The only other change to the 440 was replacing the camshaft with a grind more suited to a blown application. The Supercharger Store recommends a wider-than-normal lobe separation angle to optimize the engine for boost. This is a fairly general recommendation that follows established practice with blown engines, serving to open the exhaust valve sooner, and reduce overlap. In theory, opening the exhaust valve earlier helps deal with the greater volume of gasses produced with supercharging. The reduced overlap is beneficial since overlap scavenging is not critical for cylinder filling with a blower providing the fill. The wider lobe separation is well accepted, so we bit and replaced the cam, going from a 110-degree lobe separation to 114, with no other changes in cam specs. We have not done a back-to-back test of lobe separation angles to verify the benefit, but we'll go out on a limb and say it probably isn't necessary in most cases with typical street cams.
With the engine reassembled, what was left was simply bolting on the blower kit. The Supercharger Store needs to be complimented on the completeness of the kit, since every nut and bolt we needed came in the box, with no runs to the hardware store required. Essentially, an adapter bolts to the damper to take the lower pulley, and then the blower bracket is mounted in place. Next, the blower bolts onto its mounts, and from there it is just a matter slinging the belt in position and plumbing. With their street kits, a blow off valve is fitted to the inlet tube. For high capacity "race" systems, a large, high-flow, blow-off valve is provided, which we got with our kit. The valve needs to be "T-ed" into the induction pressure pipe, and this requires welding an included tube and flange in place.
THE TESTIt was an exciting day when our 440 arrived at Westech for testing. The blower gave the engine a serious look that suggested there was going to be quite a display of power. We trimmed the 440 out with a set of high-flowing TTI stepped headers, and an MSD distributor and wires firing top-notch Denso Irridium plugs. Both exhaust flow and ignition are areas not to be neglected when courting blown horsepower. We plumbed in The Supercharger Store's water injection system (see sidebar), and filled the reservoir tank with a dilute water/methanol mixture, actually windshield washer fluid. It all looked like a go, and sure enough, the 440 fired and settled nicely into an idle. Taking a conservative approach, the ignition timing was set to just 25 degrees total advance, about 10 degrees less than the best normally aspirated power setting.
To establish a baseline before running the engine in the blown configuration, the engine was shut down, and the blower belt and air hat were removed. We ran a baseline and found 421 hp at 5,600 rpm, over 125 hp less than the best numbers this engine has shown before. With the two-point drop in compression ratio, the 4-degree wider lobe separation, and the 10-degree retarded timing, it was not surprising. The belt was reinstalled, and we were ready to try boosted power. Initial problems involved getting enough fuel flow from the carburetor to supply an adequate mixture. Eventually, we installed the largest 4150 carb we had available, a Race Demon RS, with 1,050-cfm venturi sleeves, fitted with power valves at both ends, and very large jets. We were only making short static pulls at a given rpm point and boost level, to gage air/fuel mixture up the range. We were experiencing some variation in boost levels, compounded by a lack of repeatability, which was causing difficulty with tuning, especially at higher rpm. Dyno operator Tom Habryzk suspected belt slippage. We cranked the belt tensioner and continued.
We carried on with the power sweeps and saw quite a bit of boost variation from run to run. Tom pointed out that the serpentine belts could become problematic with high boost and big blowers. To help the situation, the belt was coated with VHT "Track-Bite," and the tensioner wound until the belt was as tight as a violin string. We saw as much as 757 hp at 5,700 rpm and 13.5 psi of boost, but belt slip, even with all of these measures made it a problem to let the engine run up. Finally, the belt skipped a rib, and ended our test session. We later discovered that the blower pulleys were not in perfect alignment, which may have aggravated the situation. We should have checked that, since there are shims from The Supercharger Store to readily adjust the alignment. However, Tom pointed out that in his experience with many large centrifugal blowers in higher boost applications, serpentine belts are often problematic, maintaining that a cogged belt drive is the only way to go.