Ad Radar
Car Craft
Click here to find out more!

572ci Big-Block - Mail-Order Strokers

Admit It, You've Always Lusted for a 572ci Big-Block and Now's Your Chance

By , Photography by Manufacturers

There are times when a junkyard 350 or even a 6.2L aluminum LS engine just isn't enough. There's an ever-growing portion of the Car Craft population that embraces wretched excess, grabs ahold of ludicrous-sized engines, and puts the power down with tire-wrinkling acceleration. The players in this vignette are not stars of the quarter-mile—they are street-burners like us. But they know that massive displacement is what shakes the ground, and there's only one real way to get there. Spend the money on a good aftermarket block, a long-arm crank, and rods, add a great set of heads, and you have the recipe for an axle-twister. Sure, you can add a centrifugal supercharger like an F2R Procharger or an 8-71, or even a pair of hair dryers for ludicrous power, but frankly an 11:1 compression 572ci Rat with rectangle port heads and a big roller cam doesn't need a turbo to flatten your eyeballs to the back of your head when you hook all that torque to a stretch of 1,320 feet of asphalt.

We've been doing some part-number archaeology and discovered that building a big-inch Rat motor has never been easier and less expensive to build than right here, right now. Sure, you'll spend $10,000 for a carburetor-to-oil-pan big-inch Rat, but these durable parts will deliver righteous power for as long as you want, and the most you might have to do is change the oil. Then when you become cozy to all that power, add a 150 shot of nitrous and that good old feeling will come right back. While 1,000+ hp looks attractive, unless you have an NHRA 25.5 chassis certification to run 7.50 at 180 mph in the quarter, along with all the other safety gear that turns your cruiser into a race car with a rollcage, it seems counterintuitive to pay for 2,500 hp you can't really use. But you can run 10 flat at 138 mph with little more than a few safety pieces and a five-point rollbar. So roll back the ridiculousness a little and let's look at what it takes to build an affordable, normally aspirated big-inch Rat motor. It's easier than you think.


Cylinder Blocks

Any big-inch Rat worth its head studs begins with a good foundation. We've just finished assembling a 496ci Rat based on a stock 454 block, and frankly, we should have spent the extra money for an aftermarket block—one with a 4.50-inch bore. Factory 454 blocks are fine at 700 hp, but if you are serious about building an axle-twisting Rat, then invest in a good block. Chevrolet Performance, Dart, World, and now Blueprint Engines all offer new castings that can get the job done. A critical point is choosing the bore size. This is where bigger is always better. The minimum you should consider is 4.50 inches. Besides better breathing from the larger bore, the advantage is to create a big-inch engine without having to add the longer stroke, which increases piston and ring wall friction and windage. You can build a 555ci Rat with a 4.56-inch bore, while keeping the stroke to 4.25 inches.


Block Party Numbers

Description Bore Deck Height Weight PN Price
Dart one-piece 4.50–4.625 9.80 250 31273444 $2,250.78
Dart two-piece 4.50–4.625 9.80 250 31273644 2,250.78
Chevy one-piece 4.50 max 9.80 269 19170540 2,299.97
Chevy one-piece 4.50–4.600 9.80 258 19212192 1,869.97
Blueprint two-piece 4.50–4.625 9.80 275 BPS4500200S 2,049
Blueprint one-piece 4.50–4.625 9.80 275 BPS4500100S 2,049
World two-piece 4.50–4.625 9.80 275 085012 2,667.05
Brodix two-piece AL* 4.50–4.600 9.80 142 8502000 5,038.97

*Aluminum block


Displacement Disco

The following are examples of the most common big-block Chevy bore and stroke combinations. If you have an idea for a combination that's not on our list, the formula for displacement is as follows:

Displacement = Bore x bore x stroke x 0.7854 x number of cylinders
Displacement = 4.5 x 4.5 x 4.5 x 0.7854 x 8
Displacement = 572 ci


Standard Deck Height: 9.80

Bore Stroke Cubic Inches
4.25 4.00 454
4.31 4.00 467
4.31 4.25 496
4.50 4.25 540
4.56 4.25 555
4.60 4.50 565
4.50 4.50 572
4.625 4.25 571
4.56 4.50 588
4.60 4.50 598

