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5.3L LS Small Block Build - Whipped Into Shape: Part 4

Modern Mouse, our 5.3-liter LS engine, gets a dose of boost courtesy of Whipple.

By Richard Holdener, Photography by Richard Holdener

Since our 383 was no longer a simple 5.3L truck motor and lacked any of the accessories, including the manual water pump, Whipple decided to supply its 2.9L "Tuner" kit (lacking components like the flash tool, air filter, and misc. hardware). The highlight of the kit was obviously the 2.9L W175ax (front-feed) supercharger, but every bit as important was the integrated air-to-water intercooler core. Heat is a natural byproduct of compression, which is another way of saying that all forms of forced induction heat the inlet air supplied to the motor. The higher the boost, the higher the associated inlet air temperature. One of the tried and true methods of decreasing the heated inlet air temperature is to pass it through an intercooler. Whether air-to-air or air-to-water, intercoolers are designed to eliminate a portion of the unwanted heat. The Whipple system employed an air-to-water intercooler core positioned directly below the discharge of the supercharger in the lower intake manifold. Twin-screw superchargers are highly efficient, meaning they minimize the unwanted increase in air temperature, but that doesn’t mean they won’t benefit from intercooling. The only thing better than boost is intercooled boost.

As with all superchargers, the boost supplied by the Whipple was a function of two things, the normally aspirated power output and blower speed relative to engine speed. The blower speed was controlled by the drive ratio between the crank and blower pulleys. As the drive pulley, an increase in diameter of the crank pulley will increase boost pressure while the opposite was true of the blower (or driven) pulley.

Wanting some adjustability, we requested a variety of different blower pulleys to work with the supplied ATI crank pulley. Though it was likely overkill at this boost and power level, Whipple supplied a 10-rib pulley system to eliminate any chance of belt slippage. We may put them to the test at a later date with Modern Mouse, but for now it was nice to have a repeatable boost curve run after run. Whipple offers kits for a variety of different LS applications, ranging from trucks and SUVs to the LS3 Camaro. Our kit featured (or required) the water pump and pulley offset from a 2011 Camaro. A cool alternative would be the 2010 Camaro electric water pump offered by Meziere (see photo).

Initially the Whipple supercharger was set up with a 3.875-inch blower pulley. According to the company website, this pulley combination was designed to provide 10 psi of boost (at 6,500 rpm) to a stock 6.2L LS3 Camaro engine. On our modified 383 (6.27L) stroker, the pulley combination netted a peak boost pressure of 7.4 psi. Run with a pump-gas tune (18 degrees of timing and 11.5:1 air/fuel), the supercharged combination produced 671 hp and 598 lb-ft of torque. A splash of 100-octane allowed us to safely crank up the timing to 22 degrees, where the same pulley combination produced 718 hp and 626 lb-ft of torque.

The supercharged motor responded very well to additional ignition timing, but care must be taken not to get too greedy. The power output of a supercharged motor often continues to increase with ignition timing right up to the point where all the magic smoke comes out. Detonation is quick and decisive and can ruin a perfectly good combination regardless of the presence of forged internals. Running just 7.4 psi, the Whipple increased the power output of the normally aspirated 383 from 541 hp and 518 lb-ft of torque to 718 hp and 626 lb-ft.

The question now was who wouldn’t be happy with a motor making over 700 hp? The answer was (obviously) a guy looking for 800 hp! Knowing there was more power to be had from this supercharged combination, we decided to do what all blower owners do—crank up the boost. In just a few short minutes, off came the 3.875-inch blower pulley and on went the smaller 3.625-inch pulley. The smaller blower pulley increased the peak boost pressure supplied by the Whipple to 9.6 psi and the power output right along with it. The supercharged 383 now produced 778 hp and 672 lb-ft of torque. Being so close to the 800hp mark, we decided to go for it. Rather than increase the boost, we decided to simply install a set of larger 1-7/8-inch headers from American Racing. Thinking that a motor exceeding 775 hp would benefit from additional exhaust flow, we installed the larger headers. We also added 1 degree of timing to the top of the curve. Our efforts were well rewarded as Modern Mouse thumped out 804 hp and 682 lb-ft of torque at a peak boost reading of just 9.2 psi. The increase in exhaust flow was responsible for the drop in boost pressure. There was obviously more boost and power available from the Whipple supercharger, but even at its present power level, any Ford going up against Modern Mouse will be totally screwed!

Comp Cams
3406 Democrat Road
TN  38118
Trick Flow Specialties
1248 Southeast Avenue
OH  44278
Probe Racing
2555 West 237th Street
CA  90505
Whipple Superchargers
3292 N. Weber
CA  93722
Procomp Electronics
605 S. Milliken Avenue
Unit A
CA  91761
L&R Automotive
13731 Bora Drive
Sante Fe Springs
CA  90670
By Richard Holdener
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