Boss 429 Mustang

From Wikipedia, the free encyclopedia
  (Redirected from Boss 429)
Jump to: navigation, search
Mustang Boss 429
Manufacturer Ford
Production 1969–1970
Assembly Dearborn, Michigan
Engine 429 cu in (7.030 l) 385 V8
Transmission 4-speed manual
Length 187.4 in (4,760 mm)
Width 71.7 in (1,821 mm)
Height 50.4 in (1,280 mm)
Curb weight 3,870 lb (1,755 kg)

The Boss 429 Mustang is a high performance Ford Mustang variant that was offered by Ford in 1969 and 1970.


A Boss 429 engine

The Boss 429 (also known as the "Boss 9" by enthusiasts) is arguably one of the rarest and most valued muscle cars to date.[1] In total there were 1358 original Boss 429s made. The origin of the Boss 429 comes about as a result of NASCAR. Ford was seeking to develop a Hemi engine that could compete with the famed 426 Hemi from Chrysler in NASCAR's Sprint Cup Series (then known as "Grand National Division"). NASCAR's homologation rules required that at least 500 cars be fitted with this motor and sold to the general public. After much consideration, it was decided by Ford that the Mustang would be the car that would house this new engine.

The Boss 429 engine was derived from the Ford 385 engine. It used four bolt mains, a forged steel crank and forged steel connecting rods. The engine featured aluminum cylinder heads, which had a modified Hemi type combustion chamber which Ford called "crescent". These heads used the "dry-deck" method, meaning no head gaskets were used. Each cylinder, oil passage and water passage had an individual "O" ring style seal to seal it tight. The Boss 429 engine used a single Holley four barrel carburetor rated at 735 CFM mounted on an aluminum intake manifold that flowed well for its time. 1969 cars featured a hydraulic lifter camshaft while 1970 models got a mechanical lifter camshaft along with an improved dual exhaust system though rated power output stayed the same.

The Mustang's engine compartment however was not wide enough to accommodate the massive Boss 429 engine, as a result Ford assigned Kar Kraft of Dearborn, MI to modify 4 speed Cobra Jet Mustangs to accept the new Boss 429 Engine. Kar Kraft was a Ford exclusive contracted experimental vehicle facility that functioned as Vehicle Engineering for Ford Special Vehicles. Kar Kraft had previously developed the first GT40 MKII's and designed and built the GT40 MKIV's, both of which won the LeMans 24 Hour Race in France in 1966 & 1967.

Production of the Boss 429 began in 1968 at Kar Kraft's new assembly plant in Brighton, Mich; the cars were transported to this plant directly from the Ford Rouge plant and the work began. The new, revised, front apron assemblies that accepted the large Boss 429 engine had been installed by the Rouge plant as the base vehicles were being built, this produced a stronger and cleaner front structure for this special vehicle; the reworked front fenders were also installed at the Rouge plant.

[1] Next the battery was repositioned to the trunk and a stiff 3/4" sway bar was added to rear end to improve handling since the car was now nose heavy. This was the first Mustang ever fitted with a rear sway bar, and it notably handled much better than other big-block Mustangs of the time, making it a very capable track car. It came fitted with an 8,000rpm tachometer, and AM only radio. In addition, a hole was cut in the hood, and a manually controlled hood scoop was added to these cars. Other features included a front spoiler that was shallower than the Boss 302 spoiler, color keyed dual racing mirrors, and an engine oil cooler. It was also equipped with a 3.91 ratio rear axle with a "Traction-Lock" limited slip differential.

