How much horsepower does a Mopar 400 have?
The Mopar 400 refers to Chrysler’s 400 cubic inch V8 used in various Mopar muscle cars and full-size models during the late 1960s and early 1970s. There isn’t a single, universal horsepower figure for this engine—the number depends on the exact year, carburetion, cam profile, compression ratio, and whether the factory rating is gross (older convention) or net (the later SAE standard). What you’ll typically see in period literature is a range rather than a fixed value.
What is the Mopar 400?
The Mopar 400 is part of Chrysler’s big-block V8 lineage and was employed in a variety of vehicles—from high-performance models to everyday heavy-duty applications—through the late 1960s and into the early 1970s. Like other Mopar big-blocks of the era, horsepower varied with configuration, emissions requirements, and the rating method used by the manufacturer.
Key factors that affect horsepower
Several elements determine the advertised or measured power output of a Mopar 400. The following list highlights the main influences you’ll encounter when comparing engines from different years or configurations.
- Carburetion and cam profile: Four-barrel carbs and performance camshafts typically produced the higher end of the range, while smaller carb setups or milder cams yielded lower numbers.
- Compression ratio and fuel: Higher compression generally increased horsepower, whereas lower compression used in later years to meet lower-octane fuel standards reduced power output.
- Rating method: Early years used gross horsepower (engine output without drivetrain losses), while later years shifted to SAE net horsepower (which accounts for accessories and exhaust), causing published numbers to look smaller.
- Emissions and exhaust equipment: Emissions controls and exhaust restrictions in the early 1970s reduced measurable power in many Mopar 400 builds.
In practice, the exact horsepower depends on the specific build and year, so two Mopar 400s from different periods can have noticeably different numbers even if they share the same displacement.
Typical stock horsepower ranges
Below are general ranges you might encounter when looking at factory specifications for the Mopar 400, differentiated by rating method and era. These are approximate values intended for context rather than precise catalog figures.
- Gross horsepower (factory rating used in the late 1960s for many 4-barrel, performance-oriented 400s): typically about 340–360 hp, with some high-performance configurations reaching into the low 360s.
- Net horsepower (SAE net, adopted in the early 1970s): commonly around 230–320 hp depending on configuration, exhaust, and cam/compression settings.
- Emissions-era adjustments (mid- to late-1970s): net ratings could be in the lower end of that range, often around 210–270 hp for more constrained setups.
Put simply, the Mopar 400’s horsepower is not a single figure; it spans a broad range across years, models, and rating standards. If you’re evaluating a specific engine, the exact build details matter greatly.
How to verify horsepower for a specific Mopar 400
To determine the horsepower of a particular Mopar 400, use a methodical approach that accounts for the engine’s identity and rating standard. The steps below outline a practical way to verify what you have or are considering.
- Locate the engine code and date code on the engine block or pad, which identifies the exact variant and production period.
- Check the car’s original build sheet, fender tag, or window sticker (where available) to confirm the factory rating method (gross vs net) and configuration for that engine.
- Reference factory specification charts or reputable Mopar resources (service manuals, dealer literature, or enthusiast databases) for the exact engine code and year to identify the official horsepower rating for that configuration.
- If you want a modern, practical measure, arrange a professional engine dyno test to determine actual horsepower and torque, recognizing that drivetrain losses will affect the crankshaft output versus what you read on a wheel dyno.
Following these steps will give you a reliable sense of the Mopar 400’s horsepower for a specific car or build, rather than relying on generic numbers in isolation.
Summary
The Mopar 400’s horsepower varies widely by year, configuration, and how the horsepower was rated (gross vs net). In the late 1960s, factory gross ratings commonly placed the 400 in the low-to-mid 300s hp, while SAE net ratings in the early 1970s typically fall in a broad range of roughly 230–320 hp. Emissions controls and rating-method changes in the mid- to late-1970s further reduced published numbers. For an exact figure, consult the engine’s code, the car’s build documents, and period specification charts—or have the engine dyno-tested for a modern reference.
How much horsepower does a 1972 Dodge Charger 400 have?
As muscle cars declined, the 1972 Dodge Charger Rallye kept the spirit alive. Replacing the Super Bee, the Rallye was Dodge's new performance trim. The most potent option was the 400 Magnum V8, producing 280 net horsepower with 4-barrel induction.
How much horsepower does a 1977 Dodge 400 have?
1977 Dodge Royal Monaco Brougham V-8 400 c.i. 190 h.p. automatic 3 speed.
How much horsepower does a Mopar 400 big block have?
With a relatively low 8.2:1 compression ratio, the final 400 V8 version produced a mere 195 horsepower and 305 lb-ft of torque. Earlier takes on the same design delivered more performance in a smaller package. If the engine had lost some sheer power, however, it had improved in quality.
How much horsepower does a 400 small block have?
A 400 small block's horsepower varies dramatically, from about 150–300 hp from the factory to over 1,000 hp in a highly modified, supercharged drag-racing application. For a mild street build, 350–500 hp is a realistic goal, while a performance build could easily reach 400–500 hp with better heads and a cam.
Stock vs. modified
- Factory: Stock engines from the 1970s typically produced between 150 and 300 horsepower, with the lower end coming from less-equipped models and the higher end from factory performance versions.
- Mild Street Build: A common goal for a street-friendly build is 350–500 horsepower. This can be achieved with upgrades like better cylinder heads, a more aggressive camshaft, and improved intake/exhaust systems.
- Performance/Racing Build: High-performance builds can make significantly more power.
- A well-built, naturally aspirated engine could approach 500–600 hp.
- For even higher power, engines with power adders like superchargers have reached over 1,000 horsepower.
Factors that influence horsepower
- Cylinder heads: Stock heads often restrict performance, and upgrading to better-flowing heads is one of the most effective ways to increase horsepower.
- Camshaft: The lift and duration of the camshaft are critical to power output.
- Compression ratio: A higher compression ratio generally increases horsepower, but requires higher-octane fuel.
- Fuel and air delivery: Upgrades to the carburetor, fuel injectors, and intake system can boost performance.
- Power adders: Superchargers and turbochargers can drastically increase horsepower, but often require a more robust and heavily modified engine.
