Original Boss: A Boss 429 With Correct Parts And A Few Extra Cubes

Many “vintage” engines are revered for what they were when the debuted. Often times, as technology evolves, their impressiveness, relatively speaking, changes. However, what won’t ever change, are the impressions left when they were the king of the hill. That is exactly what happened with Rick Stanton and the Boss 429.

After sitting in a Boss 429 Mustang at the dealership in 1969, with a Talladega sitting right next to it, Stanton vowed to have a Boss 429-powered Talladega one day. What followed was almost half a decade of parts collection, with the desire to build an engine that used as many original parts as was feasible, with a few minor adjustments here and there to reach the ultimate goal of 800-plus horsepower in a streetable combination.

“I wanted a NASCAR car to drive on the street, but with all real NASCAR parts,” Stanton says. “I wanted period-correct pieces as I wanted a period-correct Talladega as they were raced, except I couldn’t leave the engine alone with only 600-650 horsepower.” So to that end, Stanton took all his accumulated parts and put together a big-cube Boss 429 engine.

Slight Artistic License

Starting with a Ford A460 iron block as a base, Stanton went way beyond the original 429 cubic-inch displacement n the Boss 429 engine. The A460 block comes with a 4.340-inch bore out of the crate, but Stanton took the cylinders out to the recommended maximum bore, and then added another .015 inch, for a total bore diameter of 4.615 inches.

The max listed stroke for the block is 4.500 inches and Stanton intended to use every bit of that clearance, but went about it in a unique way. Stanton acquired a Can-Am 494 crankshaft from Holman & Moody in the early 1970s (a pair of them, actually) with its standard 3.85-inch stroke.

While the pistons and rods might not be vintage, the crank in the short-block sure is. After purchasing two forgings back in the early ’70s, Stanton had one offset-ground to turn the traditional 3.85-inch stroke into a 4.500-inch throw.

He then had the rod journals offset-ground to get a 4.500-inch stroke length, making for a total of 602 cubic inches of displacement. A set of Eagle 6.800-inch attach to the rare crankshaft, thanks to the 2.200-inch journal diameter and ARP L19 bolts. The small end uses .990-inch wrist pins to keep the pistons attached to the rods.

Using custom Ross flat top pistons, compression is solidly in the double digits, while a set of Sealed Power HellFire piston rings keep the combustion in the cylinder and the oil out of it. Aiding in that task is a factory NASCAR aluminum dry-sump pump and original two-piece dry-sump oil pan, with two scavenge and one pressure stage.

Continuing the vintage parts theme, this original magnesium two-piece dry-sump oil pan features an original three-stage (two scavenge, one pressure) pump as well.

Topping off the short-block is a set of factory NASCAR C9AE-C PD cylinder heads with the D-port intake ports and raised exhaust ports, both of which have been port-matched. The cylinder heads feature the full-hemispherical 105cc combustion chamber, which houses a 2.400-inch intake valve and a 1.910-inch exhaust valve, with stems .100-inch longer than stock. The ports flow 441cfm at .750-inch lift on the intake side, and 330cfm on the exhaust. “These heads are the last of the development of the Boss 429,” explains Stanton.

Controlling those valves is an Isky Camshafts solid-roller cam, featuring 268 degrees of intake duration, 272 degrees exhaust — both at .050 inch — with .748 inch of lift at the valve. A set of Crane Ultra-Pro solid roller lifters ride the cam lobes and move a set of Manton 3/8-inch pushrods. The pushrods then actuate the factory NASCAR forged 1.75:1-ratio rocker arms, which have been polished to reduce friction. A traditional double-roller timing set keeps the camshaft and crankshaft in sync.

These C9AE-C heads were the final revision of the Boss 429 platform. With the minor porting Stanton has performed, they have some incredibly stout flow numbers. The engine’s 602 cubic inches move a lot of air.

It’s All About Induction

Providing the combination with the all-important air and fuel is an original NASCAR Spider single-plane intake, topped off with a single 1,250cfm Dominator carburetor. The carb is fed a diet of 100 octane gasoline by a mechanical fuel pump system typical of NASCAR of the time, and an original NASCAR magneto ignition system is used to keep the candles lit.

In addition to the original single-plane spider intake, Stanton also has an original “Torque Box” intake manifold, that was popular with NASCAR teams on short tracks and road courses for the much greater low-end power they offered. Because he has both intakes, as well as a healthy curiosity, Stanton decided to test both of them on the dyno.

First up was the single-plane spider intake. Setting the dyno for a 4,000 to 6,800 rpm sweep, the initial power numbers peak at 6,500 rpm with 869.7 horsepower. Torque for the pull started significantly lower than the peak, but by 4,700 had peaked at 785.0 lb-ft. The next pull, with the torque box intake, showed a significantly different curve shape.

The original 1.75:1 rocker arms are typical of a NASCAR engine of the time, and have been polished to reduce friction and shed oil.

The second intake manifold posted peak numbers of 809.8 lb-ft of torque at 4,500 rpm and 818.8 horsepower at 5,800 rpm. While the peak torque numbers sound close, when you look at the peak horsepower numbers and locations, you start to see something is off. Once you look at the graphs instead of the numbers it becomes readily apparent why the torque box intake was preferred for situations where you spent significant time in the midrange.

From 4,000 to 5,000 rpm (on the graph; presumably, the trend continues below 4,000 rpm) the torque box intake has a distinct advantage over the single-plane until the first power drop around 5,000. The two graphs cross but stay close to one another until the 5,600-to-5,800-rpm range, falls off (again) significantly, resulting in a 94 horsepower and 78 lb-ft difference at 6,800 rpm.

Differences in numbers aside, this enlarged Boss 429 engine is making a significant amount of steam without a lot of apparent mechanical effort. Of course, it’s being asked to perform for significant periods of time in varying conditions while on the road courses in Stanton’s ’69 Talladega.

“The torque box intake has so much more torque that, at Willows Springs running laps and having a blast, I was having a problem with breaking the tires loose at any speed on the track,” Stanton says. “I would come out of a corner and get into it, it would start smoking the tires — even on the front straight. I was doing about 120 mph and the car would get loose, get a little sideways. I’d back out of it, squeeze it again and it would break the tires loose again.”

It’s really cool to see an engine built with 50-year-old parts still putting in work and making great power, all while actually being used, as opposed to sitting on a shelf somewhere collecting dust.

Here you can see the dyno graphs of the engine running the two different intake manifolds. The graph in the middle is the "Torque Box" intake popular on road courses and short tracks in the '70s, while the graph on the right is the single-plain "spider" intake, which obviously performs much better up top, was popular at the super-speedways. The graph on the left is the two overlaid for a direct comparison of powerbands.

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About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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