The cars were rated very conservatively at 375 hp (280 kW) and 450 lb·ft (610 N·m) of torque. Actual output was well over 500 horsepower (370 kW). Some people have claimed it to produce 600 or more horsepower, citing extensive testing to prove the results, though nothing has been actually proven. However, it is very easy to coax such power out of the semi-hemi engine due to it being factory de-tuned for street-ability purposes. These horsepower claims have been proven from many dynamometer test results over the years with factory stock engines; some rebuilt to factory specs, and others pulled directly from the cars themselves immediately after purchase, though specific output tends to vary per engine due to testing parameters. The 429 Drag Pack option from Ford at the time (which was a normal 429 SCJ and not the Boss version which made more power) had 495 horsepower (369 kW), which was quite impressive for the time, however it should be noted that these ratings were strictly engine crank horsepower, and not actual wheel horsepower figures. The manufacturers and dealers only listed 375 hp (280 kW) because of legal issues and rising insurance costs so customers would be lured into buying these cars without the stiff fees from an insurance company, though no manufacturer has ever stated this to be true, assumingly so to prevent possible lawsuits.[2] Despite the high horsepower and torque ratings, the car was at home in the high RPM range (the engine is said to be able to rev up to 9,000rpm for extended periods of time, which is impressive given the engines massive 7.0L displacement, though were factory limited to 6,200rpm for insurance purposes[citation needed]), and suffered a poor by today's standards 0–60 time because of this. However, it quickly made up for that once it got moving. The car unrestricted is said to be able to exceed speeds of up to 175mph, though no actual claim has been proven due to the rarity, value and collectibility of the car, making anyone who owns one reluctant to try it.

Both model years featured a toned down exterior, as compared to other Mustangs of the era (see Boss 351, Boss 302, Mach 1), in that the only external identification of the car were the Boss 429 decals on the front fenders and unique hood scoop. The rest of the car featured a very clean look that was atypical of most Mustangs that Ford had produced which could be deceiving to some people. Source:Don Eichstaedt,Resident Engineer Kar Kraft Brighton Assy.Plant - 1969/70 Kar Kraft - 1966/1970 Ford Motor Company - 1971/1991 To show just how special these cars were, they were given special NASCAR identification that was placed on the driver's side door. Each car was given a "KK" number which stood for Kar Kraft. KK #1201 was the first Boss 429 and KK #2558 was the last Boss 429 made.[1]

Unfortunately sales started to drop off for the 1970 Boss 429 Mustangs and with higher production costs, gas costs, and other internal Ford problems, it was decided that 1970 would be the last year of the Boss 429.

In present day, these cars are highly sought after. As of 2008, auctions on eBay and at Barrett-Jackson have brought bids of over $375,000. In 2013 a black 1969 Ford Mustang Boss 429 Fastback (unrestored) sold for $417,000 at Mecum's auction in Kissimee Florida. In 2016 a restored black 1969 Boss 429 sold for $500,000 at a Barrett-Jackson auction in Palm Beach, Florida.

1969 Model[edit]

In 1969 there were 859 Boss 429s made by Ford Motor Company. 2 of which were Cougars for Lincoln/Mercury Race Division. There were five different colors available in 1969 (Raven Black, Wimbledon White, Royal Maroon, Candy apple Red, and Black Jade), and the only color for the interior was black. The fully functional hood scoop was the same color as the car, and noticeably larger than anything else offered on any Ford product at the time, with the exception of the 2 Boss 429 Cougars. This scoop would carry over to the 1970 model year but would be painted black on all cars. To this day, it is the largest factory hood scoop ever installed on a factory produced Mustang. All these cars were a manual transmission, and there was no air conditioning available due to the size of the engine. Though not originally offered as an option, it is common to add a spoiler and window louvers commonly seen on 1969–1970 Mach 1's and Boss 302's. Some early cars were known as "S" code cars and as such had a slightly different engine. These cars had magnesium valve covers, NASCAR style forged internals, nearly no smog or emissions equipment and are said to be more powerful than the later "T" and "A" code engines which had the emissions related equipment to satisfy government regulations. The engines in some cases were removed from the cars for use in other applications such as tractor pulling, due to the extreme torque and horsepower the engine was capable of producing.

1970 Model[edit]

In 1970 there were 499 Boss 429s made by Ford Motor Company. There were five new exterior colors (Grabber Orange, Grabber Green, Grabber Blue, Calypso Coral, and Pastel Blue) and the interior was available in Black or White & Black. The hood scoops for this year were all painted matte black regardless of the color of the car. These cars also had a manual transmission and no AC was available, again due to the size of the engine. The Hurst Shifter was also standard equipment for this year. Also in 1970 there was an extremely rare dealer-installed option of a six-pack intake and carburetors, however very few of these were ever sold (approx. 2 were installed). It is unknown if these made any difference in performance, though highly likely.

See also[edit]


  1. ^ a b Marshall, Wal. "The Amazing Boss 429.[dead link]", 10 April 2008.
  2. ^ Strange, Stephen B. Boss 429 Performance Mustang Style (Revised Edition). Motorbooks International, ISBN 0-931417-02-3.

External links[edit]