KJ Jones
October 22, 2012
Photos By: KJ Jones

A few months and issues of your favorite Mustang magazine have gone by, and we hope you've had a chance to read and absorb the cover story of our Oct. '12 issue. In the article (“The Main Event,” p. 52), your scribe takes representative 'Stangs from four of our most popular Mustang platforms, and evaluates the percentage-difference in performance gain for each of them with bolt-ons. Our rules of engagement for that effort meant that the parts we used had to be available for each Mustang platform in our control set. Since such pieces are not yet developed for the newest 5.0 Ponies (and we doubt they will be), underdrive wheels didn't make the cut for the battle.

With that said, we're happy to announce that the underdrives' time has come, as this month we're revisiting installation and dyno test of a three-piece pulley set from March Performance (PN 1000-08; $54). While the latest 5.0-liter Mustangs are undisputedly the hotness now, we've noticed there also has been a recent resurgence for the original 5.0-powered Ponies ('79-'93 Foxes), which literally made the underdrive concept famous for our hobby.

For the uninitiated, underdrive pulleys are direct-replacement wheels of varying diameters (smaller crankshaft, larger water pump and alternator) that basically reduce the speed/rpm of such belt-driven engine accessories as the water pump and alternator. The slower pulley speed decreases the amount of parasitic drag on the crankshaft, which ultimately allows the engine to rev quicker, freeing up that engine's inherent horsepower.

While Ricardo Topete of GTR High Performance is adding the March set on a Fox this time (Max Partida's '92 Mustang LX), the installation is simialr on any applicable Pony. The following photos and captions touch on the three-piece pulley set's installation, which actually requires only an hour and handtools that are found in most 'Stangbanger tool collections, save for an impact for the alternator. In addition to those details, we also recommend you pay close attention to the dyno results, which confirm the solid gains.

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On The Dyno

Although the operation is definitely easy, installing Fox 5.0 underdrive pulleys is slightly more labor-intensive than, say, bolting on a cold-air system--slightly. However, based on the impressive and consistent horsepower and torque gains that you can pretty much count on seeing with pulleys, we have to say this particular basic upgrade (especially the steel set at less than $60) really delivers.

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Baseline March Pulleys Difference
RPM Power Torque Power Torque Power Torque
2,900146.37264.96n/an/an/an/a
3,000154.09269.76n/an/an/an/a
3,100160.33271.64166.66282.366.3310.72
3,200165.12271.01172.17282.587.0511.57
3,300170.27270.99177.97283.257.712.26
3,400176.58272.77185.11285.958.5313.18
3,500182.97274.56191.41287.238.4412.67
3,600187.62273.72197.06287.509.4413.78
3,700191.59271.96201.26285.699.6713.73
3,800194.73269.15204.91283.2110.1814.06
3,900198.08266.75207.57279.539.4912.78
4,000199.33261.72210.49276.3811.1614.66
4,100200.89257.34212.79272.5811.9015.24
4,200203.33254.26214.39268.1011.0613.84
4,300203.32248.34215.58263.3212.2614.98
4,400202.83242.11215.68257.4512.8515.34
4,500203.40237.40215.33251.3211.9313.92
4,600202.46231.17214.94245.4112.4814.24
4,700201.15224.78215.27240.5614.1215.78
4,800200.32219.19214.59234.8014.2715.61
4,900197.81212.02211.51226.7113.7014.69
5,000193.12202.86209.64220.2116.5217.35
5,100190.50196.18203.99210.0713.4913.89

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