Buyer's Guide for Pulleys: Round and Round She Goes

Underdrive pulleys — underrated upgrade

Underdrive Pulley
Keep your head in it and you'll gain big time
If you're a regular reader of mine (and if you aren't, you should be!), you know that I'm really big on engine efficiency. You know that the sound of a high-revving, free-breathing engine is like Jessica Simpson to my ears. Well, now that you've followed my insightful advice and replaced your stock intake and exhaust headers, it's time to take a look at some more bolt-on engine enhancers. This time, we'll take a look at a personal fave of mine: underdrive pulleys.

Yes, pulleys. A completely different type of spinner, they're the unsung heroes of the internal combustion world. Yeah, I know — pistons and valves get all the glory, but without pulleys, a lot of really important stuff wouldn't get done. The alternator, power steering pump, water pump, oil pump, cooling fan, and air conditioning compressor all rely on the humble underdrive pulley to do their work. Let's take a closer look at what actually goes down on the pulley end of the engine and learn how to make it more efficient.

SRD Pulley for Honda
Pulleys are real pretty
The underdrive pulley rides on the crankshaft and turns with it on piston power. A serpentine belt rides on a groove cut into the pulley, and that belt loops around smaller pulleys attached to the other engine components I just mentioned, forcing them to turn as the underdrive pulley turns. In essence, we've just added a whole lot of extra load on the crankshaft; not only does it have to turn the wheels, but it also has to recharge the battery, cool the engine, and so forth. And that IS a big load!

So, what can we do to lighten the crank's job? Replace the pulley, of course! Like most stock engine parts, the pulley is engineered to: a) cost as little as possible, and b) work reliably for 100,000 miles.
AEM Pulleys
... and AEM Pulleys are colorful
Performance is secondary to economy and reliability. For this reason, most pulleys are made of cast iron-just like Grandma's old cast iron skillet. Cast iron might have been cutting-edge technology back when Stonehenge was being built, but for a ride worthy of Kid Turbo's praise, a good, modern pulley should be made of lightweight aluminum.

Think of Grandma's skillet for a sec. It makes great fried chicken, but if you've ever tried to lift it, you know that it weighs a freakin' ton. I'll bet that if you cook fried chicken (Yup, you can actually make fried chicken yourself, without the involvement of anyone from Kentucky), you'd probably fry it in an aluminum skillet. It works just as well, but it weighs about one tenth of what Grandma's skillet weighs.

A performance pulley is milled from lightweight billet aluminum and weighs a fraction of what the stock pulley weighs. Less weight means less force is necessary to turn the pulley. Moreover, its width and groove pattern are designed to maximize efficiency without creating extra friction on the belt. A lightweight pulley will allow your engine to reach high RPMs sooner, helping your engine climb smoothly into its powerband. You can expect about 6 to 10 additional horsepower and 7 to 12 more foot-pounds of torque after installation. Still not convinced? Well, I've got one more reason to upgrade up my sleeve: aluminum pulleys look way cool! Most are shiny silver but some brands offer anodized pulleys to match whatever other under-the-hood bling you may have on your ride.

As for installing the bugger, it's pretty easy, but you'll need a good torque wrench and access to the bottom of your engine. PLEASE don't just jack up your car and slide under there-I want you to be alive to read my next article. If you don't have a set of reliable jack stands, I'd recommend having it installed by someone who does.

Now comes the fun part. I'd recommend pulleys from AEM and Unorthodox Racing. You can find underdrive crankshaft pulley kits from all these brands (and others) right here in the Andy's Auto Sport Store. If you need help choosing a pulley, just give the sales folks a call and tell them that you're ready to fry your chicken in an aluminum pan. They'll understand. Trust me.

Cliffnotes: Pulleys create horsepower at the wheels by lightening the load on the driveshaft, and are straightforward to install, relatively cheap, and make a noticeable difference.