Originally posted by erik erikson
What,if it has two bolt mains or 4- bolt mains has nothing to do with the size of the balancer.Be carefull,the 400 also has a 8 in. dia. balancer which is an external balance.The 400 balancer has an extra weight on the inside of the balance.You will also notice that some of the smaller dia. balancers are much thinner found on 283 and 327 small journal and the balancer used on a 305 is much thicker.
The extra weight is on the flexplate not on the dampener. The dampener has a machined groove/channel approx half of the circumference of the dampener. One other note, to my knowledge no 400sbc came with a standard transmission. To run a standard tranny behind a 400 sbc you will need a flywheel from a 454 bbc as they are also externally balanced.