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Chevy Stroker Kits Insight - Long-Armed Bandits

Small-Blocks Are The New Big-Blocks, And Big-Blocks Are Now Approaching 800 ci. How Big Do You Want To Go?

Stephen Kim Mar 1, 2009
0903chp_01_z Chevy_stroker_kits_insight Stroke_close_up 2/20

The displacement train has left the station, and it passed ridiculous two blocks ago. Like the nation's staggering $10 trillion debt, the cubic inch explosion is nowhere near slowing down. Deck heights keep growing, cylinder walls keep thickening, and crank throws keep orbiting farther and farther away from their mains. To make it all fit, cam bores are creeping closer to the deck, and oil pan rails continue spreading outward. While this isn't breaking news by any means, have you checked out the possibilities lately?

0903chp_02_z Chevy_stroker_kits_insight Crankshaft_close_up 3/20

The stalwart small-block Chevy, whose architecture yielded just 265 ci when it was introduced to the public, can now be built as large as 468 ci using readily available off-the-shelf components. In response to mice encroaching on its turf, big-blocks can easily displace 665 ci these days without breaking a water jacket. Perhaps most astonishing of all is how far the displacement ceiling has been raised. Once the exclusive territory of full-race mountain motors, big-blocks boasting a capacious 5.000-inch bore spacing are now available in a user-friendly package with shelf cranks and cylinder heads to match. That means a 780ci big-block can be built using plain-Jane mail order parts, and the thought of seeing one stuffed inside a Chevelle has us giggling like a bunch of AIG executives.

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In an ideal world of unlimited budgets and nonexistent deadlines, we'd be able to assemble dozens of different motors for the sake of hands-on research. Unfortunately this isn't the case, so what we can't assemble in steel and aluminum we've instead assembled in words and pictures. While it's impossible to outline all of the different bore and stroke dimensions that can be combined to achieve a near-infinite number of displacement figures, we have compiled a list of the most popular setups. By divulging some basic tips on how to assemble a massive stroker short-block and explaining the pros and cons of various combinations, we can point you in the right direction.

Make Room
Every stroker short-block requires a certain degree of clearancing. Exactly how much and where depends on many factors, such as deck height, rod length, the shape of the rod itself, cam location, oil pan design, the length of the stroke, and block design. Nonetheless, there are several universal steps that can be taken to minimize the clearancing required by opening up as much space inside the motor as possible. Two of the easiest ways to accomplish this is with a small base-circle cam and aftermarket rods that feature profiled beams and bolt shoulders. Furthermore, large-capacity aftermarket oil pans free up additional space as well. These measures will significantly decrease the likelihood of the rods smacking into the camshaft or oil pan. Perhaps the most effective method of simplifying a stroker buildup, if your budget permits, is with an aftermarket block. With wider distances between the pan rails and raised cam locations, they minimize the grinding at the bottom of the cylinder and give the cam much-needed breathing room.

Quick Notes
What We Did

Got the scoop on stroker kits

Bottom Line
Going bigger is easier than you may have thought.

Cost (Approx)
$600 on up

Some consider the venerable 383 antiquated, especially in light of the near-500ci potential of modern small-blocks, but the 383 is arguably the simplest stroker motor to build. Essentially a 0.030-over 350 with a 3.750-inch stroke, the 383's extra cubic inches are almost free when compared to the cost of retaining a stock 3.480-inch stroke. Gone are the days of digging up a 400 crank out of the junkyard and grinding down the mains to fit inside a 350 block. The 3.750-inch stroke small-block Chevy crank, whether cast or forged, is one of the most popular aftermarket cranks ever produced. Furthermore, the relatively short stroke allows fitment of rods up to 6.125 inches while still retaining 1.000-inch of compression height with a standard 9.000-inch deck height. "The rod bolts will hit the cam whenever duration exceeds about 220 degrees at 0.050 lift, but a small base-circle cam eliminates that problem," explains Judson Massingill of the School of Automotive Machinists. "Other than that, when using an aftermarket oil pan, the only other clearancing required is some minor grinding at the bottom of the cylinders when using a factory block."

If you manage to luck out amongst the dwindling supply of production 400 blocks or have the means to ante up for an aftermarket piece, matching a 3.750-inch crank with a 4.155-inch bore nets 406 ci. The advantages of this arrangement are gloriously over-square dimensions and ease of assembly right on par with a 383. The large bore helps unshroud the valves and coax extra cfm out of the cylinder heads, while the short stroke reduces piston speed and friction.

Adding an extra 0.125-inch of stroke to the ubiquitous 383 yields a total of 396 ci, and adding another 0.125-inch of stroke on top of that (4.000 inches total) results in 408 cubes. Realistically, these two displacement combinations are as large as you can go with a stock 350 block due to cylinder wall thickness and internal clearance issues. While some intrepid enthusiasts have successfully bored 350 blocks as large as 0.060 over, few will sonic-check well at that bore size, and overheating and block integrity can become issues even if there is sufficient cylinder wall thickness. In other words, the six bonus cubes you'd stand to gain by punching a 396/408 another 0.030 over aren't worth it.

