Originally posted by 76chev
hey i have a question this guy i work with keeps bragging cuz he has a 350 four bolt main i was wondering what the difference is between my overbored 350 and his 4 bolt main??
4-bolt/2-bolt has to do with the number of bolts used to secure the main bearing caps to the block. Most standard production blocks used 2-bolt caps because they are cheaper to manufacture and are adequate to hold the bottom end of the motor together. 4-bolt caps/blocks were used where more severe use was anticipated, such as heavy duty trucks or where higher horsepower/rpm levels were planned. The caps have nothing to do with whether the block is overbored for larger pistons or not.