Smeding Performance 572 Crate Motor - The 700 Club
Smeding Performance concocts a 572 crate motor that kicks out 737 hp and 740 lb-ft without even trying!
From the June, 2012 issue of Chevy High Performance
By Stephen Kim
Photography by Stephen Kim
Every motor Smeding Performance...
Every motor Smeding Performance builds is tuned for max power and driveability on the dyno. Complete from carb to oil pan, the Smeding 572 Extreme crate motor includes a polished timing set and valve covers, and lists for $12,995.
Holy heaps of lb-ft, Batman, this 572 Rat is wicked. Although Robin has a reputation for getting excited far too easily, there’s good reason for his enthusiasm this time around. The Smeding Performance 572ci crate big-block presented before us makes 692 lb-ft of torque, but that’s not the impressive part. That 692 figure isn’t peak torque, but rather the motor’s average torque throughout its entire 2,600- to 6,000-rpm rev band. Yikes. Peak torque checks in at 740 lb-ft at 4,400 rpm, and better yet, the massive Rat kicks out 700-plus lb-ft from 3,900 to 5,000 rpm. Now that’s what you call kicking some serious heinie throughout a very broad rpm range. That said, man does not live by lb-ft alone, and torque without horsepower is nothing more than a glorified dump truck motor. Fear not, for the Smeding big-block backs up its impressive torque tally with 737 hp. Can you say block-long burnouts with 2.73:1 gears? Now this is our kind of motor.
The Smeding 572 Extreme crate motor certainly has all the right stuff. It’s based on a Dart Big M block, and fitted with rugged forged internals. Up top, Airflow Research 325cc aluminum cylinder heads, an Edelbrock Victor Jr. intake manifold, and a Quick Fuel Technology 850-cfm carb provide the air supply while a mild COMP 252/262-at-0.050 cam kicks the valves open. Nevertheless, anyone can bust out their checkbook and order up a pile of nice parts. It’s the ability to select the right components and engineer a fundamentally proficient combination that separates the fly-by-night hacks from the experienced pros.
The key to squeezing 572 ci...
The key to squeezing 572 ci out of a package that’s identical in external size to a 396 is a siamesed-bore Dart Big M block. Smeding punches the holes out to a massive 4.630 inches. When matched with a 4.250-inch stroke, the result is 572 delicious cubes in a standard 9.800-inch deck block. Dart performs most of the machine work prior to shipment, so the only prep work required is boring and honing the cylinders, and align-honing the mains.
As Ben Smeding explains, big peak numbers aren’t everything. “It’s only natural to look at the peak horsepower and torque numbers that an engine makes, but we build our combinations for the widest powerband possible. “We try to maximize torque as low as 2,500 rpm because when you mash the gas at cruising speed, you want the motor to respond,” he says. This approach also means that the 572 produces peak power at 5,700 rpm, and is ready to shift by 6,000, reducing stress on the bottom end and valvetrain while increasing durability. Quite frankly, we were shocked to see the 572 big-block crank out 737 hp considering that it’s rated at 690 hp. “We dyno our motors using regular pump gas we buy down the street, and day-to-day variations in fuel quality and ambient air conditions can impact power output. As such, we underrate our motors to leave a safety margin for these variables. The bottom line is that we want to make sure that our customers are happy, and they’re getting all the horsepower that they’re paying for.”
By virtue of underrating one of its crate engine packages by 47 hp, Smeding Performance might just be one of the most honest engine shops in the business. As you might expect from such an outfit, the price of admission for this 572 is pretty darn reasonable as well. Complete from carb to oil pan—including the distributor and plug wires—the Smeding 572 Extreme lists for $12,995. We’re all for getting your hands dirty and building an engine yourself, but matching this kind of performance for the dollar is no small feat. DIY builds don’t come with three-year, unlimited-mile warranties, either.
While many 572 big-blocks...
While many 572 big-blocks utilize 4.500x4.500-inch bore and stroke dimensions, Smeding opts for a larger 4.630-inch bore and a shorter 4.250-inch. The big bores unshroud the valves for improved cylinder head breathing, and the short stroke reduces piston speed and friction at any given rpm. Smeding’s own 4.250-inch forged 4340 crank provides the additional stroke.
Rounding out the rotating...
Rounding out the rotating assembly are steel 6.535-inch Smeding H-beam rods, and forged 10:1 KB pistons with a 1.140-inch compression height. Smeding says that using a relatively short rod increases the rod angularity during the power stroke, thereby increasing the force exerted on the crankpin and boosting torque.
Sealing the bores are a low-friction...
Sealing the bores are a low-friction 0.043-, 0.043-, 3/16-inch ring package. The top rings are gapped at 0.022 inch, while the second rings check in at 0.020-0.022. In theory, running relatively tight ring gaps and bearing clearances, in conjunction with a standard volume oil pump, prevents oil from slinging around in the crankcase and into the combustion chamber. Combined with low-tension rings, Smeding reports that these tricks are good for a solid 25hp increase.
The rods and crank ride on...
The rods and crank ride on Clevite bearings. The clearances might seem a little tight at 0.0022 to 0.0025 inches, but the objective is to improve oil control.
By letting the cylinder heads...
By letting the cylinder heads do the hard work, the cam specs can be kept conservative to improve driveability and idle quality. The custom COMP Cams hydraulic roller features 252/262 degrees of duration at 0.050 and 0.613/0.613-inch lift.
After internally balancing...
After internally balancing the rotating assembly and installing it into the block, the main caps were tightened down. Another perk of using a conservative 4.250-inch stroke is that the rotating assembly clears the block and cam without any grinding. Since rpm is limited to 6,000, the standard Dart main bolts are plenty strong enough, and studs aren’t necessary.
By setting bearing clearances...
By setting bearing clearances on the tight side, there’s no need for a high-volume oil pump. Smeding uses a Melling standard volume unit on the 572, and opens up the mounting holes just a tad so it will slide onto the block more easily.
Lining up the dots works just...
Lining up the dots works just fine in a stock rebuild, but in high-performance builds like the Smeding 572 degreeing the cam is a must. The COMP hydraulic roller is ground on a 112-degree lobe separation angle, with 2 degrees of advance built in. After dialing in the cam, a COMP double-roller timing set was bolted in place.
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.