Nevertheless, in the mid- and upper ranges of the rpm band, this new-century Boss engine performed admirably. Brown and Lohone experimented with camshafts, header designs, and more on the dyno at Jim Kid Motorsports (www.jimkidmotorsports.com), in a give-and-take learning session that saw peak horsepower and torque numbers vary widely. The best result they saw delivered 670 peak horsepower at 6,400 rpm and 556 lb-ft of torque at 5,600 rpm, with 32 degrees of total timing.
"It's a hell of a street engine, no question about it," said Lohone. "From 3,500 rpm to 6,500 rpm--right where you want a street engine to perform--it pulls strong and smooth. It ought to put a '69 Mustang easily into the 10s."
Despite their engine's more-than-respectable performance, Lohone and Brown were left wanting more from it.
"Ford had a great design with the Boss 429 heads, but they were never used anywhere near their potential on the street," says Brown. "As the dyno results show, our procedures helped bring out more of the power, but there's still a lot left in there--and a roller cam would have easily pushed horsepower past the 800 level." The builders proved their point with this project, realizing much of the pent-up potential the original engine packed under its distinct valve covers. Next step: The Boss 529!
Quick History: Early vs. Late Boss 429s
There were two versions of the Boss 429 production engine, both rated at 375 horsepower. An updated engine was introduced during the '69 model-year run with changes designed to boost its anemic feel. Starting around the assembly of car No. 0280--still within the '69 model year--a higher-lift, solid-lifter cam from the 429 SCJ engine replaced the smaller, hydraulic camshaft that was installed at the start of production. The rod fasteners were also changed to ARP cap-style bolts.
The update delivered slightly better low-speed characteristics, but didn't radically alter the car's performance. Ford also specified a shorter, 3.90 axle ratio that also improved low-speed acceleration. The early, hydraulic-cammed engines are recognized by an 820-S engine code and magnesium valve covers, while the later engines (the vast majority of production models) had an 820-T code and aluminum valve covers.
A Badass Boss Project
In the nondescript shop for his concrete business, enthusiast Tom Marcucci is working on an interesting Boss 429-based project--he's shoehorning the engine into a classic '72 Gran Torino fastback. Purists may cringe to learn the project car is a virgin, 20,000-mile car in beautiful, unrestored condition, but that clearly doesn't bother Marcucci, who's plowing ahead with the swap. Although the assembly isn't an original Shotgun engine, the heads are original Boss '9 parts. The plan is to back the engine with a T-56 six-speed. Not surprisingly, Marcucci cites the need for scratch-built headers among his biggest challenges. We plan to check the progress of the project and grab some shots when his Boss Torino hits the street.
19 A Quick Fuel-built 1,050-cfm...
19 A Quick Fuel-built 1,050-cfm Dominator carburetor flows much greater than the Holley 735-cfm carb of the original engine, especially at higher rpm, where this engine was designed to perform.
20 Jon Kaase also supplied...
20 Jon Kaase also supplied the aluminum intake manifold for this project, which is a modern-style “spider” design. Its use, along with a velocity-enhancing 1-inch carb spacer means an even taller hoodscoop than the original is required when trying to close a Mustang’s hood over this monster.
21 Finally, an electronically...
21 Finally, an electronically controlled MSD distributor replaces the mechanical, vacuum-advance unit of the original engine. It delivers greater all-around performance and helps the engine maximize efficiency.
22 Here’s the fully assembled...
22 Here’s the fully assembled “new” Boss 429. It’s taller than the original and wears a few unique parts, but it is essentially an updated version with very similar assembly specs. (The electric water pump seen in the photo was used for dyno testing.) Though this engine produced 670 hp at 6,400 rpm and 556 lb-ft of torque at 5,600 rpm, the builders’ gripe was they simply weren’t able to exploit the engine’s full potential. A roller cam and an extra 100 cubes would push this engine past the 800hp mark, all within a relatively stock-looking package and good driveability traits for a street engine.