We've seen lots of articles about underdrive accessory pulleys for late-model cars, but you may not be aware that March Performance also sells them for carbureted performance applications. In the case of the long-water-pump small-block Chevy, you've got a choice of Performance Ratios or High Water Flow Ratios in either V-belt or six-rib-belt designs. Either way, you can use March's high-performance alternator brackets, as seen on this month's cover, to replace the ungainly stock bracket. While March always recommends High Flow pulleys for stroker applications such as the HT383, or for nearly any real street car, we decided to compare them to the Performance Ratio set on the dyno. March warned that the biggest power gains are seen when underdriving accessories such as power steering, smog pumps, and air conditioning, but we tried them with an alternator alone. First came the Performance Ratio, and to our surprise, it made perhaps one horsepower less than the electric water pump. Call that testing variance. For practical purposes, it was the same. However, the High Flow Ratio must truly flow more water, since it drew an extra 7 hp and 7 lb-ft on average throughout Vie curve. We'd gladly give that up for the extra cooling; it's nothing like the horror stones we've heard of losing 20 hp to a water pump

This Is the trick six-rib-belt setup from March; It tends to slip less and throw belts off less than a V-belt setup. Regardless of your choice of belt style, we wholeheartedly recommend the March alternator bracket. It's far better looking than the stock bracket more rigid, easier to adjust, lighter, and won't cause hassles with the intake-manifold design like a stocker can.

The difference in ratios is obvious. The Performance Ratio uses a 5 1/2 crank pulley with a 6 1/4-inch water-pump pulley (0.88:1), and the High Flow has a 7-Inch crank pulley and a 5 1/2 on the water pump (1.27:1). For example, at 5,500 rpm, the Performance setup spins the water 4,840 rpm; the High Flow moves it at 6,985 rpm.