Rotating Assemblies

Did you know it costs no more to buy a 540ci Rat rotating assembly than it does for a 496? It's true. The explosion of Super Pro bracket drag racers building big-inch motors has jacked the volume so much that what used to be considered exotic drag race engine parts are now available at bargain-bin street prices. Ohio Crankshaft offers a 540/555/565 stroker rotator package that includes 4340 steel 4.250-inch crank, SRP pistons, 6.385-inch, H-beam 4340 steel rods, Total Seal rings and Federal-Mogul bearings all for less than $2,000. Bolt that spinning combo into a Dart block and for less than $4,500 you have the basis of a killer big-block. Of course, Ohio Crank isn't the only game in town. Companies like Scat, Eagle, Callies, and Crower offer packages that range widely in price, depending upon quality. We found a Scat rotator assembly with a 4340 steel crank, H-beam rods, pistons, rings, and bearings for $2,030 through Summit Racing. Like these, there are dozens of combinations too numerous to list. Variables include important stuff like metallurgy where 4340 is stronger than 5140, which is, in turn, stronger and more ductile than cast iron. Small things like rolled fillet edges for the rod journals drastically increase strength, even for a cast crank. One way to compare cranks would be to evaluate weight. A lighter rotating weight requires less horsepower to accelerate. This won't show up on an engine dyno but will reveal itself on the dragstrip or an acceleration-rate-chassis dyno, where power is extrapolated by how quickly the engine accelerates the drum. Of course, a big stroke needs counterweight to offset piston and rod mass. This is why buying a complete rotating assembly is a very good idea since the company has already done the bob-weight research.


Tall Deck: 10.20

Bore Stroke Cubic Inches
4.50 4.75 604
4.56 4.75 620
4.60 4.75 632
4.625 4.75 638


Cylinder Heads

The only reason to build a stroker big-block Chevy is to make power. The best way to get maximum benefit from all this displacement is with a great set of heads. Here is where the best money is spent in terms of dollars per horsepower. High-flowing big-block heads are not cheap, so don't be misled by the siren song of budget Chinese heads. The good stuff all comes from domestic-based companies like AFR, Brodix, Dart, Edelbrock, and TFS. There are also dozens of good race heads out there, but we'll keep our discussion centered on mainstream heads. For a 540- or 572-inch Rat, we're going to focus on rectangle-port heads with an intake-port volume of between 325 and 355cc. Cam specs will determine the peak torque and horsepower points based on intake lobe duration, but let's apply Westech's Steve Brulé's formula for power that uses 1.25 torque per cubic inch (lb-ft/ci) formula for a 10.5:1 compression, pump-gas Rat. Applying this formula (1.25 x ci = peak torque) to a 540 creates 675 lb-ft of torque. Using 90 percent of that number for torque at peak horsepower at 6,500 rpm (675 x 0.90 = 607 lb-ft) delivers 751 hp (607 x 6,500 / 5252 = 751). That's amazing power for a single four-barrel pump-gas motor.

We've listed just a few of the more impressive cylinder heads on the market today so you can get an idea of what's out there. Peak flow numbers are typically in the near-400-cfm-plus range. Our chart lists the flow at 0.600-inch lift because that's a reasonable valve lift number for a street-driven camshaft. Often these heads will flow 400-plus cfm at 0.700- or even 0.800-inch lift. For best peak horsepower, don't forget to inspect the exhaust flow numbers. One way to evaluate an exhaust port is to divide the exhaust flow cfm at a given valve lift by the intake cfm; the result will be expressed as a percentage. A rule of thumb is a good exhaust port will come in at 70 percent or above. But don't condemn a head that fails to reach this 70 percent level, but it will require more exhaust duration (more time) to evacuate the cylinder at high rpm. Also keep in mind that all big rectangle-port big-block Chevy head manufacturers will raise the exhaust port between 0.250- and 0.600-inch above the stock big-block port location. This radically improves exhaust port flow but makes it difficult to fit an off-the-shelf header. This is especially problematic when using large 21⁄8- to 21⁄4-inch primary pipe diameter headers. It's best to consider that when building a 500-plus-ci big-block those custom headers should be part of the budget.


