128601101 SPEEDMASTER Billet Iron Engine Block B-4 400 125

Review SPEEDMASTER Chevy Sbc 4-bolt Billet Main Bare Iron Engine Block for CHEVY B-4 400 125

The Speedmaster 128601101 Chevy 400 B-4.125 M-400 DH-9.025 4-bolt billet bare iron engine block is a high-performance component designed for use in racing and high-horsepower applications. This engine block is a billet iron design, meaning it is machined from a single piece of iron, ensuring superior strength and durability.

The Chevy 400 B-series engine block is a popular choice among hot rod and muscle car enthusiasts due to its large displacement and potential for high power output. This particular block, with a bore size of 4.125 inches and a stroke length of 3.75 inches, offers a total displacement of 400 cubic inches.

The 4-bolt main configuration of this engine block provides increased rigidity and improved oiling, allowing for higher engine speeds and increased power. The mains are drilled for 4-bolt main caps, and the block deck is flat to ensure proper sealing of the cylinder head gaskets.

The cylinder bores are finished to a mirror-like surface, ensuring a perfect seal with the piston rings and cylinder liners. The block also features a deep skirt design, which helps to support the pistons and increase the overall strength of the engine.

The crankshaft journal surface of this engine block is designed to accept a 4.000-inch crankshaft, and the block is also equipped with a doweled crankshaft locating surface. The block is also equipped with a standard oil pump boss and a front oiling system, allowing for proper oiling of the crankshaft and connecting rods.

The engine block is designed to be used as a bare block, meaning it does not come with any additional components such as cylinder heads, pistons, or connecting rods. This allows the user to customize the engine to their specific needs and performance goals.

In summary, the Speedmaster 128601101 Chevy 400 B-4.125 M-400 DH-9.025 4-bolt billet bare iron engine block is a high-performance component designed for use in racing and high-horsepower applications. With its billet iron design, large bore size, and 4-bolt main configuration, this engine block offers superior strength, increased rigidity, and the potential for high power output.

Pros and Cons of Buying a Chevy 400 B-Series Billet Iron Engine Block (Speedmaster 128601101)

The Chevy 400 B-Series billet iron engine block (Speedmaster 128601101) is a popular choice among automotive enthusiasts and professional racers due to its strength, durability, and high-performance capabilities. However, like any other engine component, it comes with its advantages and disadvantages. In this analysis, we will discuss the key pros and cons of buying this billet iron engine block.

1. Strength and Durability: The billet iron construction makes the engine block stronger and more resilient to high-performance applications and racing conditions.

2. Customizability: Since it is a bare block, you can customize it according to your specific engine build requirements, such as bore size, stroke length, and deck height.

3. Weight Reduction: Compared to the cast iron blocks, billet iron blocks are lighter, which can result in improved power-to-weight ratio and better overall performance.

4. Improved Heat Dissipation: The billet iron material allows for better heat dissipation, which can help maintain optimal engine temperatures and prevent thermal stress.

5. Better Engine Balance: The uniform material and structure of a billet iron block can lead to improved engine balance, resulting in smoother engine operation and reduced vibrations.

1. Cost: Billet iron engine blocks are generally more expensive than their cast iron counterparts due to the more time-consuming and labor-intensive manufacturing process.

2. Complexity: The bare block design requires additional work to assemble the engine, including machining the cylinder bores, installing the crankshaft, and other related components.

3. Limited Availability: Due to the niche market, billet iron engine blocks may not be as readily available as cast iron blocks, which could lead to longer waiting times for delivery or installation.

4. Higher Maintenance: Since the billet iron block is a bare component, it may require more frequent maintenance and upkeep to ensure optimal performance.

5. Potential for Warpage: The billet iron material can be prone to warpage during the manufacturing process if not properly controlled, which could result in potential engine issues.

The Chevy 400 B-Series billet iron engine block (Speedmaster 128601101) offers several advantages, such as increased strength, durability, customizability, weight reduction, and improved heat dissipation. However, it also comes with some disadvantages, including a higher cost, complexity, limited availability, higher maintenance requirements, and potential for warpage.

Based on the analysis, if you are seeking a high-performance engine block for racing applications or custom engine builds, the billet iron block could be a worthwhile investment. However, if you are looking for a more affordable and readily available option, a cast iron engine block may be a better choice for you. Ultimately, the decision depends on your specific engine build requirements, budget, and availability.

Details:

Specs brand: Speedmaster part number: 1-286-011-01 type: engines, bare block cylinder bore diameter: 4.125 in. Best of all can be used with standard off the shelf small block components. Bore quantity: sold individually. Precision pre-machining is the perfect starting point for a powerful and reliable engine eliminating time expense of blueprinting stock block or ''semi-finished'' factory casting.

Design from the ground up based upon your favourite Bowie block with ability to handle naturally aspirated, supercharged, turbocharged and notorious applications. Bore stroke: 4.185 in. Timing chain/gears: standard sbc components. Starter: standard sbc.

Overview if your standard Bowie block could handle 1500 hp it would be Speedmaster h1 engine. Max recommended cam journal od: standard sbc - 1.869 plug: 2.375 in. Oil pan: standard sbc. Timing cover: standard cam location sbc.

specifications engineblocksam:

• for models: B-4, 400, 125
• for makes: Chevy
• brand: Speedmaster
• mpn: 128601101
• type: Engine Block
• manufacturer warranty: 1 Year

seller engineblocksam:

• # reviews: 1539
• city: rialto, california
• rating: 99.1%

payments engineblocksam:

• wallet: paypal
• other
• credit card: diners-club

general engineblocksam:

• category: Auto Parts > Car Truck Accessories > Engines > Blocks

offer engineblocksam:

• sold #: 14
• started: november 5, 2025
• prices: $2167.58–$2596.65
• item condition: New
• in stock #: 3
• options: ship-to-home
• availability: in stock

returns engineblocksam:

• policy: returns accepted
• paid by: seller
• time: 30 days

shipping engineblocksam:

• service: flat rate freight
• type: fixed
• class: freight