Join Date: Nov 2001
Location: North Central Illinois
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Re: Underdrive Pulley?
Ok, I'll give it a shot, Crow. Underdrive pulleys do just that, in effect they "gear down" the engine accessories. This results in less drag on the motor, and frees up a few hp. Unfortunately, they do have some drawbacks. Your alternator won't be able to generate many amps since it will turn slower, mostly noticeable at idle, and engines sometimes have a problem with running hot at low speed since the water pump isn't turning fast enough. Philip's pulley is designed as 18% underdrive, not really enough to hurt a Zuk's accessories. Adjustable cam sprockets will allow you to tune the cam according to the engine. No two engines are alike, two identical ones will always run different. Once you start modifying a motor, many things change beyond what you have done. If you mill the head, you change the effective ratio of the timing belt, and changing cams will also effect valve timing. Sometimes, you get lucky, and everything works together, most of the time, it don't. Rocker ratios are nothing more than forcing the valve train to read the cam as bigger, longer duration and such. Stock rocker arm ratios on Zuks is 1.6, by increasing this geometry, you increase the lift and duration. On some cams, it helps quite a bit, on other cams it will actually hurt. Using modified rockers takes a lot of caution, as an aftermarket cam that is designed to maximize valve lift can cause the valves and pistons to hit each other, destoying a lot of money in the process. It's like Philip said, every little bit helps.
If it aint broke , I can still fix it...