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Ford Mustang 1969-`70-The Boss 429

The Ford Motor Company developed an engine then they looked for the best place to put it for testing. The new power plant has a 429 cu in displacement and is based on the earlier Ford 385 engine. Four bolt main bearings with a forged steel crank-shaft and forged steel connecting rods are used in the engine blocks. Hydraulic lifters are in the 1969 models but for 1970 they have a camshaft with mechanical lifters and an upgraded dual exhaust system but both can still develop the same horse power. Passages for the oil and water are sealed with an “O” ring at each cylinder. The heads have a type of modified hemispherical combustion chamber that Ford calls “The Blue Crescent.” There is a Holly four barrel with a rating of 735 CFM bolted to an aluminum intake manifold. The valve covers are made of magnesium and these earliest engines are reputed to be more powerful than the later “T” and “A” code replacments. This engine is an experiment by Ford to produce a Hemi type power plant to rival the Chrysler 426 Hemi doing so well on NASCAR circuits. NASCAR homologation regulations at the time required that the engine be available in a minimum of 500 vehicles for sale on the retail market during each year.

Ford Mustang yellow1970© Wickedgood | Dreamstime.com - 1970 Ford Mustang Boss 302 Photo

The Mustang was the vehicle Ford chose to put the engine into and “Boss 429 Mustang” is the chosen moniker. For the two years that the 429 is in production there are a total of 859 units of the engine manufactured. Ford out-sourced the needed modifications on Mach I and Cobra Jet shells to Kar Kraft who were active in a number of Ford Mustang projects at the time. The engine compartment must be modified to accommodate the exceptionally large hemi block. Kqr Kraft shortens the front suspension mounts, widens the shock towers and extends the inner fenders to allow the block with exhaust manifolds to fit. There is no room for a battery under the hood so it is mounted in the trunk and a ridged ¾’ sway bar is added in the rear to beef up the handling of the front heavy car. The Boss 429 is the first Mustang fitted with a rear sway bar which improves the track performance greatly over any other big block Mustang model of that era. The engine has an oil cooler and the 3.9:1 rear axle is equipped with the “Traction-Lock” limited slip differential. The Hurst shifer is standard equipment in 1970 but because of the engines size no air conditioning is available for either year.

Ford Mustang rear1970© Kmm7553 | Dreamstime.com - Classic Ford Mustang Automobile Photo

The Boss 429’s all black interior features an 8,000 RPM tachometer, the AM radio and has a hand lever to operate the hood mounted air scoop which is the largest ever used on a Mustang. There is a front spoiler with a lower profile than the Boss 302 version and the two racing mirrors are color coded. No 429 came with factory installed rear window louvers
The 1970 model features an expanded choice of paint and sports matt black scoops on all body colors. There was an extremely rare six pack complete with intake and carburetors available as a dealer installed option but only two units were installed. There were 499 units produced in 1970 and can be worth in excess of $500,000.00 before restoration.

Ford Mustang white1970© Raytags | Dreamstime.com - Ford Mustang Photo

There were three different 429 engines manufactured during its two year production. The “S” code 429 is the first version and it is assembled with a host of high performance parts but it has warrantee issues, possibly due to incorrect assembly. The 429 engine is revised and the “T” code is the replacement with a host of lighter duty internal parts. Reaching the end of production the “A” code 429 is the last variation with a new valve train and more pollution control equipment than the earlier engines. All of the 429 power plants produced during the two years were very under rated at 375 hp (280 kW) but will have no problem producing 600 plus horse power with a little tweaking. The Boss 428 engine is highly regarded with each unit revised by Kar Kraft getting a NASCAR “KK” number placed on the driver’s door. The first unit produced has the number KK 1201 and the last is KK 2558.




3 thoughts on “Ford Mustang 1969-`70-The Boss 429”


  1. Ron Trainor says:

    Your research in all these cars is excellent!! Look forward each day to your site. There quite a few things I’ve learned and love it! Keep up the good work. You’re #1 in my book!

  2. The scoop may have been the largest on a production Mustang, but it suffered from air starvation issues at the drag strip. It was a flaw in the design and, NHRA S and SS rules being what they were, modifying the scoop was forbidden. On top of that the “S” code engines not only had heavy duty rods and such, they were NASCAR heavy (and the juice cam did it no favors either). All of which conspired to make unremarkable E.T.s at the strip (I can’t think of any Boss 429s that won at the digs in its day… Heck! I don’t even see them in the F.A.S.T. series). Granted, Ford later on rectified those engine issues, but did nothing to fix the scoop (which ended up being the car’s weak point). That engine/car combination should have been the HEMI’s worst nightmare. Ford seriously dropped the ball on that. I think that the BOSS 429 is the highest priced musclecar at auction that didn’t do that well at the strip.

