What is the difference between 225 and 198 Slant 6?
These two versions of Chrysler’s famed Slant-6 are the same family but differ mainly in how much air and fuel they can burn: the 225 cubic inch variant is larger and more torquey, while the 198 cubic inch version is smaller and generally more economical. Both share the distinctive slanted 6-cylinder layout that earned the lineage a reputation for durability.
How the two engines differ at a glance
Below is a concise inventory of the core distinctions between the 225 and 198 Slant-6 engines. The numbers reflect typical factory specifications across several generations; exact figures vary by year, carburetion or fuel-injection setup, and emission controls.
- Displacement: 225 cubic inches (about 3.68 liters) vs 198 cubic inches (about 3.25 liters).
- Power and torque potential: the 225 generally produces more torque and higher peak power than the 198, especially in model years when emissions equipment is not overly restrictive. Horsepower numbers vary by year and setup, with the 198 typically lower than the 225.
- Size and weight implications: the 225 is the larger, heavier variant, built for more demanding applications; the 198 is lighter and often preferred for small- to mid-size cars. This affects engine bay fitment and vehicle dynamics.
- Fuel and emissions systems: both began with carburetors in early years; later applications in some markets introduced fuel injection or advanced fuel-management features. The exact configuration depends on year and region.
- Application focus: the 225 found favor in larger cars, vans, and trucks where torque was desirable; the 198 found use in smaller cars and light-duty applications where efficiency mattered more.
In short, the displacement difference drives most of the practical gaps: more displacement generally means more torque and capability, at the cost of fuel economy and sometimes packaging constraints.
Design and engineering context
The Slant-6 lineage is defined by a 30-degree slant of the six cylinders, a design choice intended to give a compact, low hood line and straightforward maintenance. Across generations, Chrysler refined the block and head geometry, but the fundamental layout remained constant. The 198 and 225 variants share the same basic architecture, with changes concentrated in bore and stroke to achieve their respective displacements and related performance characteristics.
Shared traits of the Slant-6 family
Both engines benefited from the robust, long-stroke nature of the Slant-6, which emphasizes usable low-end torque. They also share common service considerations, such as durable cast-iron construction, a reputation for reliability, and a parts ecosystem that has kept restoration and maintenance options readily available for decades.
Parts compatibility varies by generation, but many gaskets, seals, and external fittings were designed to be interchangeable across broad swaths of the Slant-6 family. Always consult a specific year/model manual when planning a swap or rebuild to avoid fitment issues.
Performance and practical considerations
Owners and restorers weigh a few pragmatic factors when comparing the two engines. The following summarizes how the 225 and 198 typically differ in everyday driving, maintenance, and project decisions.
- Torque and driveability: the 225’s larger displacement usually yields stronger low- and mid-range torque, helpful for heavier loads or highway merging. The 198, while peppy in lighter applications, generally won’t deliver the same torque punch.
- Fuel economy: the smaller 198 generally delivers better highway fuel economy in similar vehicle types, though real-world results depend on gearing, condition, and drivetrain efficiency.
- Maintenance profile: both engines are known for durability, but maintenance habits (oil changes, cooling-system upkeep, and timing components) influence longevity in similar ways. Slant-6 engines, in general, benefit from clean cooling passages and regular valve-train inspection.
- Repair and parts availability: parts for both variants remain widely available through classic-car suppliers, with many components shared across the Slant-6 family. Specific items (such as certain pistons, cams, or cylinder heads) can differ by displacement, so verify compatibility before ordering.
- Swaps and replacements: for enthusiasts, swapping between 198 and 225 is possible in some applications but requires careful attention to engine mounts, exhaust, intake routing, cooling system routing, and accessory drives. Professional guidance and precise year-model matching are advisable.
For most owners, the choice between a 225 and an 198 comes down to vehicle type and intended use: heavier-duty applications lean toward the 225, while lighter, efficiency-focused builds can benefit from the 198.
Which one should you choose?
In planning a restoration, rebuild, or swap, consider these practical guidelines to decide which Slant-6 fits your project goals and chassis:
- Vehicle weight and用途: choose the 225 for trucks, full-size sedans, or vans where torque matters; select the 198 for lighter cars where simplicity and economy are valued.
- Intended use: if you anticipate carrying cargo or towing, the 225’s torque edge is advantageous; for daily commuting, the 198 can offer adequate performance with potentially lower fuel use.
- Occupation of space and fitment: verify engine bay clearance, exhaust routing, and mounting points, since the 225’s larger dimensions can affect fitment in tight spaces.
- Parts and support: confirm availability for your year and region; both engines enjoy strong aftermarket and scrapyard support, but some variants have more compatibility than others.
Choosing between the 225 and 198 Slant-6 is a matter of balancing torque, weight, economy, and fitment in your specific vehicle. Both engines remain durable options for classic Chrysler, Dodge, and Plymouth applications.
Summary
The 225 and 198 Slant-6 engines are siblings in Chrysler’s enduring inline-6 family. Displacement is the core differentiator, with the 225 offering more torque and capability at the cost of weight and, typically, fuel consumption, while the 198 provides lighter duty, better potential efficiency, and easier fitting in smaller cars. Both share the distinctive Slant-6 architecture, a long history of reliability, and a broad parts ecosystem that keeps these engines in circulation for enthusiasts and restorers alike.
How much can you bore a 225 Slant Six?
It is possible to bore a Slant 6 as much as 0.100" over, making the piston size 3.50", which increases a 225 to 238 cubic inches. Another size range to look at is the 87.5 to 89mm metric offerings (3.445 to 3.504).
What's the lifespan of a Slant 6 engine?
Chrysler's Famous Lopsided Engine Became A Legend With A 40-Year Lifespan.
What vehicles had the 225 Slant Six?
The 225 Slant Six found its way into everything from Dodge D-series trucks, Plymouth Valiants, and Dodge Darts, to fleet vehicles and industrial equipment.
How much horsepower does a 225 slant 6 have?
around 145 hp
The 225 was originally designed and introduced in 1960 for use in full-size models, and it eventually became the best known of the Slant Six engines. The original Chrysler 225 Slant Six produced around 145 hp (108 kW) at 4,000 rpm and 215 lb⋅ft (292 N⋅m) of torque at 2,800 rpm.
