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

by Amanda Hevener

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.

About the Author

Amanda Hevener has been a freelance writer and photographer since 2006. She is a member of the Akron Press Club. Her writing has appeared on SeededBuzz, Swords.com, Baseball Fandom and Deep Left Field. She reviews restaurants for AltOhio and other websites. She has a Bachelor of Arts in journalism and English from Ashland University.

Photo Credits

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