The History of the Boss 302 Mustang

The History of the Boss 302 Mustang

Last Updated August 10, 2020

With only four letters and three numbers, Ford created a legend. Even if you don’t know the details, as a Mustang enthusiast, you certainly know the name Boss 302. You have to go back a few decades to discover the first edition, which came out in 1969. Despite only lasting two model years, the original Mustang Boss 302 blasted into the automotive history books leaving two smoking tire marks that are still there today.

The Boss 302 is one of the most legendary special-edition Mustangs. As the name suggests, the heart of the car was a 302 cubic inch V8. Though to be fair, the 302 wasn’t designed to fit in the updated 1969 Mustang. The ’69 was designed to fit around the 302. The Boss 302 story is an exciting one, and any enthusiast can appreciate the dedication and vision that went into creating this beloved sports car legend.

When the Boss Tells You to Do It, You Do It

So how did the Boss 302 get its name? While the ‘Boss’ label makes perfect sense for a car that dominated the competition, the name actually came from a more literal meaning. Larry Shinoda, the man credited as the designer of the Boss 302, was once asked about what project he was working on. To keep the project a secret, he simply responded “the boss’ car.” This clearly struck a chord, as the car was baptized ‘Mustang Boss 302’ when it hit the market in 1969. It was based on the newly redesigned Mustang but was created with a very specific mission.

Its mission involved the phrase ‘race on Sunday, sell on Monday,’ and it’s the reason the 302 came to be. Rules in the SCCA (Sports Car Club of America) racing league stated that a manufacturer had to sell a production version of any car entered to race in the Trans-Am series. Ford had no choice but to come up with a production version if they wanted to race a high performance ‘Stang.

This was important to Ford, especially since the 1967 Chevrolet Camaro was available with more powerful V8 engines than the Mustang — it had also won the 1968 Trans-Am racing series. There was no way they were going to be outdone by the newcomer, so Ford devised a plan to create an all-out performance Mustang. But it was going to take some creativity.

A Tale of Two Cities

A Ford racecar for the Trans-Am series was going to need an engine. However, Ford’s most recent attempt at a high-performance engine, the ‘tunnel port’ Windsor V8, had resulted in a disappointing racing year for Ford. At the same time, work had started on a new 351 cubic inch engine that would be built in Cleveland and bear that name.

In a true case of the sum of the parts being greater than the whole, Ford engineers combined the Windsor block with the Cleveland heads, and ended up with the Boss 302 engine for the Mustang. The strengths of these two components created a stout, powerful racing engine that would be responsible for turning the Mustang into a winning racecar that would take the Trans-Am series title in 1970.

The process involved much more than a case of simply throwing together a pair of heads and a block and calling it a day. The 302 engine was actually the first use of the Cleveland head design, which wouldn’t see regular production for a few years. However, Ford’s forward-thinking engineers were convinced that the larger heads could be mated to the small-block Windsor so they found a way to make them work together.

One significant feature of the 302 was that the heads were ‘oversized’ relative to the block, and much larger than the competition’s heads. The result was a heavy, over 500-pound engine that compensated with impressive power. The stats were impressive for the era:

  • 302 cubic inch ‘Windsor’ small-block V8, with 4-inch bore and 3-inch stroke
  • Modified ‘Cleveland’ cylinder heads, with 2.23 inch intake valves and 1.71 inch exhaust valves
  • Unique mechanical cam with ‘high-lift’ design
  • Crankshaft made out of forged steel and balanced both statically and dynamically
  • Holley 780 cubic feet per minute carburetor breathing through an aluminum intake

The official stats for the production 302 were 290 bhp at 5,800 rpm and 290 lb-ft at 4,300 rpm. Insurance companies were quick to target high-power engines, so it wasn’t uncommon for manufacturers to underrate the engines in their sports cars. The Boss 302 engines installed in the track versions of the Mustang were accurately listed at 470 horsepower.

