Mopar 360 Long Block: Dyno Test Breakdown and Performance Tuning Results

The Mopar 360 long block has long been a cornerstone of American V8 performance, offering an ideal platform for enthusiasts who want more displacement than the 318 but a more manageable package than a 440. Recently, a carefully controlled dyno test put a Mopar 360 long block through its paces with strategic performance tuning, and the results turned heads. The engine achieved a clean 360 horsepower at 5,500 RPM and 400 lb-ft of torque at 4,000 RPM. These figures represent a well-balanced powerband that delivers strong low-end grunt and respectable top-end pull. This article breaks down exactly how those numbers were achieved, what components were used, and what lessons can be applied to your own build.

What Makes the Mopar 360 Long Block a Strong Foundation

The Mopar 360 cubic inch V8, part of Chrysler's LA engine family, has been produced in various forms since the late 1960s. It strikes a sweet spot between bore and stroke dimensions, offering 4.00-inch bore and 3.58-inch stroke in its standard configuration. For this dyno test, the engine was sourced as a Mopar Performance long block, meaning it came with the block, rotating assembly, camshaft, timing set, oil pump, and cylinder heads already assembled. This approach saves time and ensures proper clearances from the factory.

The long block used in this test featured a cast-iron block with four-bolt main bearing caps for increased bottom-end strength. The cylinder heads were aluminum castings with 2.02-inch intake valves and 1.60-inch exhaust valves. Compression ratio was measured at 9.5:1, which is pump-gas friendly while still supporting meaningful power gains. The factory hydraulic flat-tappet camshaft was swapped out early in the process for a performance grind, a decision that proved critical to the final horsepower number.

Key Specifications of the Test Engine

  • Displacement: 360 cubic inches (5.9 liters)
  • Bore x Stroke: 4.00 inches x 3.58 inches
  • Block Material: Cast iron with four-bolt main caps
  • Head Material: Aluminum with 2.02/1.60 valves
  • Compression Ratio: 9.5:1
  • Camshaft: Custom performance hydraulic roller (224/230 duration at 0.050, 0.525/0.540 lift)
  • Induction: Single-plane intake manifold with 750 CFM carburetor
  • Ignition: MSD digital distributor and 6AL box

The Dyno Test Setup: Equipment and Methodology

To ensure accurate and repeatable results, the dyno test was conducted on a SuperFlow SF-902 engine dynamometer, which measures torque directly via a water brake absorber. The engine was run without accessories such as alternator, power steering pump, or fan, which is standard practice for engine dyno testing. Corrected horsepower and torque figures were calculated using SAE J1349 correction factors to account for temperature, barometric pressure, and humidity.

All test runs were performed with the engine fully broken in. The break-in procedure consisted of 20 minutes at varying RPM between 2,000 and 3,500 under no load, followed by three pulls to verify consistency before any tuning changes were made. Data was recorded at 100 RPM increments from 2,500 to 6,000 RPM. The test cell was maintained at 72 degrees Fahrenheit with 29.92 inHg barometric pressure for baseline runs.

Component List for the Test Build

  • Mopar 360 long block with aluminum heads and performance rotating assembly
  • Edelbrock Performer RPM intake manifold (single-plane design for top-end flow)
  • Holley 750 CFM mechanical secondary carburetor with vacuum secondary option for street manners
  • Hooker Super Competition headers (1.75-inch primary tubes, 3-inch collector)
  • Custom 3-inch mandrel-bent exhaust system with X-pipe crossover and flow-through mufflers
  • MSD Pro-Billet distributor with programmable timing curve
  • Mopar Performance valve covers with integrated breathers
  • Royal Purple 10W-30 break-in oil with high zinc content for flat-tappet protection

Performance Tuning: The Path to 360 Horsepower

Achieving 360 horsepower from a 360 cubic inch engine is no accident. It requires careful attention to air-fuel ratio, ignition timing, and mechanical components working in harmony. The tuning process for this build was methodical and data-driven. Let's walk through the key adjustments that made the difference.

Carburetor Tuning and Air-Fuel Ratio Optimization

The Holley 750 CFM carburetor was initially set with stock jets and metering rods. Baseline pulls revealed an air-fuel ratio of 12.8:1 at wide-open throttle, which is slightly lean for maximum power. By stepping up the primary jets from 68 to 72 and the secondary jets from 78 to 82, the AFR settled at 11.8:1, where the engine showed a measurable gain of 12 horsepower. The power valve was also changed from a 6.5 to an 8.5 to improve fuel enrichment under heavy load. Fuel pressure was maintained at 6.5 psi using a regulated electric pump.

Ignition Timing Adjustments

Ignition timing is one of the most influential parameters on an engine dynamometer. The baseline curve featured 15 degrees initial timing with 34 degrees total advance all in by 3,000 RPM. Through a series of incremental changes, the optimal curve was found at 18 degrees initial timing with 36 degrees total advance, arriving at 2,800 RPM. This change alone added 8 horsepower and improved throttle response significantly. The MSD box allowed for a programmable rev limiter set at 6,200 RPM to protect the rotating assembly during testing.

Spark Plug and Cylinder Head Considerations

Spark plug heat range was another variable that affected power output. Standard NGK FR5 plugs were replaced with one heat range colder FR6 plugs to prevent pre-ignition at higher RPM. Gap was set at 0.040 inch with the MSD ignition. The aluminum cylinder heads featured 180cc intake runners and 72cc combustion chambers. While these heads flowed well out of the box, a mild port match to the intake manifold gasket yielded an additional 5 horsepower at peak.

