Navarro authored many articles in Hop Up, and later did the same in Hot Rod, always focusing on why things worked the way they did. In a story he wrote in March 1952, titled "How Many Pots?," he wrote: "If one more helps, a lot should do wonders," Navarro says. "This is the line of reasoning that is often applied to carburetion. After installing a basket of carburetors, the budding mechanic expects his car to leap like a jackrabbit when he punches the throttle. However, such a procedure often causes bitter disappointment rather than the fabulous performance that's expected. In fact, it is actually possible (and went on to explain why) to add so much carburetion to an engine that the car will slow down if the engine is floored under 35 mph in top gear..."

Soon several manufacturers, in addition to Navarro, offered three-carb intakes. Sharp's finned dual evolved into the snappy-looking "Triplet." Vic Edelbrock lost no time in marketing a competitive triple intake. Weiand, Offenhauser, Cyclone (who'd never made a dual), Evans, Fenton, and Edmunds followed suit. Andy Granatelli's dual manifold was an unabashed copy of the Edelbrock "Super", but his unique Grancor triple was never imitated. The center carburetor setup accommodated a four-bolt Rochester; the two end units were set up for three-bolt Stromberg 97s, permitting one large single carburetor for street use, and two flanking carbs for high-speed work.

A rare four-pot Schnell intake from the Pacific Northwest may have been the first commercial inline-four carb setup for a Flathead, when it appeared after Miller's Indy efforts, but very few were made. Californian Frank Baron was the first to sell a four-carb Flathead manifold, in volume, marketed under the Tattersfield brand. Before long, the leading speed equipment marketers of the era, like Edelbrock, Sharp, Fenton, Granatelli and Edmunds, all offered four-carburetor units. A few, now really rare four-carb manifolds were briefly sold by E&S, L&S, Lightning, Weiand, and Earl "Pappy" Evans.

By the mid '50s, as the Flathead's popularity began to fade, Navarro offered a four-barrel "Duo-Duplex" manifold for the '49-53 Ford and Mercury V-8s that used a then-contemporary '55 Thunderbird Holley Quadrajet carburetor and an oil bath air cleaner from an F-8 Ford truck. He claimed this setup, which he admired when Ray Crawford refined it for the winning Mexican road-race Lincolns, gave a 15-bhp increase, using the stock distributor. Soon afterward, Fenton, Offenhauser, Edmunds, Edelbrock, Sharp, and others sold four-barrel manifolds for the Flathead, principally to fit the '49-53 models.

Flathead devotees could order centrifugal superchargers from McCulloch and Italian-made Roots-type blowers from Italmecanicca, later S.Co.T (Supercharger Company of Turin (Torino)). I run one of these (with Eddie Meyer heads) on my '32 roadster. Perhaps a dozen Stephens-Frenzel centrifugal superchargers and special manifolds were sold. Good luck finding one. A few stalwarts adapted GMC 3-71s and 4-71s using S.Co.T, Navarro, or homemade manifolds. Those intakes (and the blowers) are highly collectable.

Navarro also offered a McCulloch supercharger kit to further enhance the four-barrel, and claimed a 5-psi boost was easily achievable. Unfortunately for the Flatheaders, Ford went to overhead valves in 1954, and Chevrolet followed in 1955 with a superior V-8 that quickly became a hot rodder's delight. By 1957, demand for Navarro's Flathead equipment had slackened. Successful survivors, like Edelbrock, Weiand, Offenhauser, and for a time, Edmunds, began casting intakes for the new overheads.