The bottom of the engine assembly is finished off with simple, stamped steel oil pan and timing cover. The all-black finish will contrast nicely with the aluminum heads and intake that will come next. The bottom of the engine assembly is finished off with simple, stamped steel oil pan and t As we mentioned, Dart's prediction for our project engine was 668 hp and-drum roll, please-that's exactly what we got: a peak of 668 hp at 6,000 rpm (668.9 horses, to be more precise). And while the dead-on prognostication was impressive, even more so was the overall performance of our big-bore 509. With its strong low-end torque and deep-breathing heads, the engine quickly started making big power. It crossed the 400hp level by 3,600 rpm and hit 500 by only 4,400 rpm. By 5,100 rpm it was making 600 hp and it kept pulling to nearly 6,500 rpm-that's some serious revs for a big-block street/strip engine and one of the primary reasons we were interested in exploring the big-bore/short-stroke combination. Maskin, who's had decades of experience building racing engines, was philosophical about the results. Or, to put it another way, he wasn't surprised. "We've been doing this a long time," he says. "We know what other engines of larger and smaller displacements make with the same basic components, so estimating the horsepower pretty much comes down to the displacement of the combination." His confidence was reassuring and we were enthused to find our project engine exceeded expectations on all fronts. We already have an idea of what we're going to do with the engine, but that's another story for a future issue. Dart suggested its aluminum Pro1 310cc cylinder heads and we didn't argue. It's the intake runners that measure 310cc, but Dart offers them in capacities up to 345cc. The intake port location is stock to match standard intake manifolds, but the exhaust ports are raised. 0.300-inch for greater flow and the easier installation of larger diameter headers. Dart suggested its aluminum Pro1 310cc cylinder heads and we didn't argue. It's the intake The fast burn-style combustion chamber design of the Pro1 heads promotes quicker, more complete combustion. The chamber volume is a relatively larger 121cc. Both the intake and exhaust valves are rolled 2 degrees from stock: 24 degrees vs. the stock 26 degrees on the intake side and 15 degrees vs. 17 degrees on exhaust side. The intake valves measure 2.250 inches in diameter, while the exhausts are 1.880 inches. The fast burn-style combustion chamber design of the Pro1 heads promotes quicker, more com Dart threw on relatively new Ultra Pro Magnum roller rockers from Comp Cams (1.7 ratio). Interestingly, they're steel, not aluminum-a feature selected for its strength and long-term durability. In fact, their 8650 chrome-moly steel material is, according to Comp Cams, 300 percent stronger than typical aircraft aluminum rockers. To keep the weight down, they have an open design and the black finish looks pretty cool, we think. Too bad they'll be hidden by the valve covers. Dart threw on relatively new Ultra Pro Magnum roller rockers from Comp Cams (1.7 ratio). I One of the other interesting details of our project engine is the use of Dart's patented, adjustable pushrod guide plates. The self-locking fasteners enable super-easy adjustments with a variety of valvetrain components. Why didn't we know about these years ago? One of the other interesting details of our project engine is the use of Dart's patented, With the valvetrain set, worked moves to the induction system. It starts with another part designed and manufactured by Dart: the intake manifold. To match the airflow capability of the heads and short-block, it's a cavernous, open-plenum design that shines at high rpm. The raised water crossover and air gap design insulate the air/fuel charge from engine heat, too, while integrated bosses in the runners are there if we ever get the urge to spray our big-block. With the valvetrain set, worked moves to the induction system. It starts with another part For dyno testing, Dart's builders bolted on this Demon 850cfm four barrel. It features 1.560-inch venturis and 1.750-inch throttle blades. Jetting specs include #85 on the primary with a power valve and #93 on the secondary jet and no power valve. The comparatively easy adjustability of the Demon design is appreciated on the dyno. For dyno testing, Dart's builders bolted on this Demon 850cfm four barrel. It features 1.5 Here's the completed engine, dressed and ready for testing on Dart's dynamometer. Note the 1-inch spacer between the carb and intake, as well as the 2.125-inch (inside diameter) test headers. And while this engine represents a custom build for Super Chevy, it uses nothing but off-the-shelf parts and Dart's standard short-block components. It could be duplicated with a simple phone call. Here's the completed engine, dressed and ready for testing on Dart's dynamometer. Note the The prediction for the engine was 668 hp and after a couple of trial/tuning pulls, the engine cranked out 668 hp. In fact, it was 668.9 at 6,000 rpm. Peak torque was 623 lb-ft at 4,500 rpm. Heck, it was making 500 lb-ft just off idle, so foregoing a longer stroke for larger bores hardly disqualifies this as a torque motor. It just happens to rev easily to 6,400 rpm. The prediction for the engine was 668 hp and after a couple of trial/tuning pulls, the eng ON THE DYNO RPM HORSEPOWER* TORQUE (LB-FT)* 2600 260.3 523.8 2700 276.7 538.1 2800 299.8 562.3 2900 320.7 580.8 3000 337.8 591.6 3100 347.0 587.7 3200 355.1 582.7 3300 366.1 582.7 3400 377.2 582.7 3500 389.6 584.6 3600 404.7 590.3 3700 419.1 594.9 3800 438.7 600.3 3900 440.4 601.3 4000 459.4 606.7 4100 479.4 611.8 4200 485.5 613.1 4300 498.2 615.7 4400 519.6 620.3 4500 533.8 623.0 4600 541.5 618.6 4700 553.5 618.6 4800 564.0 617.1 4900 578.5 620.1 5000 592.5 622.4 5100 603.2 621.3 5200 611.6 617.7 5300 620.3 614.6 5400 634.4 617.0 5500 643.6 614.6 5600 653.3 612.7 5700 652.4 601.1 5800 654.1 592.4 5900 653.1 581.3 6000 668.9 585.5 6100 658.2 566.8 6200 636.3 539.1 6300 620.3 517.1 6400 625.3 516.7 SOURCES Dart Machinery 353 Oliver St. Troy MI 48084 248-362-1188 www.dartheads.com « | 1 | 2 | View Full Article By Barry Kluczyk Enjoyed this Post? 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