What is the difference between a 350 and 400 engine?
Two Chevrolet small-block engines, the 350 and the 400, differ mainly in displacement, bore and stroke, and the resulting torque and size. The 350 is about 350 cubic inches with a 4.00-inch bore and a 3.48-inch stroke, while the 400 is about 400 cubic inches with a 4.125-inch bore and a 3.75-inch stroke. This translates to more low-end torque in the 400, a heavier, less rev-happy package, and different internal components and mounting considerations.
The following sections break down the key distinctions, why they matter for builders and drivers, and what to consider when choosing between a 350 and a 400 for a project or restoration.
Key technical differences
Below are the core specifications and mechanical implications that enthusiasts typically compare when evaluating a 350 versus a 400 small-block engine.
- Displacement: 350 vs 400 cubic inches. The 400 is roughly 50 cubic inches larger, which translates to more torque potential at lower to mid-range RPMs.
- Bore size: 4.00 inches on the 350; 4.125 inches on the 400. The larger bore on the 400 allows more air and fuel intake per stroke but requires a block with the bigger cylinder diameter.
- Stroke: about 3.48 inches on the 350; about 3.75 inches on the 400. The longer stroke of the 400 increases displacement and affects the engine’s torque curve and rod/piston geometry.
- Block and internals: The 400 typically uses beefier main webs and sometimes different crank/rod/piston configurations to handle the increased displacement and stress. A 400-block is not simply a bored-out 350 block; it is a separate design with appropriate clearances and reinforcement in many cases.
- Performance characteristics: The 400 tends to produce stronger low-end torque, making it feel more responsive under acceleration at lower RPMs. A well-built 350 can excel at higher RPM power and can be stroked or boosted for a broader range of performance, depending on the build (heads, cam, induction, and exhaust).
- Availability and aftermarket support: The 350 is far more common, with a vast aftermarket ecosystem, a wide range of crate engines, and easier parts availability. The 400, while supported, is less common, which can affect pricing and lead times for parts, especially for block selection and internals.
- Fitment considerations: The 400’s larger bore and longer stroke can impact engine bay packaging, hood clearance, radiator capacity, and exhaust routing. In some classic cars, the 400 may require additional clearancing or custom mounting work.
In practice, these technical differences show up in daily driving and in how the engine responds to tuning, gearing, and weight. The 400’s torque makes it attractive for heavier cars, weekend-warrior builds, and trucks, while the 350 offers versatility for lighter cars, high-RPM street performance, and easier swap/maintenance paths.
Practical implications for builders and drivers
Before committing to a 350 or a 400, consider how you plan to use the vehicle, your budget, and how you’ll source parts. The choice will influence performance, reliability, and long-term maintenance.
- Performance goals: If your aim is strong off-the-line torque for a heavier car or a pickup, the 400 is appealing. If you want lively high-RPM response for a lighter street car, a well-built 350 (or a 383 stroker) can be a better fit.
- Budget and parts availability: The 350 is cheaper to build and restore due to abundant parts and crate options. The 400 can be more expensive due to less common blocks and internals, though crate-engine options exist.
- Fitment and engineering: Check hood clearance, radiator capacity, exhaust routing, and transmission/torque-converter compatibility. The 400’s larger displacement can require more cooling capacity and careful fitment planning.
- Reliability and maintenance: A properly built 350 is robust and easy to service with widely available parts. A 400 build demands attention to the bottom end and lubrication system to avoid undue wear in daily driving scenarios.
- Upgrade paths: Both engines respond to modern induction, cam, and head work, but the pathways differ. A popular route for enthusiasts is building a 383 stroker (350 block with a 400 crank) to combine 350-block charm with extra displacement and torque.
For most car enthusiasts, the choice hinges on the intended use: torque-rich performance in a heavier chassis or a lighter, rev-happy setup in a classic car. The right path balances your goals with budget, availability, and build complexity.
Common upgrade paths and swaps
Stroking a 350 to create a 383 stroker
One of the most popular upgrades is the 383 stroker, which uses a 400 crank in a 350 block (with suitable pistons and rods) to yield about 383 cubic inches. This approach delivers greater torque than a stock 350 while maintaining the smaller-block packaging. It requires careful attention to piston diameter, rod length, compression height, and oiling to ensure reliability, but aftermarket kits and guidance are widely available.
Using a 400 block for a bigger-performance build
Some builders opt for a true 400 block for a straightforward 400 or a stroked variant, especially when mounting into a chassis that can accommodate the space and cooling needs. This route emphasizes robust bottom-end support, appropriate cylinder bore clearance, and potential upgrades to the cooling and fuel systems to handle the increased displacement and torque.
In both scenarios, professional assembly and precise specifications (crank journal size, rod length, piston compression height, deck clearance, and head/gasket compatibility) are essential to ensure longevity and reliable performance.
Summary
The 350 and 400 are siblings in the Chevrolet small-block family, sharing many design principles but diverging in displacement, bore and stroke, and internal robustness. The 350 provides a lighter, more rev-happy platform with broad aftermarket support, while the 400 delivers stronger low-end torque and a heavier footprint, often with more demanding packaging requirements. Your choice should reflect the vehicle, desired driving character, and available budget, with an eye toward compatibility, cooling, and maintenance considerations. For many builders, a 383 stroker offer a practical compromise that blends the best of both worlds.
