The folks at Borowski Race Engines have extensive experience with all sorts of engine combinations, and recently they turned their attention to the LS platform. EngineLabs detailed a 427-cube build naturally-aspirated earlier, and now the Borowski boys are at it again, this time with a 4.0L Whipple supercharger.
The engine uses the Dart LS Next engine block, a piece designed to fix what Dart’s Dick Maskin, feels are the shortcomings in the LS platform, namely the oil system’s consumption rates as discussed in this article.
The LS Next block uses traditional Gen I style main caps and oil pan rails while retaining the rest of the LS architecture, and Borowski’s engine builders have started to take these builds to the next level.
An internally-balanced Callies Magnum crankshaft and Callies Ultra H-beam connecting rods work in conjunction with a set of custom Diamond pistons to achieve the displacement.
Friction is kept to a minimum thanks to the double pin oilers in the pistons, the coated Dart cam bearings and Clevite HN connecting rod and HX main bearings.
Cylinder heads are RHS six-bolt LS7 Pro Elite models with a 291cc intake port, necessary for the level of boost this engine was designed for. The heads feature an improved 12-degree valve angle and raised runners that provide a smoother flow path into the cylinders. The six-bolt design takes advantage of the six-bolt platform on the LS Next engine block to provide superior sealing, critical in any boosted application. The heads also have a .750-inch-thick deck to prevent movement under power.
With a 4.75-inch drive pulley on the supercharger set up to provide 12 pounds of boost, the engine cranked out 975 horsepower – on pump gas. They later dropped the supercharger drive pulley down to a 3.625-inch size, added C16 race fuel, and the Holley EFI engine management system was able to control this monster as it made 1,155 horsepower.
Custom Diamond LS pistons have been designed specifically for Borowski’s needs.
“We decided the blown combination of our 427 package would be best served with a shorter connecting rod – 6-inches long – with a 4-inch stroke and 4.125-inch bore to achieve the displacement. The reason for using the shorter rod is that it allowed us to work with Diamond to build a custom piston that gives great ring support for the big boost. With the longer rod, the piston is so short there’s just not a lot of compression distance there to provide ring support,” explains Borowski’s lead engine builder, Dave Livesey.
“The shorter rod lets the piston gain compression distance, and although you lose a bit of rod-to-stroke ratio, it was more important to us to have the piston strength in this application,” he continues. “There’s a lot more meat between the top and second rings, which is so incredibly important with the LS engine. With these pistons, our final compression ratio on this engine is about 10.25:1. We overbuilt the engine – it’s capable of handling up to 30 pounds of boost, and although this supercharger won’t do that, if the customer wanted to, it could make 25 pounds pretty easily on this combination.”