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STATS
| | SMEDING 572 SPECS |
| ENGINE TYPE | big-block Chevy |
| DISPLACEMENT | 572 ci |
| BORE X STROKE | 4.630x4.250 |
| COMPRESSION RATIO | 10.0:1 |
| DECK HEIGHT | 9.800 |
| ROD LENGTH | 6.535 |
| MAIN BEARING CLEARANCE | 0.0022-0.0025 |
| ROD BEARING CLEARANCE | 0.0022-0.0025 |
| CRANKSHAFT ENDPLAY | 0.007 |
| PISTON TOP RING ENDGAP | 0.022 |
| PISTON SECOND RING ENDGAP | 0.020 |
| PISTON COMPRESSION HEIGHT | 1.140 |
| PISTON DOME VOLUME | -5 cc |
| PISTON-DECK CLEARANCE | 0 |
| HEAD GASKET COMPRESSED THICKNESS | 0.043 |
| COMBUSTION CHAMBER VOLUME | 115 cc |
| VALVE DIAMETER | 2.300/1.880 |
| VALVESPRING DIAMETER | 1.625 |
| VALVESPRING SEAT PRESSURE | 275 pounds |
| VALVESPRING OPEN PRESSURE | 810 pounds |
| CAM SPECS | 252/262-at-0.050; 0.613/0.613; 112 |
| CARB SIZE | 850 cfm |
| FUEL TYPE | 91 octane |
| MAIN CAP BOLT | 110 lb-ft |
| ROD BOLT | 70 lb-ft |
| HEAD BOLT | 75 lb-ft |
 To seal the combustion chambers,...  To seal the combustion chambers, the 572 relies on a set of 0.043-inch-thick Cometic multilayered steel gaskets. Matched with a zero-decked block, the result is a tight quench clearance for improved power output and detonation resistance. Transferring lobe lift to the pushrods are Smeding hydraulic roller lifters.  What makes the 572 really...  What makes the 572 really thump is a set of Airflow Research 325cc aluminum cylinder heads (PN 2101). They boast 2.300/1.880-inch valves, 115cc combustion chambers, and killer as-cast intake ports that flow an incredible 384 cfm. Smeding runs them straight out of the box, and the results speak for themselves. They were torqued down to 75 lb-ft with ARP head bolts.  It’s the little things that...  It’s the little things that count. The intake rocker studs on many big-block Chevy heads protrude into the port. To prevent oil from leaking into the ports, Smeding applies thread sealant onto the intake rocker studs.  Bumping open the valves are...  Bumping open the valves are a set of Scorpion 1.7:1 aluminum rocker arms, which are actuated by Manley pushrods. Yet another benefit of keeping the rpm down is the ability to run pedestal-mount rockers instead of much pricier shaft mounts. For nice and quiet operation, the rockers were tightened to three-quarter turn past zero lash.  Feeding the cylinder heads...  Feeding the cylinder heads is an Edelbrock Victor Jr. single-plane intake manifold (PN 2902). While dual-plane manifolds are more common in engines that are tuned for torque, a single-plane works great in this application thanks to the 572’s massive displacement.  Although 4500-series carbs...  Although 4500-series carbs work great on race motors, they’re not always the best choice for street motors. As such, the Smeding 572 comes equipped with a Quick Fuel Technology 4150-series carb that moves 850 cfm. On the dyno, the tune proved excellent right out of the box.  Although it’s more of an issue...  Although it’s more of an issue with longer stroke motors, torsional vibration is an inevitable by-product of the internal combustion process. To smooth things out, the Smeding 572 relies on a Pro Race torsional damper.  Providing the spark for the...  Providing the spark for the big Rat is a Smeding billet distributor and plug wires. The timing was set at 14 degrees of initial advance and 32 degrees of total advance.  The owner of this particular...  The owner of this particular 572 ordered up the optional Concept One serpentine drive system. For an extra $2,295, this slick setup includes a billet alternator, power steering pump, A/C compressor, brackets, and pulleys.  Once in the dyno cell, the...  Once in the dyno cell, the 572 was hooked up to a set of 2-inch primary headers with 3-inch collectors. Wideband oxygen sensors monitored the air/fuel ratio on both banks of cylinders, which registered between 12.0 and 12.5:1 throughout the WOT pulls.  Tuning an engine for max power...  Tuning an engine for max power on the dyno is the norm, but Smeding goes one step further by tuning for driveability as well. This is accomplished by tinkering with the air bleeds, jetting, and mixture screws.
BY THE NUMBERS |
| RPM | TQ | HP |
| 2,600 | 602 | 298 |
| 2,700 | 618 | 318 |
| 2,800 | 635 | 339 |
| 2,900 | 647 | 357 |
| 3,000 | 658 | 376 |
| 3,100 | 661 | 390 |
| 3,200 | 663 | 404 |
| 3,300 | 664 | 417 |
| 3,400 | 668 | 432 |
| 3,500 | 672 | 448 |
| 3,600 | 677 | 464 |
| 3,700 | 686 | 483 |
| 3,800 | 696 | 504 |
| 3,900 | 708 | 526 |
| 4,000 | 721 | 549 |
| 4,100 | 731 | 570 |
| 4,200 | 737 | 589 |
| 4,300 | 739 | 605 |
| 4,400 | 740 | 620 |
| 4,500 | 740 | 634 |
| 4,600 | 737 | 646 |
| 4,700 | 737 | 659 |
| 4,800 | 736 | 673 |
| 4,900 | 732 | 683 |
| 5,000 | 729 | 694 |
| 5,100 | 724 | 703 |
| 5,200 | 721 | 714 |
| 5,300 | 716 | 722 |
| 5,400 | 708 | 728 |
| 5,500 | 700 | 733 |
| 5,600 | 692 | 737 |
| 5,700 | 679 | 737 |
| 5,800 | 666 | 736 |
| 5,900 | 652 | 732 |
| 6,000 | 637 | 728 |
| AVG: | 692 | 570 |
Most engine shops only tune for peak performance at WOT, but the problem is that street motors operate at part throttle most of the time. As such, Smeding takes exhaustive measures to tune each of its crate engines for maximum driveability. Unlike many dynos that can only control throttle, Smeding’s DTS unit can place load on an engine independent of throttle input. In other words, the DTS dyno has one handle for throttle control and a separate handle for load control. “After we break in a motor, we set the idle mixture and ignition timing. Next, we increase rpm to 2,000, put 100 pounds of load against the motor, then check the air/fuel ratio again,” Ben Smeding says. “We want the air/fuel ratio to be in the mid 13s during this part of the tuning process. Next, we increase the load to 150 pounds, with a target air/fuel ratio of low 13s. We repeat the procedure at 2,300 rpm, and vary the load between 100 and 150 pounds, tweaking the air/fuel ratio as necessary with the air bleeds, jets, and mixture screws. Optimizing the fuel mixture in this range is what makes an engine driveable. If a motor is too rich or too lean at cruising speeds, it will run dirty and hesitate. The squirters don’t do much when you gently roll into the throttle, so they can’t cover up a carb that’s out of tune. After the tuning for driveability is complete, we never touch the primary side of the carb again, and only alter the secondaries when tuning for max power.”
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