I have a 400 that I am putting in my 1978 F250 4x4. The stock crank pulley on the 400 has is fitted for 3 belts (usto have AC) but I only need 2 belts. So I have a 351M with a pulley that is only fitted for 2 belts (off of the 1978 F250). The only problem I have is that the 2 belt pulley has a weight and the 3 belt pulley doesnt. Is this weight on the pulley going to effect the ballance on my crankshaft?

 

Just switch the belt pullys. You don't have to change the harmonic balancer.

 

I didnt change the harmonic balancer. I need to change to pulley but the 2 belt pulley has a weight on it. Is the weight for ballancing the pulley or is it going to mess up the ballance on the crank?