First, Legere attacked the con-rod issue by specifying a thorough regimen of shot-peening. After magnafluxing the OE rods for cracks, he requested S-230 shot be applied at a greater-than-average intensity range of 0.012-0.015A-compared with the more typical range of 0.006-0.012A for automotive applications. Consultation with Automotive Racing Products resulted in replacement rod bolts for the Sentra which could be easily customized to fit in order to deliver almost 50 percent more clamping force (on the basis of a torque spec at 30 lb-ft). Legere ordered a final balancing of the rods to bring them to within a single gram of weight differential.
At the big end of the rods, Legere shaved 3.25 lbs from the OE crankshaft, particularly by trimming the counterweights. At the other end, Legere worked with Venolia to make custom pistons, sized 1mm overbore, which would produce a 10.53:1 compression ratio-an almost 10 percent increase. With the engine's original stroke of 88mm left intact and its new bore of 77mm, the Sentra now displaced 1,639cc.
To address the issue of cylinder head flow, Legere negotiated between two conflicting circumstances. Oversize valves weren't an option. For budget reasons, Mather elected to retain OE valve dimensions, measuring 30mm/intake and 24mm/exhaust. And because Mather was also determined to keep the Sentra streetable, radical porting wasn't going to happen either. Legere then specified only mild enlarging and reshaping to produce 25 percent more exhaust flow (at 83.5 cfm) and 13 percent more intake flow (at 115.5 cfm). This brought the exhaust-to-intake proportion up to slightly more than 72 percent, or within reach of the 75-80 percent optimal range.
As for valve timing, Legere had no choice but to regrind the OE cam since no suitable aftermarket cams were available for this type of project. For both intake and exhaust lobes, the new lift grew to 0.354 inches at the valve with duration of 212 degrees at 0.050 inches cam lift. Legere wanted the OE springs shimmed at the lash caps to increase seat pressure and prevent valve float. Moreover, he specified the intake lobes be offset-ground by two degrees-"to tighten up the static lobe separation a bit," he explains. "Keep in mind that Nissan's variable intake cam timing constantly changes the lobe separation angle, depending on engine load and rpm." As a result, defining precise camshaft dimensions for varying operating conditions becomes something of an inexact science.
With help from the folks at Richard DeCormier Nissan in Manchester, Conn., the Sentra's engine was finally buttoned together. After a good bit of trial and error, Legere and Mather retained the OE fuel injectors, but upgraded to the larger SR20 throttle body. A 3-inch inlet pipe, K&N filter and cold-air box completed the intake plumbing. On the exhaust side, Legere designed and fabricated a custom four-into-one header boasting 36-inch primary tubes of 1.5-inch diameter, merging into a 2.25-inch collector. A 2.25-inch mandrel-bent downtube leads to two Simons Racing mufflers from Sweden. Both Mather and Legere admire the Sentra's hearty exhaust note. "When folks ask who made the sound system for my car," Mather says with a wry smile, "I just tell 'em, 'Simons Mufflers.'"
Plug wires are from Magnecor, and ignition timing is 15 degrees BTDC, or five degrees advanced from OE specs. Although the flywheel is stock, the pressure plate is 30 percent stiffer and it mates to a sprung-center disc with semi-metallic pads. The final drive ratio is 4.471:1, which is bolted to a customized limited-slip differential.
Both front and rear suspension feature the stock strut-type geometry, although the front towers have been raised 1.5 inches for increased wheel travel. Mather installed custom remote reservoir shocks from Leda. Surprisingly, the brakes retain OE discs up front and drums at the rear. The front calipers are Airborne Coated, and the plumbing is braided S.S. line from Earl's. As for wheels, they're 13 inchers-but don't bother trying to keep up with Mather's 18 different sets of wheel/tire combos that range from ice tires to 9-inch slicks and virtually everything else in-between.