The Ford Boss 429 Mustang, which first hit the road in 1969, has become a classic among fans of muscle cars. The purpose of the car however, was not to appease the fans. The Boss 429 Mustang was outfitted with a 429 CID V8 engine that Ford was planning to use for its future entrants in NASCAR, but racing rules said that at least 500 iterations of an engine must be produced and sold before it qualifies for stock car racing. And hence, the Boss 429.
All told, there were only 1,356 Boss 429 Mustangs ever produced. The production run was ended in 1970 and the model never really panned out to deliver incredible performance right off the showroom floor due to a number of reasons. First of all, the mammoth engine was fitted with a too-small carburetor. In fact, the Boss 302 model had a larger carb despite the smaller engine size. Also, the engine, because it was envisioned for NASCAR use, was specifically tuned to deliver power at the high ends of the RPM band and at higher speeds, meaning that the muscle car benchmark of the quarter mile was tough for the Boss 429, despite a listing of 450 lb-ft of torque.
The engine itself caused a few problems as well. The 429 had hemispherical heads that widened the engine considerably. Anyone who has ever looked under the hood of a 351-equipped classic Mustang can tell you that the engine didn’t leave much extra space in the engine bay, and the 429 left even less. You couldn’t get a Boss 429 Mustang with air conditioning as an option because the equipment literally could not fit into the car. Also, the battery was moved to the trunk and there was no option for an automatic transmission. There was an upside to this, however.
In order to handle the extra weight, and the extra size, Ford’s engineers had to revise the suspension geometry and alter the components. What resulted was a bit more complicated than the traditional Mustang suspension, but was in fact much better. The Boss 429 Mustang emerged from the factory as one of the best-handling stock muscle cars of the day, but people were looking for speed in a straight line in their muscle cars, and the car’s 375 horsepower didn’t really cut it.
And that’s where the tuners come into play. A few alterations, mainly including a new carburetor and revised engine tuning, will easily bump the 429′s output to 475 horsepower, and a bit more fiddling will get you to the mid-500s with a bit of patience and a lot of knowledge. These modifications will also widen the powerband, which was notoriously small on the stock 429 because, again, it was meant for the high-RPM NASCAR setting.
Tuners, in effect, are the lifeblood of the Boss 429 Mustang. Ford’s designers provided an incredible starting point that, had it been given time, could have developed into one of the best muscle cars on the road. Some changes to the engine would have given it more power than most any other car on the block, and the impressive (at the time) handling would have kept you cruising on the road while other dragsters had to slow down to 45 mph in order to take a turn without flipping over.