KJ Jones
June 17, 2013
Contributers: KJ Jones
Ricardo Topete of GTR High Performance puts the final tug on the 78.5-inch serpentine belt of Luis Chavez’s Kenne Bell-blown ’03 Cobra, after replacing the stock idler pulleys with a slick new four-piece set from DivisionX Performance.

It's Terminator time here. Yes, we know this doesn't happen all-too often here in Tech Inspection. However, it's with good reason that we haven't focused much on quick bolt-ons for Ford's first-born supercharged 'Stangs.

Our '03-'04 Cobra coverage is limited because the basic bolt-on formula for improving stock Terminators' performance is well documented: Install a cold-air-intake system, install a smaller supercharger pulley, and recalibrate the PCM. Opening up the exhaust is considered the final phase of basic. Then upgrades turn more elaborate, such as replacing superchargers and adding built long-block assemblies.

While decreasing the diameter of the blower pulley gets unanimous approval as an instant gratifier, there's another easy, complementary measure—including a set of billet idler pulleys. Replacing a Snake's three OEM 90mm idlers, doesn't necessarily require the smaller blower wheel, and it isn't a bonafide power-gaining upgrade. However, the replacement falls right in line with affordable, basic mods that do make a positive difference to an '03-'04 Cobra's engine performance by eliminating belt slippage and helping make boost more consistent.

DivisionX Performance offers a four-piece, billet-aluminum, idler-pulley system available via Lethal Performance that brings much-improved belt wrap to Terminators. The system [PN DX-5111-B (black) or DX-5111-C (clear); $409.99] features three CNC-machined, 100mm idler wheels which directly replace the stock 90mm pieces, and one 90mm wheel. The latter idler sits just to the lower-right (when facing the engine) of the supercharger pulley, and acts as an additional tightening force on the belt.

When we queried Ricardo Topete of GTR High Performance about viable candidates for this month's TI, Luis Chavez's '03 Cobra immediately came to to mind. While the GTR crew had recently upgraded it with a 2.8-liter Kenne Bell supercharger, the factory idler pulleys weren't delievering optimal belt traction.

The following photos and captions present the major points in the 30- minute pulley replacement. This DIY-friendly effort requires only a 3⁄8-inch breaker bar (for removing and installing the serpentine belt), and sets of standard sockets and Allen wrenches for tools. When it's all said and done, the DivisionX dual-bearing idlers provide a stronger platform for belt travel, and a much cleaner look on the front of a Terminator's engine.

These are the three stock idler pulleys on the ’03-’04 Cobra’s accessory drive system. Notice the pattern on the face of each wheel? Traces like this are typically caused by water that gets into the bearings (after a car or engine wash), and is spun out at high speed when the engine is running. The dried water markings also bring forward the possibility that there may be rust or scoring on the single bearings inside each pulley.

This is the complete set of DivisionX ’03-’04 Cobra idler pulleys, which are available from Lethal Performance. The CNC-machined 100mm and 90mm aluminum idlers, as well as the billet bracket (for the 90mm wheel) are designed to put extra tension on the supercharger belt, which helps prevent belt slip and lost boost. The system includes high-grade hardware and dust covers for each pulley, and is available with a black- or clear-anodized finish.

Swapping a Terminator’s idler pulleys is a fairly simple task that can be performed in a driveway or home garage. After removing the serpentine belt, the three OEM pulleys are removed.

Here’s a side-by-side look at the stock 90mm idler pulley and one of the new DivisionX idlers that we’re installing on Luis’ Snake. While clearly different in diameter, the pulleys share the same width.

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The factory 90mm idler pulleys all are of stamped-steel construction, featuring only one center bearing, which offers limited support and is susceptible to failure at high rpm. Notice the scoring on the left side of this bearing? We warned you this might have happened. This type of damage is common when water comes in contact with idler pulleys, and also when Cobras are fitted with bigger blowers. The damage is a perfect example of why including an upgrade like this with your move to more boost is a good idea.

And by contrast, all of the DivisionX pulleys are supported by dual bearings, which help make the new idlers much stronger than factory pieces, and better-suited for high rpm and high boost.

The beautifully crafted, 90mm pulley mount is designed to attach to the timing cover, and sit in the channeled section of the Terminator engine’s pulley crossover bracket. A replacement fastener is provided for the front cover; the upper arm of the bracket is secured to a front-cover stud that also supports the engine’s coolant tube.

In a span of less than 30 minutes, Ricardo has the DivisionX four-piece idler pulley installed on this Kenne Bell-blown engine. The pulleys bolt on without requiring any modifications to the timing cover, and we’re sure their larger-than-stock diameter (100mm) along with the extra support wheel (90mm), will virtually eliminate belt slippage when Luis goes to exercise his Snake’s 550 hp. 5.0