I just got a set of underdrive pulleys. It say to but the underdrive pulley between the hub and the old pulley. To do this I think I'm going to need longer blots but if i pull them off to see what size they are i wont be able to go to the store to get any. So does anyone know the size bolt I will need to buy to save me some time and trouble?

 

the piggyback pulley didnt come with longer bolts?

 

I would just pull one of the bolts out and estimate the size, should only take a minute.

On thing I don't understand is why is it necesary to bolt the balancer back on. Assuming that the balancer is unweighted shouldn't it be fine to just run the underdrive pulley?

I allways thought one of the selling points of underdrive pulleys was that they weighed less, this actually adds weight.

 

Well I didn't buy it new. I bought it used from a guy on the fourm and he couldn't find the blots. And I don't understand why I put the stock pulley back on either thats just what it said do. Will it be ok not to put the old pulley back on?

 

It's realy a good modification? A guy is trying to sell me one for $30, but it's only the crank pulley with belt, i'm building a 396 with cam and heads, should i buy it?

 

i think you need the weight of the stock balancer to uhhh... balance the crankshaft. well, not really balance but to counterweight any imbalance in the shaft. in other words, to keep it from shaking.

 

Does anyone know the bolt size I will need to buy to put these pulleys on?

 

I was always under the impression the front of the crank was internally balanced, and the rear of the crank was externally balanced by the flexplate. If i am wrong somebody correct me please, but if i am right i dont see any reason on why you should need to bolt the orginal pulley back on. -Jeff