Underdrive Pulley Swap & Torque Converter Performance Test

Do Speed Parts Really Work Edelbrock Intake And Carb Making Horsepower

Underdrive Pulley Swap
Price: $71.95
How Much Faster?: 0.159 seconds/1.51 mph
Underdrive pulleys are popular speed goodies for late-model cars but, you really have to wonder if they're worth anything, you know, speedwise. Well wonder no more, because we tested them on a '92 Mustang GT with a five-speed manual trans. For consistency, we ran on 26x8.5-15 Mickey Thompson E.T. drag slicks mounted on stock 15x7-inch Mustang wheels. Our testing regimen included launching the car at 3,000 rpm and shifting at 5,500 rpm. With the tall 3.08:1 gears, we were able to go through the lights in Third gear at about 5,000 rpm. We made four back-to-back runs for a baseline and four back-to-back runs after the pulleys were installed. The best before-and-after runs are shown below. Our testing proved the pulleys are worth at least a solid tenth on the strip-cheap speed when you consider they're available from such companies as R&E Racing for well under $100. -Miles Cook

Petersen ad guy Justin Fort's otherwise bone-stock 128,000-mile tester had a few minor updates, including a Moroso air intake system and a DynoMax 2 1/2-inch exhaust system running through a stock H-pipe. The only non-engine add-ons were Saleen wheels, a set of Maximum Motorsports adjustable lower control arms, and Maier Racing subframe connectors.
Petersen ad guy Justin Fort's otherwise bone-stock 128,000-mile tester had a few minor upd
Bolting on the pulleys is quite straightforward. Be sure to loosen the four crank pulley bolts, the four water pump pulley bolts, and the alternator nut while the belt is still under tension.
Bolting on the pulleys is quite straightforward. Be sure to loosen the four crank pulley b
Underdrive pulleys are available for just about any late-model GM or Ford. Our test pulleys were made by Auto Specialties and the three-pulley set (above) includes crank, water pump, and alternator pulleys. To slow down the water pump and alternator, the crank pulley is smaller and the other two are larger than the stock pulleys (below).
Underdrive pulleys are available for just about any late-model GM or Ford. Our test pulley

Performance Testing
Description	E.T.	MPH	Improvement
Stock pulleys	14.334	95.15	Baseline
Underdrive pulleys	14.175	96.66	-0.159 sec/+1.51mph

Source
Auto Specialties
Dept. CC
13313 Redfish, Ste. 106
Stafford, TX 77477
281/261-5811

R&E Racing
Dept. CC
44533 N. Sierra Hwy.
Lancaster, CA 93534
805/948-7622

Torque Converter Test
Price: $300-$800 (depending on tranny type and stall speed)
How Much Faster?: 0.384 second/1.04 mph
Here's a speed tip: If your car has an auto trans, launch it at the track by holding your left foot on the brake while bringing up the engine rpm. When the light goes green, stop braking and gas it-if traction is good, the car will almost always go quicker than if you leave off idle. Why? The engine reacts better from the increased rpm, and the torque converter is working to better multiply torque.

It's a bit more complicated than that, but you can take further advantage of the same phenomenon with an aftermarket torque converter to supply both a higher stall rpm and increased torque multiplication. But swapping converters is a pain, so we needed to know if the aggravation is worth it. We used the Cheap Street Chevelle to find out.

Our 3,840-pound '70 Chevelle is fitted with a GM 502/502 big-block crate motor (513hp/555 torque), a JET 4L80E overdrive tranny, and a 12-bolt with 3.73:1 cogs. The 4L80E used a stock 14-inch, 1,400-rpm-stall converter so we swapped in a converter with a stall of 2,000 rpm. The 4L80E trans drives the price up-our Pro Torque converter was $795-but prices for older three-speed autos are often much cheaper. -John Kiewicz

Performance Testing
Description	E.T.	MPH	Improvement
Stock 1,400-rpm stall	12.419	108.45	Baseline
Pro Torque 2,000-rpm stall	12.035	112.45	-0.384sec/+1.04 mph

Sources
JET Performance
Dept. CC
17482 Apex Cir.
Huntington Beach, CA 92647
714/848-4200
www.jetchip.com
(4L80E tranny swap kit)

Pro Torque
Dept. CC
1440 Church St.
Bohemia, NY 11716
516/218-8700
www.protorque.com
(4L80E torque converter)

The stock GM 4L80E converter (left) generated a weak 1,400-rpm-stall speed behind our 502 big-block, whereas a Pro Torque 4L80E converter can be custom built to deliver a stall speed ranging from 2,000 to 4,000 rpm while still incorporating the electronically controlled lock-up feature. Pro Torque is one of only a few companies offering a performance converter for the beefy 4L80E.
The stock GM 4L80E converter (left) generated a weak 1,400-rpm-stall speed behind our 502
Although stall speed is important with a performance torque converter, more important is the converter's torque multiplication rate. Pro Torque builds custom converters with special late-model ('95 and newer) internals rather than using rebuilt older converters with '60s-'70s fluid-routing technology. As a result, Pro Torque's converters are said to deliver a 2.3:1 to 2.4:1 torque multiplication rate rather than the standard 1.7:1 to 1.8:1. Pro Torque's 10.5-inch converter weighs only 35.6 pounds compared to the porky, stock 14-inch converter at 57.8 pounds.
Although stall speed is important with a performance torque converter, more important is t
Raising the stall from 1,400 to 2,000 rpm allowed the engine to rev just enough to dip into the fat part of our 502's torque curve. Wearing a set of Mickey Thompson 26x10.5-15 rear meats the Chevelle improved its e.t. from a 12.419 to a 12.035-a 0.40 improvement from a 600-rpm-stall increase!
Raising the stall from 1,400 to 2,000 rpm allowed the engine to rev just enough to dip int