Perhaps the biggest drawback of building a 396 or a 408 is the amount of additional clearancing required. "A 3.750-inch crank fits in a production block beautifully, but a 3.8750- or a 4.000-inch crank is a real pain to work with," says Judson Massingill from the School of Automotive Machinists. "When grinding the block to clear the rods, it's very easy to hit water." Moreover, compared to a 383, the longer stroke pushes the wrist pin higher up in the piston for any given rod length and results in a less favorable rod-to-stroke ratio. That said, if you're willing to put some extra effort into your stroker build, the 396 and 408 represent the ultimate in production-block-based power potential. In theory, the additional cubic inches and stroke should pay dividends in torque production.

Once you step up to an aftermarket block, new opportunities abound. The 4.000-inch crank that's such a bear to fit into a production block drops inside an aftermarket unit easily, thanks to spread-out oil pan rails, a raised cam location, and in some instances pre-clearanced cylinders. Likewise, thick cylinder walls can be bored to 4.125 or 4.155 inches with room to spare, netting a total of 427 and 434 ci, respectively. Taking a page from the infamous Rocket block's playbook, aftermarket castings from Dart, World Products, and Brodix can be had as tall as 9.300 of deck height inches. That extra space allows the use of longer connecting rods, which means that the pistons aren't pulled as far down the bore, further reducing clearancing requirements. Thanks to the flexibility afforded by commodious aftermarket blocks, there are very few drawbacks to these two big-bore combinations.

The mystique alone may be enough to convince many enthusiasts to build a 454 ci small-block. Like its legendary big-block brother, that displacement total can be achieved with bore and stroke dimensions of 4.250 and 4.000 inches, respectively. While most aftermarket block manufacturers advertise a maximum recommended bore of 4.185 inches, World Products sells complete crate motors based on its Motown blocks that are bored to-you guessed it-4.250 inches. Obviously, with the small-block Chevy's 4.400-inch bore spacing, that doesn't leave much meat between the cylinders, even with Siamesed bores. However, cutting-edge innovations in gasket technology make a tight cylinder seal possible. "I wouldn't hit it with a power-adder, but with a multilayer steel gasket you shouldn't have any problems running a 4.250-inch bore in a small-block Chevy," Judson states.

For those who aren't entirely comfortable with paper-thin cylinder walls, stepping up to a 9.300-inch deck height block affords the same 454ci total by combining a 4.185-inch bore with a 4.125-inch stroke. Both Dart and Brodix offer blocks that have plenty of clearance for the massive stroke this combination requires. Match that lengthy stroke up with a 4.250-inch bore, and the displacement hits an astonishing 468 ci. Both 454's and the 468's have the obvious appeal of mega inches, and companies such as Eagle, Callies, and Ohio Crankshaft actually stock 4.125- and 4.250-inch cranks on the shelf. However, cranks with such long strokes sometimes become difficult to balance, as their shortened counterweight heights-necessary in order to clear the piston skirts-often require adding lots of mallory. Furthermore, 4.185- and 4.250-inch bore pistons will most likely be custom items.

Much like the 383 small-block, the 496 is downright puny by today's big-block standards. On the other hand, it is stupid-easy to put together and can be built from an abundant supply of cheap factory blocks piled up at junkyards. The formula is simple: Clean up a 454 block 0.060 over to 4.310 inches, and drop in a 4.250-inch stroker crank. Whether paired with 6.135- or 6.385-inch connecting rods, the 496 leaves plenty of piston material above the wristpins at the big-block's standard 9.800-inch deck height, which is a nice insurance policy if big power-adders are in the cards. And due to its sheer popularity, there are dozens of shelf pistons in varying compression heights to choose from. "At most, you might have to touch up the bottom of the cylinders slightly to fit a 4.250-inch stroke into a 454 block," Judson explains. "It's an old-school combination, but it still works very well."

Although it was never plopped into a production car, the hot rodding community went berserk when GM introduced the 4.468-inch Siamese-bored 502 big-block. Engine builders promptly punched the block out to 4.500 inches, threw in a 4.250-inch crank, and scored an easy 540 ci. Since they are basically 496s with a larger bore, 540s are just as easy to build. They require minimal clearancing and have tons of shelf pistons available in varying compression heights. Better yet, the 502's greatest asset is its rugged construction. Revisions GM implemented into the 454 block to create the 502 include reinforced deck surfaces for improved head gasket sealing, and four-bolt main caps. Racers have been known to push the 502 block well beyond 1,000 hp with surprisingly reliable results. Even if you can't find a good deal on a used 502 block (PN 10237292), they're available from Summit brand new for under $1,800. More often than not, it won't cost any more to build a 540 than a 496. It's no wonder why the 540 has become one of the most common big-block combinations built today.