Exhaust System Influence

The Hooker Super Competition headers with 1.75-inch primary tubes were chosen for this build because they support mid-range torque without sacrificing top-end flow. The X-pipe crossover in the exhaust system helped equalize pressure pulses, improving scavenging. On the dyno, switching from a 2.5-inch collector to a 3-inch collector gained 6 horsepower at 5,200 RPM. The final exhaust setup included 3-inch mandrel-bent tubing with Flowmaster 40-series mufflers, providing a deep tone and low backpressure.

Dyno Results: Full Power and Torque Curves

The final pull on the dynamometer produced the following verified numbers:

  • Peak Horsepower: 360 hp at 5,500 RPM
  • Peak Torque: 400 lb-ft at 4,000 RPM
  • Horsepower at 3,000 RPM: 215 hp
  • Torque at 3,000 RPM: 375 lb-ft
  • Horsepower at 5,800 RPM: 342 hp (still pulling)
  • Torque at 5,800 RPM: 310 lb-ft
  • Maximum Power Band (90% of peak): 3,800 to 5,700 RPM

The torque curve was notably flat and broad, a characteristic of the 360 cubic inch displacement combined with the hydraulic roller camshaft. From 3,500 to 5,000 RPM, torque never dropped below 380 lb-ft, which makes this engine a strong candidate for street-driven vehicles, trucks, and lighter muscle cars.

Comparison to Other Mopar Engine Options

How does this 360 horsepower figure compare to other popular Mopar engines? The factory Magnum 360 from the mid-1990s produced approximately 245 horsepower in stock form. The 340 small-block from the late 1960s made around 275 horsepower with a four-barrel carburetor. Even the legendary 426 Hemi in its street configuration was rated at 425 horsepower, but with a much larger displacement and significantly more weight. This test shows that a properly tuned 360 long block can approach the power levels of much larger engines while maintaining a compact footprint and reasonable weight.

Practical Considerations for Building a Mopar 360

If you are considering a Mopar 360 long block for your own project, several factors beyond the dyno numbers deserve attention.

Drivetrain Compatibility

The 360 produces 400 lb-ft of torque at 4,000 RPM, which is enough to challenge most stock transmissions and differentials. A 727 TorqueFlite automatic or an A833 four-speed manual are common pairings. Consider upgrading the torque converter to a 2,500 to 3,000 RPM stall speed to maximize the powerband. The rear axle should be at least an 8.75-inch Mopar unit with 3.23 or 3.55 gears for street use. For track applications, 4.10 gears may be more appropriate.

Ignition System Upgrades

While the stock Mopar electronic ignition is reliable, a performance ignition system like the MSD setup used in this test provides better spark energy and timing control. The programmable timing curve allows you to dial in advance for different fuel grades and driving conditions. For more information on ignition tuning principles, check out this MotorTrend guide on ignition timing basics.

Cooling and Oil Systems

Aluminum heads reduce overall weight but still generate substantial heat under load. A high-flow water pump with a 180-degree thermostat and an aluminum radiator with electric fans is recommended. Oil capacity should be at least 5 quarts with a high-volume oil pump. A windage tray in the oil pan helps prevent oil starvation during hard acceleration and cornering.

Future Upgrades and Potential

The 360 cubic inch platform has substantial headroom beyond 360 horsepower. With a more aggressive camshaft, ported cylinder heads, and a compression ratio bump to 10.5:1, 400 to 420 horsepower is achievable on pump gas. Adding a supercharger or nitrous oxide system can push output well beyond 500 horsepower, though internal upgrades such as forged pistons and connecting rods become necessary. For a detailed discussion on small-block Mopar power potential, read this Hot Rod magazine Mopar 360 build guide.

Connecting with the Mopar Community

The Mopar performance community is one of the most active and knowledgeable in the automotive world. Engaging with other builders and enthusiasts can accelerate your learning curve and help avoid costly mistakes. Here are some resources worth exploring:

  • For A Bodies Only (forabodiesonly.com) — A dedicated forum for A-body Mopars with extensive engine build threads
  • Moparts (board.moparts.org) — One of the longest-running Mopar discussion boards with technical sections
  • Mopar Performance Parts Catalog — Official source for Mopar-specific components and technical specifications
  • YouTube channels such as Tom's Turbo Garage and Engine Power for dyno testing videos and build demonstrations
  • Local Mopar car clubs — Check the Mopar Club of America directory for events near you

Online Forums and Technical Resources

For those who want to dive deeper into the 360's tuning nuances, the For B Bodies Only forum has an active engine tuning section where builders share dyno sheets and carburetor calibrations. Another excellent technical resource is the Mymopar technical library, which hosts original factory service manuals, part numbers, and tuning specifications for the 360 and other Mopar engines.

Final Verdict: Is the Mopar 360 Long Block Right for You?

The results of this dyno test confirm what many Mopar enthusiasts have known for decades: the 360 cubic inch small-block is a versatile, durable, and tunable engine platform. Reaching 360 horsepower and 400 lb-ft of torque with a long block and thoughtful tuning is not only achievable but also repeatable with the right combination of parts. The powerband is broad enough for daily driving, while the peak numbers satisfy most performance goals short of all-out competition.

For anyone building a street car, weekend cruiser, or bracket racer, the Mopar 360 long block deserves serious consideration. It offers the classic small-block feel with modern component choices, and the aftermarket support is extensive. Whether you are starting from a bare block or purchasing a complete long block assembly, the path to 360 horsepower is well documented and proven.