I have a 99 civic si........ I just got done replacing my tranny. With the new tranny I also installed a act HD street/strip clutsh, Fidanza 7.5lb flywheel, Skunk2 short shifter and shift ****, Energy Suspension shifter stabalizer bushings, and a DC 4-1 ceramic header. Now it is time for tune up stuff (i.e. timing belt, serpentiene belt, plug wires, ect.) I have been looking at the unortodox underdrive pulley kit that comes with the lightened crank, alternator, ac, and one other pulley. Now I was wondering are these pulleys worth putting on my car. I figured that if im going to be in their anyway for the belts, I should do these also, but was wondering if it is a good investment. I havent really heard anything bad about them and that is why I ask your opinions. Any help you could give me would be great

 

this topic hs been debated quite a few times, this is what i understand from the numerous topics i have read, the alternator and power streering underdrive pullies are good.

now the controversy the crank pulley. most people will tell you they are ok to use and others will tell you because they do not have the rubber injected like the oem crank pulley ( the harmonic dampner) so instead of the crank pulley absorbing the vibrations the engine bearings will then absorb the vibrations cauing premature wear on them, hence shortening the engine life.

now i have not seen any results of this first hand but it sounds logical to me so im playing it safe and staying with a lightend balanced oem crank pulley

 

this is always a myth. people always say a brand new lighten crank pulley can have so much vibrations that could damage the crank/bearing. however, did anyone think about the other side of the crank? the flywheel and clutch. which one do you guys think will create more vibrations? an unbalance small light weight pulley? or a used/unbalance flywheel/clutch? i personally took many brand new flywheel and clutch to have them balance before i put them on. and most of them needed to drill something something to make it totally balance. so if someone tell me about how dangerous to put a brand new light weight pulley, then i think people might need to think about putting a new clutch(new pressure plate) without having them balance is also dangerous.