Mercury Cyclone GT

Cyclone GT at a glance

The 1966 Comet Cyclone GT and the Indy pace car

For 1966 Mercury moved the Comet onto the body of the Ford Fairlane, and the Cyclone became its sporting top line. The GT option brought the S-code 390 with a Holley four-barrel and 10.5:1 compression, a fibreglass bonnet with two scoops and body stripes. The axle was 3.25:1 as standard, with 3.00:1 optional.

A Cyclone GT convertible paced the 1966 Indianapolis 500, the only time a Mercury did so in the modern era according to Over-Drive magazine's fact sheet. The GT was clearly the version buyers wanted: Mercury built 13,812 GT hardtops and 2,158 GT convertibles against 6,882 plain Cyclone hardtops and 1,305 convertibles.

For 1967 the formula carried over, with the 390 quoted by Wikipedia at 239 kW (320 hp). Total Cyclone output fell to 6,910 cars, 809 of them convertibles; no reliable GT split has been published for that year.

A fastback body for 1968

Mercury dropped the Comet name from the Cyclone for 1968 and gave it the new Torino-shaped intermediate body as a fastback and a notchback hardtop. The GT added an upper body stripe, bucket seats, wide whitewall tyres, special wheel covers, an all-vinyl interior and the handling package.

Sources differ on the GT's standard engine that year. Hagerty says the GT lost the 335 hp 390 as standard and started with the 302 of 157 kW (210 hp); Wikipedia lists the 390 as standard on the GT at 198 kW (265 hp) or 242 kW (325 hp). The engine list itself is not in dispute:

Mercury built 13,628 Cyclones of all kinds for 1968. On the track, Mercury Cyclones finished first and second in the 1968 Daytona 500.

1969: GT as a package, CJ as the muscle car

For 1969 Mercury split the roles. The Cyclone CJ, at US$3,207 according to Hagerty, carried the 428 Cobra Jet with 250 kW (335 hp), optional Ram Air and a 3.50:1 axle, and was aimed at the Plymouth Road Runner. The GT became an appearance and trim package; Wikipedia lists a 390 of 239 kW (320 hp) among its engines that year.

That split matters to collectors. A 1969 car with GT badges does not have to be a big-block car, and 3,261 of the year's 9,143 Cyclones were CJs. The aerodynamic Spoiler and Spoiler II models of the same year have their own history.

1970: concealed headlamps and the 429

The 1970 Cyclone was restyled together with Ford's new Torino, and the GT was the version with concealed headlamps, a non-functional bonnet scoop and full-length lower body mouldings. Its standard engine was a two-barrel 351 Cleveland with a three-speed manual, rated at 186 kW (250 hp) by Hagerty. That made the GT, at US$3,025, slightly cheaper than the base Cyclone at US$3,035, which came with a 429 four-barrel of 268 kW (360 hp).

GT buyers could order the 429 in several forms, the four-barrel 360 hp unit, the 429 Cobra Jet at 276 kW (370 hp) and 610 Nm (450 lb-ft), and the Super Cobra Jet with the Drag Pack at 280 kW (375 hp), all SAE gross. Four-speed manual and automatic gearboxes were optional.

The GT was the volume Cyclone of 1970. For 1971 the car was folded into the Montego line, and after that year the Cyclone name lived on only as a Montego option, with 30 cars built for 1972.

Cyclone GT today: what to check

The first document to ask for is a Marti Report, which decodes the original build from Ford's records. It shows engine, gearbox, colour and options, and it matters because many cars have been re-engined: Autoevolution described a 1970 GT in October 2026 whose Marti Report lists the N-code 429 with a close-ratio four-speed, a combination found on 192 cars, but which now has a 545 cu in engine and a different colour.

• Engine codes: the S-code identifies the 1966 GT's 390 four-barrel; on 1970 cars C-code is the 429 Cobra Jet and N-code the 429 four-barrel without Cobra Jet parts.
• 1969 badges: a GT emblem alone proves nothing about the engine; CJ cars carry the 428.
• Pace car claims: 1966 convertibles are often sold as pace cars; ask for documentation, because the number of cars built for the race and for dealers is not well recorded.
• Values: in the same October 2026 article Autoevolution wrote that ordinary 1970 Cyclones rarely exceed US$30,000, while some manual GT cars sell for more than US$50,000.
• Trim: the 1970 option list included an Action Special Equipment Package with a bench seat; Wikipedia gives 953 cars, conceptcarz 933.

For the full model line see the Mercury Cyclone history, and for the NASCAR cars the Cyclone Spoiler II. The GT's Ford twin was the Ford Torino, and Mercury's pony-car sibling with the same 428 was the Cougar Eliminator. The Mercury catalogue lists the remaining models, and the muscle car guide sets the Cyclone among its rivals.

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