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 the 363, Dart’s short-deck Special High Performance block can
Bottom-end rigidity equals engine longevity. Dart’s SHP block bulkheads are massive, as ar
Particularly important with a stroker crank, the SHP bore castings extend deep in order to
On The Dyno
|w/650 Demon||w/850 Demon||Difference
From a business that literally began in a two-car garage, Dart Machinery has come a long, long way in thirty years, yet has remained loyal to its Detroit-area roots. Like many in the automotive aftermarket, Dart founder Richard Maskin is a racer and mechanical wizard who began engineering and building hardware for his own drag race programs.
Other racers soon took notice of his on-track success, the orders started piling in, and Dart Machinery evolved into a Motor City success story that now spans two huge facilities encompassing the company’s R&D, administrative, warehousing, and ultra-modern machining operations. For the enthusiast, engine blocks and cylinder heads—and now assembled short-blocks—are the primary focus, but we wouldn’t be surprised to see Dart branching out into other components and products as time goes by.
Speaking of cranks, the stroke is 3.400 inches (same as a typical 347’s), and Dart offers
Likewise, you can choose between H-beam or I-beam (Eagle 5.400-inch) steel rods when order
Desired compression will dictate your choice of flat-top or (16cc) dished pistons. Both ar
After a couple pulls, Jeff Lake verified that lash was adjusted within the cam manufacture
As with our earlier 427 project, we’re topping this 363 short-block testbed engine with Da
The heart-shaped chambers are normally whittled out to 62 cc, but since Dart does all mach
Soon the build got underway using Dart’s newly introduced high-performance assembly lube.
With high rpm on the horizon, Comp Cams (www.compcams.com) Ultra Pro Magnum roller rockers
Which brings us to the all-important choice of bumpsticks. With the idea being to get a bi
Ever seen a CNC-automated vertical line-honing mill before? Neither had we until we encoun
Flow benches are of course essential in researching, developing, and verifying cylinder he
Dart doesn’t cast its blocks or heads—these are poured to the company’s specs by a special
Tony also used Dart’s two-piece, adjustable pushrod guideplates that fit together like puz
As with the Dart 427 build, an affordable Professional Products Hurricane single-plane man
Also shared with the previous Dart 427 project are the Kooks headers with their generous p