When it comes to boring and stroking the venerable 302 small-block beyond its factory 4x3-inch dimensions, two swollen displacements have become commonplace: 331 and 347 ci. Both rely on 4.030-inch bores, the largest tunnels safely attainable within the constraints of the factory-style 302 block's water-jacket configuration. The familiar and popular 347 usually swings a 3.400-inch stroke, while the 331 typically gets by with 3.250 inches.
Now it's time to add another chapter to the poked-and-stroked 302 story. For those seeking maximum cubes from an 8.2-inch deck height, Dart Machinery now crafts a large-bore, 363ci short-block from proven high-strength components. As we'll see, this thing packs a ton of potential into a compact package.
The key to Dart's big-displacement-from-a-small-package is the whopping 4.125-inch cylinder diameter permitted by the Siamese-bore configuration of its cast-iron SHP engine block. Siamese-bore architecture eliminates water jacket voids found between the cylinders of production-style blocks, thus safely allowing larger bores while greatly increasing structural rigidity. To ensure cooling efficiency, Dart's block design provides generous water passages in the distinctive scalloped areas above and below the cylinders.
All this should sound eerily familiar if you read our recent piece (Brawn Dart, Aug. '11, p. 72) on Dart's 427ci small-block (that one was based on 9.5-inch-deck, 351W architecture). In that buildup, we finished off the 427 short-block with a relatively mild hydraulic-roller cam to create a multi-role torque monster that simultaneously churned out over 600 hp. This time around, Dart's engine gurus were anxious to get a little more racy with the bumpstick specs to show the world what their "little" 363 could do when wound up. You should find the results interesting...
For those seeking maximum cubes from an 8.2-inch deck height, Dart Machinery now crafts a large-bore, 363ci short-block from proven high-strength components
363ci Stroker Build
One thing about spending time in Dart's engine dyno cell-you don't have to spend much time there, as these guys have setup and testing honed to an art, including properly jetted and calibrated carbs (though their 750-cfm unit was missing in action, so we ended up going straight from a 650 to an 850.) On startup, we couldn't help but grin at the rumpity-rump idle attitude exhibited by the project's healthy solid roller camshaft, and the smile only widened under the mighty symphony of high compression as the big-inch small-block quickly wound north of 7,000 rpm.
The combo seemed to run best at 33 degrees of total timing, and remember that the following numbers were generated using nothing more than 93-octane pump fuel. Bottom line? With either carb, Dart's overachieving 363 managed to produce more than 1.7 hp per cubic inch! Ladies and gentlemen of the jury, the evidence is in-that is indeed racy performance from a naturally aspirated, short-deck, small-block package sipping pump fuel.
Will everyone achieve over 600 hp from building upon a Dart 363ci short-block? Nope. As always, a lot will depend on your chosen heads, cam, and other supporting hardware, and those choices-especially the bumpstick-will be primarily guided by your project's desired rpm band. But Dart's 363 seems to have the guts to handle whatever you or your engine builder might throw at it.
Will everyone achieve over 600 hp from building upon a Dart 363ci short-block?
Finished to a 4.125 bore in...
Finished to a 4.125 bore in the 363, Dart’s short-deck Special High Performance block can handle up to 4.185 inches, in case you ever need to rebuild. Like all Dart blocks (and heads, for that matter), it’s cast and precision-machined in the USA, and you can see that this 165-pound thug makes a production 302 casting look utterly frail by comparison. The block valley is machined to accept factory roller-lifter dog-bones and spider—not that we’ll be using them this time. Each 363 short-block is hand-assembled by Dart’s highly experienced builders.
Bottom-end rigidity equals...
Bottom-end rigidity equals engine longevity. Dart’s SHP block bulkheads are massive, as are the four-bolt (on the two, three, and four) main caps. The center bolts are 1/2-13x3.250, while the splayed outer pair are 7⁄16-14 x 2.750.
Particularly important with...
Particularly important with a stroker crank, the SHP bore castings extend deep in order to laterally support the piston through its full downward travel. Also note the notch for rod-bolt clearance. The bottom line is these blocks were specifically engineered for stroker cranks.