, and sometimes the hottest Ford pieces weren’t even available on the Mercs. But for the buyer who liked performance with a luxury bent, there were some attractive offerings at the sign of the cat.

The 1966-67 Comet Cyclone GT is a good example of all these Mercury strengths and weaknesses. Comet jumped from a compact to an intermediate in ’66 thanks to its use of the new Ford Fairlane body shell. The cars shared a 116-inch wheelbase and, for all intents and purposes, had the same silhouette in both convertible and two-door hardtop form.


1966 Mercury Comet Cyclone GT
The Mercury Comet Cyclone GT was a good performer,
but wasn’t mean enough to win widespread respect on the street.


Despite the absence of an optional 427, the 1966 Comet Cyclone GT was no softy. Beneath the non-functional hood scoops sat Ford’s 390-cubic-inch High Performance V-8 with a four-throat Holley carb. As in the Fairlane GT, it was rated at 335 horsepower at 4800 rpm and 427 pounds/feet of torque at 3200 rpm. A 10.5:1 compression ratio and dual exhausts were part of the package, as was a higher degree of reliability than offered by the high-strung 427.

A three-speed manual transmission was standard; optional was a four-speed manual or the C-6 Merc-O-Matic three-speed automatic. New 1-2-D Sport Shift let the automatic-transmission’s driver change gears manually. A rear-axle ratio of 3.25:1 was standard, with optional ratios of 3.00:1, 3.50:1, 3.89:1, and 4:11:1 available.

Underneath, a heavy-duty suspension operated with stiffer spring and shock damping rates. Up front, a larger sway bar (15/16 inch) helped keep the body stable during hard cornering. Standard GT gear also included sporty stripes and an engine dress-up kit that consisted of a chrome air cleaner and valve covers. The standard tires were 7.75x14 whitewalls on 5.5-inch rims. Mercury offered optional hub caps that looked like chrome wheels without wheelcovers.

The Comet Cyclone GT was about $100 more expensive than its Fairlane counterpart. It had richer interior appointments that included a five-dial instrument cluster, plush bucket seats, and sculptured console. Power steering, power front disc brakes, and factory-installed under-dash air conditioning were optionally available.

Mercury got some valuable exposure for its Comet Cyclo GT when it was chosen as the official pace car of the ’66 Indianapolis 500. But on the street, where it counted, serious performance enthusiasts were favoring the likes of the Pontiac GTO, Chevy Chevelle SS 396, and big-block Dodge Coronet and Plymouth Belvedere. Actually, the ’66 Fairlane was one of the big winners in this segment, though only 37,343 were GTs. Cyclone GT production was 15,970. Pontiac, by contrast, built 96,946 GTOs that year.

Engine Type
V-8/FE Series
Displacement (cid)
Horsepower @ rpm:
335 @ 4800
Torque (pounds/feet) @ rpm
427 @ 3200
Compression Ratio
Bore (inches)
Stroke (inches)
Valve Lifters
1966 Cyclone GT


0-60 mph (sec)
0-100 mph (sec)
1/4-mile (sec)
13.98 @ 103.8 mph
Top speed (mph)
Axle ratio
Engine type

*Source: Car and Driver (1966)

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