Sometimes we instigate the engine projects featured in this magazine, other times the engines come to us. This month we're bolting together an engine that came to us on a silver platter-from Holley, no less.
Having gone on a wild company-buying spending spree in the '90s, Holley controls an impressive range of core performance aftermarket companies, and is thus able to bring many talents to bear. To showcase these capabilities, Holley asked us to take a look at its latest demo engine, and after glancing at the bill of materials pouring into Vrbancic Brothers Racing where the engine would be assembled we were happy to oblige.
The idea is to build a low-compression-8.5:1-short-block with good heads, an airflow-friendly intake, and a centrifugal supercharger to reach the magic four-digit power figure on pump gas using a blow-through carburetor system. Why not? It's a winner that appeals to many of us.
And it really is an all-star cast. The engine begins with a Dart racing block, moves on to a Lunati forged stroker crankshaft, Lunati Pro-Billet connecting rods, and Lunati forged pistons. The cylinder heads are CNC'd Pro1 Darts and mount a Holley single-plane intake, which, like the heads, is modified by Wilson Manifolds. With its stout foundation and a goal of more than 1,000 hp there was no way a hydraulic camshaft was going to cut this hot rod's mustard, so a Lunati mechanical roller was selected. With lift in the 0.660 range and up to 276 degrees duration, it ought to get the job done. The capper is a 4150-series Holley modified by The Carb Shop, a specialist outfit associated with Vrbancic Brothers Racing. Finally, making the magic is an ATI/ProCharger centrifugal F2 supercharger.
And yes-many of the companies mentioned are in the Holley fold. In fact, with the exception of the valve covers, which came from Ford Racing, nothing on the engine came from Ford.
This month, we're reviewing the parts and following the assembly on this big-power unit; next month we'll hide in the corner while the monster is dyno'd. So check out the goods in the photos, then stay tuned.
The Brothers Vrbancic
OK, let's get the obvious question out of the way first-say ver ban sick and you've got the pronunciation down. The next answer is Bob and George Vrbancic Brothers Racing is based in Ontario, California, and specializes in blow-through carburetor pushrod engines. Not necessarily Ford specialists, Vrbancic Brothers builds the usual classic domestic V-8s, often to high power levels. That means plenty of big-block Chevys, plus small-blocks from all over Detroit, including their share of stroker Windsors such as this one.
Bob Vrbancic also owns The Carb Shop, which is next door. We'll cover the Carb Shop in more detail next month in the dyno story, but for now we'll note they're Holley loyalists and have quite a reputation for building high-achieving carburetors for a wide range of street and race applications.
Vrbancic Brothers Racing is also a dyno shop for engine builders in the area. Their in-house water brake allows them to verify their own engines as well, of course, and they keep a big-block Chevy dyno mule on hand to test run 100 percent of The Carb Shop's work. So, with their Holley connection, dyno, and big-power experience they were a shoe-in to build Holley's stroker Windsor demo engine.
Not only stoutly built, the Dart block features a 9.500-inch deck height and is available in 4.00- or 4.125-inch-bore versions, so max displacement is easily supported. Holley's is a 4.125-inch version to easily allow the final 427ci displacement. The Dart blocks are a couple thousandths taller than nominal to allow a cleanup pass over the decks by the engine builder.
Distressingly minimal cylinder-wall thickness has been a Ford V-8 issue for decades, but the Dart Iron Eagle block puts that concern to rest. As this view of the bottom of a cylinder shows, generous wall thickness remains after boring-a claimed 0.250-inch with a 4.185-inch bore. Likewise, the deck minimum thickness is 0.675-inch. These are siamesed blocks as well, so Vrbancic doesn't even bother to sonic-check them. The downside is, the 9.500-inch Windsor Iron Eagle weighs 195 pounds.
"Stout" describes the Lunati crankshaft. Designed as more than a heavyweight, big-cube crankshaft, the unit features internal balancing and 2.748 inches, Cleveland-spec main bearing, and 2.100-inch rod-journal diameters, so it isn't afraid of rpm.
We found the Lunati crankshaft nicely detailed. The leading edges are bull-nosed and knife-edged to reduce windage, and overall the finish is high for a production crank. Weight reduction commensurate with high strength is evident; the rod throws feature blind lightening holes, and the centerline of the entire shaft has holes. This does nothing for rotating weight, but it does help reduce total engine mass.
Again using Lunati's best, these are the Pro-Billet LAG2 6.200-inch SB Billet Rods. Hewn from solid chunks of 4340 steel, they weigh 675 grams and came in a box marked to indicate they had been balanced to our specific crankshaft, so they were part of a crank kit. That saves time having parts balanced in the field. If such a 1,200hp billet rod is a bit much for your needs or wallet, Lunati also offers a less expensive forged Pro-Street rod, or the same rod with increased finishing work as the Pro-Mod.
The Lunati piston forgings are built to take a pounding. The -38cc dished crowns help attain the blower-friendly 8.5:1 compression ratio, and from the looks of the battleship thick edges there's no issue with thin spots between the rings and valve reliefs here. Piston weight is a beefy but manageable 506 grams; the diameter is 4.122 inches.
Destined for straight-line work at the dragstrip, the Holley engine uses a simple wet-sump oiling system inside a Milodon deep-sump pan with matching pickup. A stock-type Melling M-83HV high-volume 351 oil pump fits the Dart block's four-bolt mains without issue (but it did get close to the crankshaft-more on that later). The heavy-duty oil-pump driveshaft is an IS-83, also by Melling.
"Big" would be a succinct way to describe the Lunati mechanical-roller camshaft. Carrying grind number 10-UR15-UR94, this cam muscles up 0.668x0.668-inch valve lift with 1.6 rockers, and sports 265 degrees intake x 276 degrees exhaust duration at 0.050-inch tappet lift.
Plenty of tricks are visible in this piston close-up. The compression height is 1.300 inches with the pin out of the oil ring, and all sorts of anti-flutter grooves are visible in the piston sides. Given the huge cylinder pressures this engine will see, the top piston rings were fattened up from the standard 1.2mm Total Seal rings Lunati normally uses on these pistons.
Huge-lift cams in big power engines tend to be driven by belts because of the cam/crank isolation the belt drive offers. Furthermore, a belt drive such as this Jesel KBD-34170 offers easy cam-timing adjustments via a two-piece cam sprocket, and cam changes are a bit easier, too. Expect to use an electric water pump and definitely an electric fuel pump with a belt drive.
Dart Pro 1 cylinder heads got the nod for this 1,000hp engine. With 225cc intake and 87cc exhaust ports, and an exhaust port raised 0.135-inch, these heads are nearly in the all-out race-head category. They feature a 62cc combustion chamber and a 2.08x1.60-inch valve package. Unlike a pure race head such as a Yates, these castings provide easy fitment to both the short-block and engine compartment.
Wilson Manifolds fully ported the Dart heads to ensure maximum power production. The extent of the porting shows here, where the port wall has been cut enough to break into the pushrod passage and the valveguide has been streamlined. These heads were completely covered by the CNC machine, too. Every nook in all 16 ports and 8 combustion chambers received machining treatment.