Dealing With All That Power

Boss 302 Components

  • Suspension — Heavy-duty front coils and rear leaf springs were installed to make the 302 competition-ready. To prevent the dreaded wheel-hop that can hamper a car’s ability to get off the line quickly, staggered heavy duty rear ‘Gabriel’ shocks were used. To stiffen the handling, a 0.85 inch sway bar was used in front. Power assist was also added to the front disc / rear drum setup.
  • Transmission — Two transmission options were offered, a wide-ratio 4-speed (code 5), and a close-ratio 4-speed (code 6). Both delivered their power to one of four rear ends: the A code (open) 3.50:1, the S code (Traction-Lok) 3.50:1, the V code (Traction-Lok) 3.91:1, and the W code (Detroit no-spin) 4.30:1.
  • Wheels — The wheels used were Magnum 500 chromes, and featured a silver center cap. The rubber was F60x15 bias-ply, chosen with the track in mind. Raised white letters gave the look that we have come to associate with racing tires.
  • Exhaust — New manifolds were designed specifically for the 302 in the Boss Mustang. Cast-iron manifolds that fed into a transverse muffler system helped give the Boss its unique and revered exhaust note.

The end result was a dedicated sports car with all the credentials to take on the Trans-Am racing circuits. And while a ‘deluxe’ interior was added, not many creature comforts or options were included. This car had one purpose: make it around the track faster than any other car.

Entering the History Books

With the Boss 302 engine and the other necessary upgrades, the Mustang brand was finally ready to compete. The 1968 Trans-Am series was taken by the Chevrolet Camaro, and that didn’t sit well with Ford, who had created the whole pony car class several years prior. There was no doubt that the 302 was meant for the track. The Boss 302 engine provided some impressive performance stats:

  • Acceleration of 0-60 mph in 6.9 seconds
  • Quarter mile speed of 14.6 seconds at 98 mph
  • Top speed of 118 mph

The Ford team was led by Bud Moore, and while they failed to win in 1969, two Boss 302 Mustangs were entered in the 1970 season. One of them, driven by Parnelli Jones, pulled off a win and took the SCCA Trans-Am Championship. Having made its mark, the Boss 302 Mustang disappeared after a short two-year production run, leaving a place in the lineup for the 429 to be the torch-bearer for Ford racing.

The Boss 302 Engine

Boss 302 Mustang Engine

The 302 engine had several additional performance features that made it perfect for a race engine:

  • The block was strengthened with a thicker deck and 4-bolt main caps, and used a high nickel-content steel.
  • The big Cleveland heads used 8 valve cover bolts instead of six, and featured a wide intake manifold.
  • Connecting rods were forged from high-strength steel to support the high RPMs of the Boss.
  • The cross-drilled crankshaft was made of high-strength steel.
  • Small Autolite sparkplugs were used due to the large valves taking up space.

These design features combined to create what has become one of the true American performance legends. More than 40 years later, collectors and enthusiasts still hold up the Boss 302 as a perfect example of a street-legal racecar — and the price of these rare cars on the used-car market prove it. It was the solid lifter design that produced that distinctive chatter that still gets fans’ heartbeats racing fast today.

More Developments

The Boss 302 Mustang may only have lasted two years, but there were a few differences between the 1969 and the 1970 models.

The 1969 Boss Mustang featured several exterior upgrades relative to the standard Mustang, including front and rear spoilers. A C-shaped stripe on the sides made the car easily identifiable, along with the deletion of the fake rear fender scoops that were present on other 1969 ‘Stangs. Only a few options were available, including a blacked-out hood and a rear window shade that added to the racy look. Just under 2,000 examples of the Boss 302 would be sold in 1969.

Boss 302 Grille

For the following year, the Mustang front end was modified, going to single headlights on each side within the grille while adding vents in the previous outboard light positions. Two L-shaped stripes were also added to the hood. Beyond these cosmetic changes, a standard Hurst shifter appeared, as did a modified competition suspension and the dual exhaust system. Under the hood, the original chrome valve covers were swapped out for aluminum versions, while the intake valves were reduced in size. Over 7,000 units of the second year Boss sold.

SCAA rules stated that at least 1,000 copies of each car be sold per year, and the Boss 302 Mustang easily met that goal. The traffic the Boss drove into Ford showrooms was even more important. Already an unquestionable success, the new race-bred Mustang helped ignite the new breed of Mustang fans that exists to this day. Subsequent generations of Mustangs became legends in their own right and developed huge followings. This created a need for aftermarket support, which is where CJ Pony Parts comes in.

