What is the 428 Cobra Jet engine described in this 1968 article?

The Cobra Jet is a mixture of Mercury's two big engines: the regular mass-production 428 block and internals combined with the race-bred 427 cylinder heads and manifolding, topped by a huge four-barrel carburetor.

How quick was the 1968 Mercury Cyclone 428 Cobra Jet in testing?

Quarter-mile runs were in the low or mid-14s with trap speeds in the high 90s, and the Cyclone reached 60 mph in 6.2 seconds—one of the quickest full-size production cars on the market at the time.

How much did the Cobra Jet package cost?

The article cites a $306 tag on the Cobra Jet package, which included stronger springs, shock absorbers, and a handling kit along with the engine.

What rear axle ratio did the test Cyclone have and what were its drawbacks?

The test car had a 3.91:1 rear axle ratio, ideal for the dragstrip but a nuisance elsewhere—at 70 mph the engine turned almost 4000 rpm, hurting gas mileage and potentially engine life.

What tires were fitted to the test Cyclone?

Goodyear's new Polyglas tires, a combination of bias plies and a fiberglass belt under the tread, which the article says delivered all the horsepower right from the start.

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1968 Mercury Cyclone 428 Cobra Jet Road Test - Car Life July 1968, Page 17

Magazine article page with text columns and a side photo of a Mercury Cyclone

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Scanned magazine article page about the Mercury Cyclone with prose columns and a side-profile photo.

AI caption July 2022 · Photo 481 of 486

This is page 17 of the July 1968 issue of Car Life magazine, part of a road test article on the 1968 Mercury Cyclone equipped with the 428-cid Cobra Jet V-8. The article explains that the Cobra Jet engine combines the mass-production 428 block and internals with race-bred 427 cylinder heads and manifolding topped by a four-barrel carburetor, and that the $306 Cobra Jet package includes a handling kit, beefed-up automatic transmission, and front disc brakes. Performance data cited includes quarter-mile times in the low-to-mid 14s with trap speeds in the high 90s, 0-60 mph in 6.2 seconds, and a 3.91:1 rear axle ratio that had the engine turning nearly 4000 rpm at 70 mph. The article praises Goodyear's new Polyglas tires (bias plies with a fiberglass tread belt) for putting the power to the pavement, discusses the car's understeer and highly controllable cornering behavior, and notes an initial rear-axle problem caused by loose axle-housing bolts that was corrected during testing. A photo shows the Cyclone on a road course, with a caption highlighting its near-neutral handling and race-car-like controllability in a street car.

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Frequently asked questions

What is the 428 Cobra Jet engine described in this 1968 article?: The Cobra Jet is a mixture of Mercury's two big engines: the regular mass-production 428 block and internals combined with the race-bred 427 cylinder heads and manifolding, topped by a huge four-barrel carburetor.
How quick was the 1968 Mercury Cyclone 428 Cobra Jet in testing?: Quarter-mile runs were in the low or mid-14s with trap speeds in the high 90s, and the Cyclone reached 60 mph in 6.2 seconds—one of the quickest full-size production cars on the market at the time.
How much did the Cobra Jet package cost?: The article cites a $306 tag on the Cobra Jet package, which included stronger springs, shock absorbers, and a handling kit along with the engine.
What rear axle ratio did the test Cyclone have and what were its drawbacks?: The test car had a 3.91:1 rear axle ratio, ideal for the dragstrip but a nuisance elsewhere—at 70 mph the engine turned almost 4000 rpm, hurting gas mileage and potentially engine life.
What tires were fitted to the test Cyclone?: Goodyear's new Polyglas tires, a combination of bias plies and a fiberglass belt under the tread, which the article says delivered all the horsepower right from the start.