GM Small Block 400ci Engine

A GM Small Block 400ci Engine refers to a GM Small Block 400ci Engine  that fits the  GM Small Block 400ci Engine architecture. Here’s an overview to help clarify what it is and what makes it desirable or unique:

General Overview

• Displacement: 400 cubic inches (6.6 liters)

• Configuration: V8

• Block Type: Small Block Chevy (SBC)

• Production Years (OEM): 1970–1980

• Original Use: Passenger cars and trucks (Chevrolet Monte Carlo, Impala, pickups, etc.)

Key Characteristics

Why It’s Popular

• Largest SBC Displacement: From the factory, it’s the biggest small-block Chevy ever made.

• Torque Monster: Thanks to its long stroke, the 400 SBC produces a lot of low-end torque.

• Stroker Builds: Often used as a base to build stroker engines like a 406, 421, or even 434 cubic inch engines.

• Aftermarket Support: Tons of performance parts are available due to SBC compatibility.

Things to Watch Out For

• Cooling Issues: Requires steam holes in cylinder heads to avoid hot spots.

• External Balance: Needs proper harmonic balancer and flexplate/flywheel matched to the 400.

• Block Thickness: Early GM Small Block Compatible 400 c.i. Engine  are often preferred due to thicker cylinder walls, better for performance builds.

Popular Applications

• Hot rods

• Street/strip cars

• Circle track racing

• Marine engines

• Off-road trucks

Aftermarket Options

If you’re not using an original GM Small Block 400ci Engine , many aftermarket blocks are:

• Made from stronger cast iron or aluminum

• Offer improved oiling, thicker cylinder walls

• Designed to handle over 600+ horsepower

• Available from Dart, World Products, BluePrint Engines, etc.

Would you like help sourcing a crate version or building one (e.g., a 406 stroke

Absolutely! Let’s continue with a deeper dive into GM Small Block 400ci Engine , crate engines, and performance upgrade paths.

Common 400 SBC Builds & Variants

Because the GM Small Block 400ci Engine  is a torque-heavy platform with a strong aftermarket, many enthusiasts go beyond stock specs. Here’s how:

Stroker Builds

These increase displacement by changing the crankshaft stroke and/or bore size.

Crate Engine Options (400 SBC & Variants)

Here are a few well-known builders that offer crate or turnkey engines based on the 400 SBC:

BluePrint Engines

• 406ci Stroker SBC

  • ~450–500 hp / 500+ lb-ft

  • Hydraulic roller cam

  • Dyno tested and backed by warranty

  • Compatible with pump gas

Dart / World Products

• Offer bare and assembled aftermarket GM Small Block 400ci Engine :

  • Dart SHP or Little M blocks are highly recommended for high-horsepower street or race builds.

ATK High-Performance

• Turnkey 406ci and 421ci engines

• Options range from street-friendly to track-only

• Dyno sheets included with purchase

Summit Racing / Jegs

• You can buy assembled long blocks, short blocks, or full turnkey engines

• Brands: BluePrint, ATK, Dart, Speedmaster

Common Performance Upgrades

Common Questions & Answers on GM Small Block 400ci Engine

Q: Can I use standard SBC heads on a 400?
 Yes, but you need to drill steam holes into the heads or buy heads with them pre-machined to avoid overheating.

Q: Is the 400 SBC internally or externally balanced?
Externally balanced—unlike the 350 or 327. You must use the correct balancer and flexplate.

Q: How much power can a 400 SBC handle?
 A stock block can usually take 500–550 hp with the right build. Aftermarket blocks can handle 700+ hp reliably.

Q: Is the 400 SBC still viable today vs. LS engines?
 Absolutely. While LS engines are more modern and efficient, a 400 SBC has tons of low-end torque, is easier to work on for many, and still dominates in classic and retro applications.

 Ideal Applications for a 400 SBC

• Classic Muscle Cars (Camaro, Chevelle, Nova)

• 4×4 and Off-Road Builds (K5 Blazer, C10, etc.)

• Drag Cars / Bracket Racing

• Restomods

• Marine / Boat Engines

• High-performance Street Rods