The Drop-In Boss Option

Boss 302 Mustang

Having been produced over 40 years ago, and only ever in low numbers, finding a Boss today isn’t easy. Thankfully, enthusiasts have kept the remaining examples in beautiful shape, and there is a lot of respect for an original Boss 302 Mustang. If you happen to own one of these rare beauties, you know how hard it can be to find parts to keep it in original, showroom condition.

A car like the Boss begs to be driven, and parts eventually wear out and need to be replaced. CJ Pony Parts carries a full lineup of parts for all of the popular Mustang models, including the Boss 302.

Finding an original 302 V8 replacement engine is also nearly impossible today, and even if you could, it would likely require significant repairs and upgrades to get it back into race-quality condition. Your best option is a crate motor, and CJ Pony Parts has a drop-in Boss 302 engine that gets the job done. When you turn the key after your install, you’ll even hear the classic sound that is a key component of the Boss appeal!

What if you’re not blessed with an original Boss Mustang? Nothing is stopping you from building your own! A crate engine is a great choice when you’re upgrading or modifying a Mustang, and the Boss 302 from Ford Racing is a popular choice for an ultimate performance ‘Stang. The specifications of the Z363 crate engine are impressive:

  • Based on the 302 small-block Ford block (8.2 deck), with a displacement of 363 cubic inches
  • Develops 500 horsepower at 6500 rpm and 450 pound-feet of torque at 5300 rpm
  • Piston dimensions of 4.125 inches bore by 3.400 inches stroke
  • Forged internal components (including the pistons, connecting rods, and crankshaft)
  • Unique Ford Racing ‘Z’ aluminum cylinder heads
  • Black wrinkle finish cast aluminum heads with Boss script

The engine is internally balanced, and it makes more than 50 hp and 50 lb-ft of torque than the Z347 it replaced in Ford Racing’s lineup. A high-performance oiling system keeps the engine lubricated as it revs up to 6500 rpm.

If you’re looking into a Boss 302 crate engine, you need all the dimensions, measurements and values for camshafts, rockers, and cylinders. CJ Pony Parts provides this information along with pictures, so you’ll know exactly what you’re ordering.

Building a Custom Boss

While the crate engine is a popular and easy ‘drop-in’ solution, some enthusiasts are looking for something a little more customizable. If you’re rebuilding your Mustang but want more flexibility, a new block might be the best starting point. Any original block, even on a well-cared-for Mustang, is going to be showing signs of wear. The Mustang was a pony car that was designed to be driven, and most examples of the 1960’s and 1970’s Mustangs are showing their age after decades of burnouts and drag races.

Even a solid traditional steel block like the reliable Mustang small-block will eventually need to be replaced, especially if you’re upgrading the performance. CJ Pony Parts offers over a dozen different blocks for all generations of Mustangs. One of the most exciting is obviously the Boss 302 block. Use the legendary Boss block and build up the exact engine you want for your Mustang project. The details will inspire you:

  • A 4.125 inch bore capacity, finished to a 4.115 inch rough bore
  • Maximum stroke up to 3.400 inches
  • Machined tolerances to allow factory lifter guides and retainers
  • Revised oiling and cooling system for better lubrication and heat management

You’re starting with a block that respects the original Boss design but has been improved with modern technology and materials. It offers an even more robust and flexible starting point for your engine build!

The Legend Continues

2013 Boss 302 Mustang

Ford realized that the appeal of the Boss name was as strong as ever, which is why they reintroduced it as a model of the fifth-generation Mustang. Available as a special edition model in 2012 and 2013, the Boss 302 once again carried a V8 — this modern version developing 444 horsepower and 380 lb-ft of torque.

Taking things one step further, there was also a Laguna Seca version of this new Boss, which added suspension and interior enhancements on top of the already capable Boss modifications.

While the Mustang is without question one of the most successful and respected American sports cars of all time, the Boss 302 version stands out as an example of the best of American engineering and design. Few cars with a short two-year production run have left such a mark on the performance landscape, which is why we’re still talking about the Boss today!

The History of the Boss 302 Mustang

While the Mustang is without question one of the most successful and respected American sports cars of all time, the Boss 302 version stands out as an example of the best of American engineering and design. Check out the history of the Boss 302 Mustang and see how it made such a lasting mark on automotive enthusiasts today.