How much horsepower does a 1966 327 have?
In 1966, the 327 cubic-inch V8 did not have a single fixed horsepower rating. Depending on carburetion and configuration, factory outputs ranged roughly from 250 to 300 horsepower. The top end came with the Tri-Power setup, while the 350-horsepower variant would not appear until the following model year in some high-performance Chevrolets.
Overview of 1966 327 Variants
The 327 was offered in several carburation configurations in 1966. The figures below reflect the factory gross horsepower ratings used at the time (note that these are not the modern net horsepower numbers).
- Two-barrel/base 327: around 250 horsepower
- Four-barrel 327: around 275 horsepower
- Tri-Power 327 (three two-barrel carbs): around 300 horsepower
In practice, the exact horsepower of a given 1966 327 could vary with exhaust, intake, and production tolerances. These figures capture the typical factory outputs Chevrolet advertised that year.
Historical Context and Model Variations
Chevrolet’s high-performance options for the 327 continued to evolve. While 1966 saw a range up to about 300 horsepower in the top configurations, the more extreme 350-horsepower 327 did not appear in 1966. That level would reappear later, notably in 1967 Corvette with the 327/350 horsepower option, as part of GM’s hot-rod era packaging.
Corvette and Other Applications
Corvette models equipped with the 327 saw the greatest emphasis on performance, including the Tri-Power and four-barrel variants. In 1967, the 327/350 horsepower option became a standout for enthusiasts, but in 1966 the common outputs remained within the 250–300 horsepower envelope.
How Horsepower Was Measured Then
During the 1960s, General Motors used gross horsepower ratings, measured with the engine tested in isolation and without the usual accessories. Modern comparisons use net horsepower, which accounts for accessories and emissions equipment. Therefore, a 1966 327 listed at, say, 275 horsepower gross may translate to a lower net figure on today’s measurements.
Summary
For a 1966 Chevrolet 327, horsepower depended on the specific configuration. Expect roughly 250 hp for base two-barrel engines, about 275 hp for four-barrel setups, and around 300 hp for Tri-Power configurations. The 350-horsepower 327 would not appear in 1966, with that higher output debuting in the following year’s high-performance Corvette and related models. When evaluating a classic 327, always verify the engine code and option package to confirm the exact ratings.
