A 4-Main Bolt Vs. a 2-Main Bolt Chevy Engine


The Chevy 350 crate engine comes in two styles: two-main bolt and four-main bolt. These engines are used by hot rod and sports car enthusiasts as replacements for existing engines that have less horsepower.

Four-Main Bolt

  • A four-main bolt engine has four bolts that connect the bearing caps to the engine block. This configuration allows for greater horsepower because the additional bolts add stability to the motor. A four-main bolt engine can maintain higher speeds for a longer duration of time.

Two-Main Bolt

  • Similar to the four-main bolt engine, on the two-main bolt model the bearing caps are secured to the engine block with two bolts. This engine has a lower horsepower than a four-main bolt engine but it tends to be reliable and is easy to repair.


  • The Chevy 350 four-main bolt engine offers 600 horsepower, while the two-main bolt engine can only generate 450 horsepower maximum. The torque on a two-main bolt motor is 65 foot-pounds; on a four-main bolt engine, torque is 80 foot-pounds.

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