The Boss 429, quite literally, is the boss! The Boss 429 is the largest engine that Ford ever offered, and it was available in the 1969 and 1970 Ford Mustang models. They were attempting to qualify for Nascar and Nascar’s rules required that at least 500 of these cars be manufactured and sold to the general public. Ford now had the task of creating a street car, that could compete in Nascar. The Boss 429 was an answer to the challenge! The Mustang Boss 429 contained a 429cid hemi-head V-8 engine. The engine was so big that the suspension had to be modified and the battery was moved to the trunk. It was advertised at 375 hp, but if it was carefully customized it was capable of exceeding 500 hp.
Ford drew attention to the Boss 429 model by including the biggest hood scoop placed on a production Mustang, complemented by a front spoiler that was similar to the Mach 1. It also came with magnesium valve covers.
Built for the sole purpose of allowing FORD to satisfy the NASCAR homologation rule for Grand National racing. To say that FORD built the car is a stretch. FORD actually only built part of the car. The Mustang soon to be a BOSS 429 was partly assembled at the FORD Rouge plant and then shipped to Kar Kraft in Brighton Michigan. The Rouge plant refused to ship an enginless car so they installed a 428 Cobra Jet engine in every car. The cars once they arrived at Kar Kraft were then partially stripped, Engines removed and discarded or actually stored nearby. They worked their magic modifying the frame and body installed the 429 engines and other parts, then shipped the car back to FORD for completion. Later on, FORD had a 428 Cobra Jet engine shortage and KarKarft sold the discarded engines back to to them!
The Once there, Kar Kraft made the suspension and body modifications, installed the 429 engine. Some of the modifications made by Kar Kraft were to move the spring towers forward 1 inch, lowering the A-arms 1 inch, flare the front fenders to make room for the F60 x 15 tires. They installed the engine, all the engine parts, trunk mounted battery, power steering cooler and oil cooler. There were 859 Boss 429 adrenalin pumping, neck snapping speed demons looking for a sucker to race in 1969, however in 1970 the added another 499 of these powerful beasts.
On the interior the Boss 429 was equipped with the Interior Decor Group, High back bucket seats, the visibility group which included parking brake warning light, glove box lock, luggage compartment light, ash tray light and glove box light and a lighted ignition switch. The Boss also received deluxe seat belts with a warning light, a console, Two special knobs to control the manual choke and the ram air vent door. Finishing off the interior was the optional instrument gauge cluster with a tachometers.
On the exterior, the Boss had its Boss had a large color coordinated manually controlled hood scoop installed on the hood, a 429 logo inconspicuously placed where the mustang badge usually appeared behind the front wheel well. Colors you could buy the Boss 429 in were Royal Maroon, Raven Black, Candyapple Red, Wimbledon white, Black jade and Blue. The front spoiler was shorter than the one used on the Boss 302 to gain clearance because the car was lowered.
FORD mated the engine to a 4 speed transmisson and a traction-loc 3.9:1 rear differential. The boss 429 engine was either the 820-T or 820-A series. They used a mechanical lifter/camshaft setup. The “A” version was fitted with limited emissions modifications.
All Bosses had the consecutive unit serial number stamped on the engine block for additional identification purposes. Boss 429’s had additional VIN numbers on the engine block, inner fenders and transmission. The Boss cars are the only mustangs that can match the original engine with the original car. Each Boss 429 received a KK sticker on the drivers door above the Ford sticker. They were numbered KK NASCAR 1201 through KK NASCAR 2059.