And it gets even better. GM advises against boring a 502 block beyond 4.500 inches, but it's typical for racers to punch them out to 4.560 inches without any hiccups, netting a total of 555 ci. Boring the Rat out any more requires an aftermarket block, but a 4.600-inch bore in conjunction with a 4.250-inch stroke equates to 565 ci. Again, off-the-shelf pistons are plentiful for 4.500-, 4.560-, and 4.600-inch bores, and these seriously large holes can assist in cylinder-head breathing tremendously.

If hood clearance is an issue, or you seek to build something ultra-stealth, the 582 is the hot ticket. A 4.375-inch stroke is about as large as a standard 9.800-inch-deck-height block will accommodate, but standard-deck aftermarket blocks swallow them up without a fuss. Combined with a massive 4.600-inch bore, the result is 582 ci. Compared to a 540, the downside is that it requires an aftermarket block, so plan on coughing up a few extra bucks to play in this arena. However, the extra dough buys an extremely stout bottom end begging for a power-adder. This is yet another combination that can be built entirely from shelf parts, and there's just something sinister about packing close to 600 ci in a package that looks externally identical to a miniscule 396.

With the max bore pegged at 4.600 inches, increasing the deck height to 10.200 inches is the only way to gain additional displacement after the 582 mark. If you have the space underhood, this opens up several options. A 4.500-inch crank nets 598 ci, while a 4.750-inch unit tallies up 632 cubes. Furthermore, ponying up for a 10.700-inch-deck block allows running a 5.000-inch stroke, bringing the displacement grand total to 665 ci. The number of parts suppliers at this level shrinks a bit, but there are still plenty of shelf components to make it all happen. Both Dart and Brodix have 10.200- and 10.700-inch-deck blocks with raised cam locations that will clear up to a 5.000-inch stroke, and Callies offers the necessary cranks. Shelf pistons are readily available for the 598 and 632, while the 665 will most likely require customs. To keep the rod/stroke ratio reasonable, rod lengths from 6.700 to 7.100 inches are highly recommended. The only real hitch here is cost, spending the necessary funds to bolt on a set of cylinder heads that can keep up with the voracious appetite of this many inches.

Although we doubt we'll ever see one of these in anything that remotely resembles a street car, we sure hope someone proves us wrong. By spreading out the center mains in its 5000-series aluminum block, Brodix has increased the Rat motor's 4.840-inch bore spacing to 5.000 inches. In conjunction with a 11.600-inch deck and cam bores that have been raised a full inch, this behemoth can ingest a 5.500-inch crank. Matched with a 4.750-inch bore, that's good for 780 ci. The truly wacky part about it is that Callies stocks the cranks needed for this combo in its warehouse, although custom pistons are a must. Brodix has a set of heads that flow 557 cfm and will bolt right up, and Brodix is currently working on an intake manifold as well. At a hair under $7,000 just for a block, a combo like this is cost-prohibitive, to say the least.

Pricing It Out
To get a better idea of what it costs to assemble a stroker short-block, we've priced out a couple of theoretical buildups. Although it sometimes gives you less flexibility in spec'ing out your combo exactly how you'd like, purchasing bundled rotating assemblies is a great way to save cash. The Powerhouse 434 rotating assembly used in our small-block build includes a 4.000-inch forged 5140 crank, 6.000-inch I-beam rods, forged pistons, rings, bearings, a flexplate, and an SFI balancer. For our big-block build, we opted for a Scat 540 rotating assembly featuring a 4.250-inch forged 4340 crank, 6.385-inch H-beam rods, forged pistons, rings, bearings, a flexplate, and a balancer. Furthermore, since it makes little sense these days to monkey around with machining a production block, we've based these builds on aftermarket units instead.

Much to our surprise, our final tally was less than expected. The 434 rang up a total of $3,353, while the 540 set us back $4,475. Out of curiosity, we compared our figures to comparable turnkey short-blocks on the market. Again, the difference was less than expected. Coast High Performance sells a Dart-block-based 427 with forged 4340 internals for $4,620. Factor in the cost of professional assembly and its higher-grade internals when compared to our 434, and the $1,267 price difference is almost a wash. Likewise, Coast's Dart-block-based 540 with forged 4340 internals lists for $5,000, just $380 more than our theoretical buildup. The bottom line: If a reputable shop offers a turnkey short-block with similar specs to what you're thinking about building, it may not cost that much more than building it yourself.

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Cubic inches alone won't get you very far, which is why Brodix has a set of heads up to the task of feeding the beasts its spread-bore blocks are bound to create. These 14.5-degree castings feature 2.520-inch intake valves and flow 557 cfm, good for close to 1,200 hp.


Summit Racing
Akron, OH
Coast High Performance
Torrance, CA 90505
Delaware, OH 43015
Kellogg Crankshaft
Jackson, MI 49202
RPM International
Cerritos, CA 90703
Northern Auto Parts



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