About two years ago I came acrross and article were it said that you can gain 15+ horse power on you car in you install an undrive pulley. I bougt an Unorthodox Racing Pulley for my 1996 Nissan 300zx but was not sucessful in installing it because I could not find the shorter belts anywawhere.

This week I attempted to install the pulley (after being in a box for 2 years) and this time it worked great. So if you are thinking about upgrading your pulley or wanting more horse power to your car by installain an underdrive pulley, here i will show you how i did mine.

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The most popular crank pulleys are the Unorthodox Racing Pulleys ( http://www.unorthodoxracing.com ), the ones I am familiar with. This version of their crank pulleys increases performance because they underdrive all the accessories (15-20% more power), unlike accessory only kits out there that do not include the crank pulley. This means one you air conditioning is on theircrank pulleys give you more power back to the wheels by not letting the air conditioning compressor rob as much power.
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However, they do not push the amount or percentage of underdrive too far for two main reasons. First, it is important to keep charging systems, air conditioning, power steering, and water pumps moving fast enough for every day driving. Second, not much horsepower is gained from extreme underdriving. they always keep theirunderdrive percentage under 20% which is what allows us to maintain factory specified outputs for all ytheiraccessories. theirtesting has found for most vehicle models you can upgrade their stereo to a system of up to 600 watts (RMS) and not have any charging problems.

For most applications all of the underdriving is done at the crank pulley, not the accessory pulleys. This is done so maximum weight loss can be achieved at the crank where most of the horsepower gains are realized. The Ultra Series underdrive crank pulleys are available in polished aluminum finish.


1. The first step is to shop for your pulley.

2. Once you are ready to install the new pulley, you will need to remove all the necessary engine accesories to gain access to the crankshaft pully or harmonic balancer (as is sometimes called). On my car, i had to remove the radiator and the clucth fan
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3. Next remove all the belts (power steering, alternator, Air Conditioning, etc)

4. Once you have cleared all the engine accessories, the next step is to remove the OEM pulley. To do this, you need muscle. To remove the old pulley, you have these options:

AIR POWER - If you have an air powered Impact Gun, this is the easiest way to remove it

ElECTRIC POWER - If you don't have air tools, you can buy cordless impact drills. I've never used one of these before, so i don't know if it has enought torque to remove the bolt holding the pulley.

HUMAN POWER - If you cant afford or don't have power tools, use your own muscle to remove the pulley. If you have to use your own muscles to loosen the pulley's bolt, you have to get a long breaker bar and a vise-grip with chains, like the ones in this picture. If you use the method, make sure to put a cloth towel in between the chain and the pulley to avoid damage to your pulley. (second picture with yellow arrows)
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MY METHOD - For me, the easiest way to loosen the bolt was to use an impact gun i bought at walmart to remove tires. Its a handy tool to have to easily remove tires from your cars. Its not the recommded way to do this, but it works for me since I can't affor air or power tools. If I didn't have this, i would have to use the HUMAN METHOD.
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5. Once you have the bolt loose, leave in at about 3/4 out and remove the pulley out with a pulley pull removal tool.
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6. With the old pulley removed, install the new under drive pulley.
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7. ONce you have the new pulley installed, do reverse to put everything you removed back together - DONE

I hope this has helped you.