Big-Block Head Chart

Head PN Valve Size Chamber Int. cfm at 0.600* Exh. cfm at .600* E/I at 0.600*
AFR 357 CNC 2010 2.30/1.90 121cc 383 310 80.9%
Brodix BB-3 366cc 2031006 2.30/1.88 115cc 394 277 70.3%
Dart 355cc 19574030 2.30/1.90 119cc 399 282 70.6%
Edelbrock 340cc 77409 2.30/1.90 119cc 369 241 65.3%
TFS 360 4141008 2.30/1.90 122cc 362 270 74.5%

*The cylinder-head flow numbers were taken from manufacturer published data. There are multiple variables among these numbers from different flow benches, bore diameters, and other inconsistencies that directly affect these flow numbers, so all these numbers should be used merely as trend indicators and not as hard facts. If there are enough interested readers, we could be persuaded to do a more complete rectangle-port head test in a future issue.

Induction

We won't spend a lot of time here, except that with large-displacement engines, the sheer size will make massive torque even when you build an engine where peak horsepower has the emphasis. We built a 496 a few years ago (“707 HP for $6,720,” Mar. '07) that included a cast crank, stock rods, a Comp mechanical roller 254/260-degree cam, 305cc AFR rectangle-port heads, an Edelbrock Victor, Jr, and an 850-cfm carburetor. Even with a relative big mechanical roller, this “small” Rat made 514 lb-ft at 3,000 rpm and peak torque came in at 5,400 with 603 lb-ft. So for our next 496, we've upped our game, and from our Rat-friendly friends we hear that a Dominator carburetor is worth some power. The research indicates that while 1,050 cfm seems like overkill, the wider spacing of the throttle bores improves mixture distribution and that, with the larger venturis, inlet air speed is reduced. This can be an advantage because high mixture velocities have to make that 90-degree turn from vertical to horizontal flow to enter the intake ports. Since fuel is heavier than air, the air makes the turn and fuel slams into the bottom of the intake manifold. This is why taller manifolds also help. With a Dominator carb, the slower air speed at high rpm has a better chance to make the turn. Of course, this also means that low-speed throttle response may be a little sluggish. That's the compromise with any street engine. For street use, this will also require some specific tuning to lean the idle and low-speed circuits in the carburetor to prevent running the engine excessively rich at part-throttle boulevard engine speeds.

Three-circuit Dominators have received a bad reputation as street carburetors, but the reality is that this added low-speed circuit could be leaned out just as easily as the idle circuit in order to produce acceptable part-throttle operation. This is where a wideband oxygen (WBO2) sensor can be used as an excellent tuning aid.


Short-Block Kits

Here's where the fun really begins. It is time-consuming and challenging to build your own short-block, unless you have all the proper tools for measuring, creating custom clearances, and assembling an engine. But you don't have to because there are multiple companies out there that make the difficult part easy by offering outstanding deals on assembled short-blocks. ATK has been assembling performance engines for years, and we ran across an attractive 540ci internally balanced package using a standard-deck Dart Big M block, a forged 4340 steel crank, a forged piston, and H-beam rods all for a Summit Racing price of $4,799. Given that the block goes for $2,250, this means you're getting an assembled and balanced short-block for an excellent price. This still requires the usual cam, valvetrain, heads, oiling system, and all the rest, but an assembled short-block is an excellent way to begin your big-block journey.

Along those same lines, Ohio Crankshaft offers the choice of a 509/540/555/565ci Rat using a Merlin block with a 4.250-inch steel crank, 6.385-inch H-beam rods, and forged pistons assembled for $4,395, or you can step up to a 572- or 588ci Rat still at the standard 9.8-inch deck height assembled for $4,995. Scott Shafiroff Racing is right there in the hunt with a 540ci assembled short-block that starts with a Dart Big M block, an Eagle 4340 crank and H-beam rods, JE/SRP forged pistons, and Clevite bearings all assembled for $4,595. Or if displacement envy is your thing, but with a standard deck motor, Shafiroff builds a 582ci Big Dawg motor with similar parts to the 572 for $4,845. At 1.25 lb-ft/ci, we're talking about a Rat that will twist nearly 730 lb-ft of torque. Think diesel-locomotive-level torque and then go from there.

There are many other examples, but by now you get the picture. Torque is what shoves you back in the seat in the middle of Second gear when wimpy motors have fallen off the torque curve. If we haven't got you thinking in terms of expansive valve covers and driveshaft-twisting torque, check your pulse.


