My Car Quest

June 21, 2024

Mustang Boss 429 – American Muscle At Its Best

by Mike Gulett –

An American muscle car must have power and speed, at least speed in a straight line. I believe they should look good too. And if they have an interesting story or something that makes them special, like a unique engine (think Hemi) or built by a special person (like Carroll Shelby), then all the better.

The Mustang Boss 429 is one of the best of the American muscle cars with a very interesting back story. Made only in 1969 and 1970 in limited numbers (857 in ’69 and 500 in ’70 for a total of 1,357).

1970 Boss 429 Mustang

1970 Boss 429 Mustang

Ford needed to homologate the 429 semi-hemispherical engine for NASCAR racing of the Torino by making at least 500 cars with this engine and selling them to the public. The Mustang was chosen as the path to this homologation (why not the Torino?).

The Boss 429 engine came standard with a single Holley 4-barrel carburetor with ram-air rated at 735 CFM mounted on an aluminum intake manifold. The Mustang’s engine compartment was not wide enough to accommodate this engine, so Ford contracted with Kar Kraft of Dearborn, MI to modify the 4-speed Cobra Jet Mustangs so this engine would fit.

Ford Mustang Boss 429

That is a tight fit.

Kar Kraft was a Ford exclusive experimental facility that functioned as Vehicle Engineering for Ford’s Special Vehicles. Kar Kraft had previously developed the first GT40 MKII (winner of the 1966 24 Hours of Le Mans) and designed and built the GT40 MKIV (winner of the 1967 24 Hours of Le Mans).

Mustang Boss 429

According to The Auto Channel,

Partially completed SportsRoof Mustangs that were destined to originally receive the 428SCJ engine, were modified at Kar Kraft to accept the large 429 engine.

The main difficulty was getting the Boss 429 engine to fit the Mustang’s engine compartment. To do so, the shock towers were relocated outward (by hand) and while they were at it, the suspension was lowered and moved further outwards 1 inch, using spindles and control arms unique to the Boss 429. This made the Boss 429 handle much better than other big-block equipped Mustangs.

1970 Ford Mustang Boss 429

Other features included Boss 429 fender decals, manually controlled hood scoop, a front spoiler that was shallower than the Boss 302 spoiler, color keyed dual racing mirrors, engine oil cooler, trunk mounted battery, close-ratio four speed manual transmission 3.91 rear axle with Traction-Lok, 3/4 inch rear sway bar (the first Mustang ever to have a rear bar), chrome 15×7 Magnum 500 wheels with F60x15 Goodyear RWL Polyglas GT tires.

All Boss 429s came with the Deluxe Decor interior, 8000 rpm tachometer and AM radio.

The hood scoop is unique to the Boss 429 and is body color on the ’69 models and painted black on the ’70 models. This is an easy way to tell the difference between the two years.

The Boss 429 has an understated exterior compared to other Mustangs from the era. Only a small decal on the front fender identified this as a Boss 429 and the large hood scoop gave one a hint as well. But there were no stripes or other flashy graphics to indicate that this is a special Mustang. There was no A/C because there was no room in the engine bay and all Boss 429s had manual transmissions.

Wouldn’t this be a cool Muscle car to own and drive?

Ford Mustang Boss 429

1970 Boss 429 Mustang

1969 Boss 429 Mustang

Engine: 375hp Boss 429 V-8

Transmission: Four-speed manual

Axle Ratio: 3.91:1

Weight: 3,870 lbs

Acceleration (Seconds):

0-30 mph 3.2

0-60 mph 7.1

0-100 mph 13.6

Standing 1/4 mi 14.09 @ 102.85 mph

Top speed: 118 mph

Source: Car Life 7/69

Let us know what you think in the Comments.

1970 Boss 429 Mustang logo

Ford Logo

Mustang Boss 429 - American Muscle At Its Best
Article Name
Mustang Boss 429 - American Muscle At Its Best
The Mustang Boss 429 is one of the best of the American muscle cars with a very interesting back story involving an engine of course.


  1. Rob Krantz says

    Mike, always loved these and the Boss 302’s as well. I remember when you could pick up a Boss 429 in the 1980’s for $6,000 or so. Wish I had had the foresight!

Speak Your Mind