Lower Gear = More Power

One of the easiest, most effective bolt-on items you can get is a set of underdrive pulleys for your engine. These cause the accessories (water pump, alternator, power-steering pump, and a/c compressor) to spin slower, diverting some extra power to the drivetrain. If you've ever ridden a 10-speed bike, the effect is like shifting into a lower gear -- the underdrive crankshaft pulley (analogous to the front sprocket on your bicycle -- it provides the turning power) is smaller than stock, and the accompanying water pump and alternator pulleys (the "rear sprockets") are larger. Of course, since the driven pulleys won't turn as fast, the effectiveness of the parts they drive may be reduced. We will keep this in mind as we proceed.

Several companies make pulleys for the Mustang; I chose ASP -- they offer an attractive set that includes a harmonic damper integrated with the new crank pulley. Other sets' crank pulleys mount in a piggy-back fashion to the factory unit, a kind of jury-rigged approach that I wasn't crazy about (you could argue that it's best to keep the factory damper in place since it's supposedly tuned to the engine, but I've yet to hear of any problems caused by a properly installed high-quality piece like the ASP -- also note that if you have a '98 Cobra, the piggy-back sets won't fit). The damper-included set lists for $199. I bought mine from Steeda -- they didn't mention in their catalog that ASP was the manufacturer, but they were the exact same parts sold elsewhere under the ASP name (at least they were back in Spring '98).

Installation

The installation is straightforward, but a couple of special tools are needed. You need a puller to get the factory crank pulley out -- I didn't have one; neither did I have an easy way to get to the alternator pulley (an impact wrench is required), so I had the friendly folks at Motion Dynamics handle the job while I was there for my subframe connector installation. I gladly paid them $35 to have the job done right (and it's definitely a job you want done exactly right -- an improperly installed crank pulley can cause major engine damage which you'll have a tough time getting fixed under warranty. It's also a good idea to check the torque on the pulley bolts periodically after they're installed).

The crank and water pump pulleys went in fine but the alternator pulley was going to be a bit harder. We were going to have to remove the alternator from the engine in order to swap the pulley since there wasn't enough clearance for the impact wrench. After a bit of discussion, it was decided to leave the stock alternator pulley in place. The new one isn't much bigger -- any performance improvement would be marginal at best -- plus if we left the stock one on, I'd be less likely to have charging problems (I'd been a little uneasy after hearing about dim headlights and dead batteries from some pulley users). Also, the factory belt was retained even though there have been some reports of belt squeal after pulleys are installed (cured by changing to a slightly shorter belt). I have experienced no such problems, however.

Impressions

It's probably a good thing that I kept the stock alt pulley, since I don't have any voltage drop at all unless I have the radio cranked, the fan on high, and the lights on when idling. As I switch on more accessories (rear defroster, foglights, etc.), the voltmeter needle does swing towards the low end (but still within the "normal" range) and my lights do dim but I doubt that I'll be in that situation very often. The other side-effect is that the motor gets hotter at stoplights or when driving hard (especially in hot weather) -- not surprising since the water pump is being driven slower. Under such conditions, the gauge creeps up into the "A" zone on the "NORMAL" scale. I reduced this problem by altering my coolant mix to 60% water/40% antifreeze and adding a bottle of Redline Water Wetter -- now the needle just gets into the "M" at its peak on the hottest days. (Another trick to use, if you see the needle creeping up when sitting in traffic, is to switch on the air conditioning. This turns on the electric radiator fan and keeps things nice and cool under the hood when you're just puttering around in town.)

If you're really concerned about overheating, you can retain your stock water pump pulley or even swap with one that's smaller than stock. A shorter belt will be needed, however, and the power gains may not be as great. Since it's not a big deal to change the water pump pulley, some experimentation may be worthwhile -- start with the underdrive unit and leave it in if your temps stay under control.

One further effect of the pulleys is that there's a bit more steering effort when maneuvering at low speeds, such as in parking lots, due to the slower power steering pump. The remaining accessory, the air conditioner, seems to cool the interior just as well as before (a good thing when you live in Texas).

Given all this, are the pulleys worth it? Well you may remember that I felt a performance increase when I put in the Roush Cold Air kit, which supposedly gives a 9-12 rwhp improvement. Again, I have no dyno or dragstrip figures, but I'd say the pulleys are giving me at least 150% of that amount. A power increase is evident throughout the RPM range; I can toast the tires under conditions where I never could before. The difference is not like night and day, but it's certainly not as subtle as with the cold air kit. The improvement is well worth the cost and all the minor side-effects I've experienced. Bravo, ASP!

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