572ci Big-Block Chevy

To put some real numbers to all this conjecture, Steve Brulé at Westech built a thumpin' street big-block a couple of years ago and put it on the dyno. As you can see from the numbers, this beast never fell below 600 lb-ft of torque and twisted more than 820 hp at a mild 6,400 rpm. What might really tweak the naysayers is that this was with a hydraulic roller cam. A quick rundown of the specs below includes a Dart Big M block, an Eagle crank and rods, Mahle 10.5:1 compression pistons, a Comp Cams hydraulic roller cam (271/274 duration with 0.680/0.647-inch lift and 112-degree LSA). The heads were a pair of Dart 355cc Pro-1 CNC heads with a Dart Dominator intake and a Holley 1150-cfm two-circuit Dominator carb. Brulé even used off-the-shelf roller rockers instead of an expensive shaft rocker system. This motor makes excellent torque down low and would be simple to maintain with the hydraulic rollers. This beast makes 600 lb-ft of torque at 3,200 rpm.


572ci Power

RPM Torque HP
3,200 603 367
3,400 617 400
3,600 639 438
3,800 659 477
4,000 671 511
4,200 682 546
4,400 693 580
4,600 710 622
4,800 729 666
5,000 737 701
5,200 738 731
5,400 736 757
5,600 729 776
5,800 717 791
6,000 704 804
6,200 691 816
6,400 675 823
6,600 655 823
6,800 631 817

SOURCES
Scoggin-Dickey Parts Center
5901 Spur 327
Lubbock
TX  79424
800-456-0211
http://www.sdparts.com
Blueprint Engines
Kearney
NE
800-483-4623
http://www.blueprintengines.com
Trick Flow Specialties
1248 Southeast Avenue
Tallmadge
OH  44278
330-630-1555
http://www.trickflow.com
JEGS
101 JEGS Place
Delaware
OH  43015
800-345-4545
http://www.jegs.com
Brodix
301 Maple P.O. Box 1347
Mena
AR  71953
479-394-1075
http://www.brodix.com
Eagle Specialty Products, Inc.
8530 Aaron Lane
Southaven
MS  38671
662-796-7373
http://www.eaglerod.com
Summit Racing
Akron
OH
800-230-3030
330-630-0240
http://www.summitracing.com/
Chevrolet Performance
800-450-4150
http://www.chevroletperformance.
com
Westech Performance
11098 Venture Drive
Unit C
Mira Loma
CA  91752
951-685-4767
http://www.westechperformance.co
m
Ohio Crankshaft
Greenville
OH
800-333-7113
ohiocrank.com
ATK High Performance Engines
1102 West North Carrier Pkwy
Grand Prairie
TX  75050
800-421-3746
http://www.atk-engines.com/
Scat Enterprises
3-10/-370-5501
http://www.scatenterprises.com
Dart Machinery
353 Oliver Street
Troy
MI  48084
248-362-1188
http://www.dartheads.com
Shafiroff Race Engines
35 Davinci Dr.
Bohemia
NY  11716
http://www.Shafiroff.com
Crower Cams
6180 Business Center Court
San Diego
CA  92154
619-661-6477
http://www.crower.com
Edelbrock
2700 California St
Torrance
CA  90503
310-781-2222
http://www.edelbrock.com
Callies Performance Products
901 South Union St
Fostoria
OH  44830
419-435-2711
http://www.callies.com
  • «
  • |
  • 1
  • |
  • 2
  • |
  • 3
  • |
  • View Full Article
Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
21 comments
Mike Rosato
Mike Rosato

No replacement for displacement. Big blocks rule.

Pedro Perez
Pedro Perez

Camero craft worships cameros and ls. That stuff has been way overdone

Ben Earl
Ben Earl

Dan Edwards that is a Chevy big block not an LS

Howard Cooper
Howard Cooper

decided to go old school 10.5 454 in my 73 Vette

Billy Rice
Billy Rice

Nothing beats the cackle of a blown big block Chevy on alcohol.

Dan Edwards
Dan Edwards

I'd rather see an article stroking a Fiat 500 than ANOTHER LS .

Carroll Smith
Carroll Smith

any low buck LS-3 build ups coming? seeing the cylinder heads are capable of making so much h.p in stock form

Agapito Ramos
Agapito Ramos

That would be one hell of an engine, but 10k for the average joe is hard to come by.

Patty Williams
Patty Williams

My hubby built a 572 for his 55 chevy. Awesome sound & power

Car Craft