OK, LS engines are arguably one of the best, if not the best, engines ever fielded by GM, or anyone for that matter. But sometimes they just feel a bit sterile and “soulless.” Maybe what you need is something a bit more retro, and nothing says, “old-school performance,” like a supercharged big-block. We’re not talking one of those fancy centrifugal blowers either, but a good old roots-style huffer. Knowing you want a big-block with a blower sitting majestically on top is only half the battle. You also need to make sure you properly size the supercharger to your mill. This is where hot rodders often make mistakes. Most people think in terms of boost and don’t consider how much atmosphere the unit is capable of moving. It also happens that when they see a blower that’s advertised as providing an X percent increase in power, they just assume it will translate to their engine. Maybe it will, maybe it won’t. Keep in mind that when a manufacturer states that a blower will give a certain power increase, the amount is based on a specific engine combination and doesn’t apply to a variety of engines. A small blower may give you that 40 percent boost in power on your nearly stock 396, but it just won’t move enough volume to give you the hoped-for results on a built 454 or 502. It’s akin to the law of diminishing returns. The bigger the engine, the smaller (percentage wise) the gain will be at a given boost level; at least until you step up to a bigger blower. At that point the cycle repeats. So the small 177 Weiand might be just the ticket for your 396, while that 454 or 502 might be better served by a 6-71, and even larger engines might require a monstrous 8-71 supercharger. Also, you might be better off running a larger blower and spinning it slower since this generates less heat. So, an underdriven 8-71 will most likely make more power than an overdriven 6-71. Try and follow this rule of thumb: A larger volume blower will typically make more power than a smaller volume unit at the same boost level.
To put this theory to the test we built up a Dart 454 big-block, grabbed a couple of Weiand blowers, and headed over to Westech Performance in Mira Loma, California, for some dyno time on their Superflow 902.
01 As shipped, Dart blocks (PN 31263644, $2,544) are pretty clean, but they do require some TLC. JR Twedt, owner of JR Competition Engines in Escondido, California, explained, “We deburred all the casting flash, which can eventually chip away, causing heat and stress risers.” Extra-thick siamesed cylinder walls resist cracking and have improved ring seal, scalloped outer water jacket walls help improve coolant flow, stronger steel caps incorporate splayed outer bolts, and improved lifter valley head bosses are just a few of the refinements. Other items, like true “priority main” oiling and a crank tunnel pre-clearanced for big strokes just make life easier.
02 The rotating assembly came as a kit, so our first step was to mate the Engine Pro H-beam forged rods (6.135-inch) with the KB pistons. With that done, JR custom-fitted the Hastings rings.
03 After wiping down the cylinder walls with a light coat of oil, JR went about stabbing the rod/piston assemblies into the Dart block. Since we will be running boost on this engine, our targeted compression ratio was 9.0:1.
04 We then installed and secured the Eagle 4340 forged crank. The Dart block came with high-grade main cap bolts, which saved us a few bucks.