Over the past few weeks, we’ve taken a short look at Borowski Race Engines’ 2.9-liter Whipple supercharged LS engine package. It’s a brute, but there’s another engine you might find interesting, and that’s their front drive Whipple 4.0-liter twin-screw blown LS. It’s a take-no-prisoners package and if you have an insatiable need for speed, then this one should be right up your alley!
The bottom end of the Hellfire power plant closely parallels the 2.9-blown version we examined previously. It all begins with a Dart LS Next cylinder block. We’ll review some of it here:
According to Borowksi’s Ken McCaul: “The LS Next block is the first significant change in the bottom end architecture of the LS engine platform. By eliminating the ‘Y-block’ design and utilizing conventional style main caps and oil pans (stock pans can be used with Moroso oil pan spacers), Dart has addressed the problems resulting from the LS engine’s separated crankcase bays. Windage is greatly reduced, resulting in increased power and improved lubrication.
“This design change led to several additional improvements. The main webs are significantly stronger because the bay-to-bay breathing windows are eliminated in Dart’s design. Deleting the windows also allows the cylinder barrels to be extended by .3750” into the crankcase, providing greater piston support at the bottom of the stroke.
“All stock and aftermarket LS components can be utilized. Conventional style 4-bolt steel main caps are used. A 5/8” thick full deck design is utilized for superior strength, with six head bolts per cylinder to provide secure clamping. Dart’s priority main oiling system ensures high rpm reliability and includes provision for oil restrictors in the lifter valley.”
The reciprocating assembly parallels that found in the 2.9-blown engine (which speaks volumes for the component strengths we’re talking about). For example, the crankshaft is the same 4.00-inch stroke forged Callies Dragonslayer used in the 2.9-blown LS. It’s mated to a set of coupled with 6.125-inch (center to center) Callies Ultra Connecting rods. Callies manufactures these rods from extremely clean Timken steel that is formulated to their exact specifications. Then the proprietary steel is forged in a Trenton, Michigan facility, and 100% completed in Callies’ Fostoria, Ohio facility.
The 10.25:1 pistons are custom Diamond piston 2618-alloy forgings. This material is perfect for high boost or nitrous applications (hence the use here in supercharged LS). These pistons feature 3D milling on piston tops. Additionally, they’re an inboard forging design and they have a pin offset for quiet operation. The skirts are moly coated to reduce friction and to improve skirt wear. The top ring is down 0.250-inch and the ring grooves measure 1.2-mm x 1.2-mm x 3.0mm.
The ring package is also the same as the 2.9-liter ground pounder and it too comes from Diamond (Pro Select AP Steel Rings). Ditto with the wrist pins are also from Diamond – they’re heavy duty 0.200-inch thick examples manufactured by Diamond’s sister company, Trend. And finally, the bottom end also relies upon Clevite HN rod and HX main bearings.
Like the 2.9, the 4.0-liter blown LS relies upon a custom designed hydraulic roller camshaft manufactured by Bullet Cams. And on a similar note, the camshaft specs are proprietary. Finally, the hydraulic lifters are off-the-shelf, matching tie bar configuration jobs from Bullet.
Borowski Race Engines incorporates a stock LS timing cover along with a Cloyes hex-adjust adjustable timing set. Identical to the 2.9 combination, the 4.0-liter blown LS Dart block works with a custom Borowski Racing-engineered aluminum oil pan along with a custom pickup to provide the correct sump pickup depth. Ditto with the oil pump, which is a Melling-sourced piece fitted with a custom relief spring.
As you can see, the foundation is stout (and it has to be). In our next issue, we’ll wrap it up with a detailed look at the top end. The power production is serious. Watch for it.