  3. Garrett R Gustkkey says:

    I would like some facts about the Boss 426 Mach 1. when they came out there are one that was the baby blue with the rear spoiler and the rear window louvers. I saw a picture on this edition. of pictures. I would almost bet it is the same Car. The Boss 429 made to most authentic sound made except the SOHC 427. I am Mopar fan for sure but . Muscle Cars are the trip.The fastest was THE 427 NOVA ? big question mark. I would like resources to study every single option for every single Muscle car to be the Expert I want to be. Garrett(Shorty) Gustkey


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Ford Mustang 1970 Boss 302

In 1970, Trans Am racing was one of the hottest tickets going, and all the American automakers had a hand in the action.   This Candy Apple Red 1970 Ford Mustang Boss 302 is a beautiful example of the street version of Ford's Trans Am entry.


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Pontiac Trans-Am & Banshee Roots

North America weathered two major fuel crises in 1973 and 1979, which set the stage for the changes made to the Trans-Am beginning in the 1982 model year. The engineers at Pontiac had concentrated on aerodynamics for a reduction in fuel consumption. With the technology of the day, it was impossible to have powerful, high-torque engines that would conform to the EPA-mandated emissions control regulations. By integrating aerodynamics and reducing weight, the  new “F” body platform Trans-Am evolved. Pontiac used wind tunnels to design this platform so as to achieve the best results possible. A Trans-Am equipped with a four-cylinder engine achieved 34 miles per gallon. The engineers succeeded in building a fuel efficient package to work from; they created a vehicle with world class aerodynamics, excellent handling, and fuel economy.

1981 Trans Am 3

1981 Firebird

The Trans-Am for 1982, the third generation, received a complete redesign and was about 227 kg (500 pounds) lighter than the previous year. This new style had a windshield set at 62 degrees with a large rear window without a supporting frame on the storage area access door. Two hidden headlights in front, finned aluminum wheels covered by smooth hubcaps, and a functional rear spoiler complete the picture.

The Firebird was a success, at least for fuel economy, but sales dropped. Pontiac had to sell this car of the future to the public now as well as in the future. By 1989, the Firebird was much more desirable to the public, and Pontiac had the fastest production car made in North America at that time.

1981 Trans Am

1981 Trans-Am Firebird

The Pontiac engineers had the Banshee I concept car  in mind since 1964. It  existed in four different generations until the 1989 model year; the designers heavily integrated many of the ideas in this originally two-seat car into the designs of the second-, third-, and fourth-generation Trans-Am.

The first-generation Banshee exists today represented by two automobiles owned by private collectors. One is a silver hardtop with a straight six engine; the other is a white convertible V8. This was the original car Pontiac wanted; instead, the company decided on the pony car class Trans-Am. The high-performance Banshee taillights are the same as the first Firebird, while the third-generation Firebird had very similar body lines as this prototype.

The Banshee II (1968) had a fiberglass skin over stock Trans-Am panels. The wheel covers are flush-mounted; the hood had deep louvers. The 400-cubic-inch V8 engine powers the car, which is close to the ground with a low slung suspension.

The third-generation Banshee (1974) has a front hood and grille very similar to a later model Firebird. The car has a long slope in front with quartz/halogen headlights, covered and low, both to lower resistance and wind noise. The bumpers are soft-faced the same color as the body over an impact-absorbing foam. Pontiac showed a metallic maroon-colored Banshee III to the public in 1974, this one powered by a 455-cubic-inch V8.

1998 Trans Am - Copy

1998 Trans-Am G4

The Banshee IV, unveiled in 1988, was a two-door, four-seat-style coupe. The fiberglass body is red with a black matte hood, and power comes from a 230 horsepower, fuel-injected overhead cam V8 with rear-wheel drive. The car's computers used a heads up (HUD) instrument display, while the fuel level is displayed on the windshield in the driver’s field of vision. The dual rear spoilers are hydraulic and easily adjustable by the operator from the driver’s seat. This design strongly influenced the fourth-generation Trans-Am.

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1998 Trans-Am G4


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