What is a 350 4 Bolt Main Block Worth?

Published by Dustin Babich on

The value of a 350 4-bolt main block can vary widely based on several factors including its condition, whether it’s been used or is new (if new blocks are still available), any additional machining or enhancements it has undergone, and its rarity or desirability among enthusiasts and builders. Generally, the 350 4-bolt main is a popular choice among those building or repairing Chevrolet small-block engines due to its perceived strength and durability, especially for performance applications.

Here’s a rough price range to give you an idea:

  • Bare block, needing work: $100 – $300
  • Machined block, good condition: $300 – $600+
  • Highly desirable casting number or “high nickel” block: Could potentially fetch a higher premium.

Overview of the 350 4-Bolt Main Block

The 350 4-bolt main block is a variant of the Chevrolet small-block engine, which has been one of the most popular and widely used engines in automotive history. The 4-bolt main refers to the four bolts securing the main bearing caps to the engine block, as opposed to two in the more common design. This is often preferred for high-performance applications because it provides additional strength to the bottom end of the engine, allowing it to handle more power and torque.

Factors Influencing Value


  • Used Condition: A used 350 4-bolt main block’s value depends on its wear and tear, any damage, and how much work it may need to be serviceable again.
  • Rebuilt or Remanufactured: Blocks that have been professionally rebuilt or remanufactured, especially with upgrades or enhancements, can be worth more.
  • NOS (New Old Stock) or New: On the rare occasion that a new or NOS 350 4-bolt main block is available, it would command a premium price.
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Enhancements and Machining

Blocks that have undergone machining processes such as boring to increase displacement, decking for a flat surface, or align honing for better main bearing fit can be more valuable, especially if done by reputable shops.

Rarity and Desirability

Certain casting numbers or production years may be more sought after due to perceived strength, making those specific blocks more valuable.

Market Demand

The local and global market demand can greatly affect the price. High demand in a region with a strong culture of muscle cars and hot-rodding can drive prices up.

Estimated Value Range

Given these factors, the value of a 350 4-bolt main block can range significantly. As a rough estimate, prices can start from a few hundred dollars for a used block needing work, to several thousand dollars for a block that is in excellent condition, has desirable casting numbers, or has been professionally machined and prepared for high-performance builds.


To determine the exact worth of a specific 350 4-bolt main block, one would need to consider its current state, history, and any additional work done to it. It’s also beneficial to compare similar listings and sales in the market, and possibly consult with professionals or enthusiasts within the automotive community.


How can I tell if a 350 block is a 4-bolt main?

You can usually identify a 4-bolt main block by removing the oil pan and inspecting the main bearing caps. A 4-bolt main will have four bolts securing each main cap, whereas a 2-bolt main will have only two.

Does a 4-bolt main always mean better performance?

While a 4-bolt main block is generally considered stronger and more capable of handling increased power and torque, the overall performance also depends on other factors such as the condition of the block, the build quality, and other engine components.

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Are all 350 4-bolt main blocks the same?

No, there can be variations in casting numbers, year of production, and original application that can affect their desirability and value. Some may also have undergone different levels of machining or modification.

Can I convert a 2-bolt main block to a 4-bolt main?

Yes, it’s possible to convert a 2-bolt main block to a 4-bolt main through a process called splaying, where additional bolts are added at an angle for increased strength. This process should be done by a skilled machinist familiar with performance engine builds.

Dustin Babich
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Dustin Babich

Dustin Babich

As the passionate author behind Automotivesimple.com, Dustin Babich is a knowledgeable expert in all things automotive. With a deep understanding of car tools, equipment, engines, and troubleshooting techniques, Dustin Babich shares invaluable insights, practical tips, and effective solutions to empower readers in overcoming car-related challenges.

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