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View Full Version : super charger and jackshaft ?



hmeric7
10-26-2010, 11:47 PM
i was looking itno some pullies for the jack shaft and supercharger. i see theres like 5% and ten % for both but have no idea how this work. i understand the faster the supercharger spins the more airflow but i was wondeirng how much you can go on stock fuel pump and injectors. also ihave a stock hb and pulley and i was wondering if i take them to a machine shop if theyll be able to check and c if they can zero balance them out. also with the super charge or jackshaft pulleys should you install underdrive pulleys on water pump alternator and crank?. jw guys thanx

96SCbird
10-27-2010, 02:03 AM
Overdrive and underdrive pulleys are two different things. An underdrive pulley will be a crank pulley with a larger pulley diameter for the accessories only. This will cause them to spin slower. An overdrive pulley could apply to the crank pulley, the jackshaft pulley, or the blower pulley. In any case, the pulley diameter is smaller so that it will cause the next component in the belt chain to spin faster. It is compounded as well, meaning if you have a 10% blower pulley and a 5% jackshaft pulley, you will effectively have 15% total overdrive on the blower. On an early SC, I think 5% is the most you can do without needing bigger injectors, but don't quote me on that.

Any competent machine shop will be able to check the balancer. Make sure there are no balance pins installed though. They should be zero balanced without any pins.

rzimmerl
10-27-2010, 07:39 AM
An underdrive pulley will be a crank pulley with a larger pulley diameter for the accessories only. This will cause them to spin slower. An overdrive pulley could apply to the crank pulley, the jackshaft pulley, or the blower pulley. In any case, the pulley diameter is smaller so that it will cause the next component in the belt chain to spin faster.

All of this is incorrect. The underdrive Crank pulley is smaller allowing the accesories to be slowed, an overdrive crank pulley is larger on the supercharger side. The same applies to an overdrive jackshaft, the crank side remains the same while the supercharger side gets larger overdriving the supercharger. An overdrive supercharger pulley is smaller then the stock diameter.