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How To Understand The Holley 4180
In 1983-'85, The 5.0L HO Mustangs Came With A Holley Four-Barrel That's Different Than The Typical Holley Performance Carburetor
If you were around for the detuned Mustangs in the 1970s, you can appreciate what it felt like when Ford brought back the Mustang GT in 1982. While it was a good-looking ride, it wasn't much on performance. In fact, it was more show than go with its 5.0L High Output V-8 with a 351W marine performance camshaft and, believe it or not, a Motorcraft 2150 two-barrel carburetor under the aluminum dual-snorkel air cleaner.
But for 1983, Ford stepped up the power to 175 hp, thanks primarily to a Holley 4180 four-barrel carburetor. Although 175 hp isn't a page-turner in these days of 700hp Shelby Super Snakes, it was a big deal in 1983 because it was a major improvement over '74-'82.
Holley carburetion atop a small-block Ford in 1983 was surreal considering the strict federal mandates of the era. The early 1980s was an era of vacuum hoses, check valves, smog pumps, exhaust gas recirculation devices, and stifling single catalytic converter exhaust systems. For Ford to actually fit the Mustang with a Holley carburetor was a big deal, mainly because of Holley's century-long ability to design and build great performance carburetors.
Waltz out to any racing event-be it drag racing, road racing, dirt track, marine, etc.-and you will primarily find Holley carburetors. One reason is because Holley performance carburetors are easy to tune and service. For the '83 Mustang 5.0, Holley engineers took on the challenge of designing a 4180 version with both emissions and crisp performance in mind.
What makes the Holley 4180 different from its aftermarket 4150/4160/1850 cousins is the tamper-proof metering block that makes it virtually impossible to adjust the idle air mixture. Also different are the primary boosters, which are annular discharge to reduce emissions. Conventional Holley primary metering blocks will not interchange onto the 4180. However, with minor modifications, secondary 4150 metering blocks will interchange to improve wide-open throttle performance. Center-pivot Holley fuel bowls will also interchange if you use Nitrophyl floats instead of the brass types. It is important to note that '83-'85 Mustangs probably won't pass a smog check with these bowls because doing so eliminates the evaporative emissions system, which, by the way, has no bearing on power output.