Dart 427w Engine Build - Brawn Dart
Ring-end gap is critical for...
Ring-end gap is critical for proper combustion sealing, so be sure to tell Dart's order desk if you are planning, say, nitrous or boost, which would dictate a wider gap than a purely naturally aspirated application.
A shot of an installed piston...
A shot of an installed piston at bottom dead center shows how little of the skirt extends beneath the Dart block's cylinder-wall casting. Such full-length lateral support for the piston is critically important on long-stroke combinations.
Should you or your engine...
Should you or your engine builder order Dart's 427 short-block assembly, it will arrive looking something like this. Dart will optionally paint the block on request. Note that a cam is not included, as that choice should be specific to your intended application.
For our buildup and dyno testing,...
For our buildup and dyno testing, Dart's crew decided to go relatively mild and street-friendly with a Comp Cams (www.compcams.com) hydraulic-roller bumpstick having gross valve lift of 0.585/0.580 inches, and a duration of 0.050 at 242/248 degrees. Lobe separation is 110 degrees, and it was installed straight up. Displacement has a calming effect on camshafts, so this piece is way tamer ministering to 427 cubes than it would be conducting a 351.
Dart's SHP block is fully...
Dart's SHP block is fully machined to accept roller lifters and their associated hardware, so a full OEM setup was installed, as shown here.
Dart is perhaps best known...
Dart is perhaps best known for its free-flowing cylinder heads, and we went with its top-dog Pro1 CNC model with 225cc intake ports because ... well, just because we could. As made obvious by their designation, these virgin 355-T61 aluminum alloy castings are CNC-ported, flow like fire hoses, and probably didn't even break a sweat on our fairly mild combo.
Normally 62cc on the Pro1...
Normally 62cc on the Pro1 or Pro1 CNC heads, Dart machined the heart-shaped chambers on our test set to 65cc, which, when teamed with the short-block's flat-top pistons, provided a pump gas-civilized 10.5:1 compression.
Compared to factory heads,...
Compared to factory heads, the Pro1 lineup has large raised exhaust ports with a spread bolt pattern (3-inch centers). This is to allow for large primary headers and correct the restricted port shape of the stock-style 351 castings.
New from Dart are these two-piece,...
New from Dart are these two-piece, adjustable pushrod guideplates, which Tony and Jeff put to good use...
...mounting a set of Comp...
...mounting a set of Comp Cams High Energy die-cast 1.6:1 aluminum rocker arms--nothing exotic, and certainly matching the overall street/strip personality of our test engine combo.
Likewise there's nothing particularly...
Likewise there's nothing particularly exotic about the intake that was on hand for our dyno mule, though the Professional Products Hurricane is of single-plane configuration and favors revs above the 3,500-rpm mark.
Dart had a variety of "dyno...
Dart had a variety of "dyno carbs" on hand, and we decided to start testing with this 650-cfm Demon. It did well but was ultimately replaced with its 850-cfm bigger brother. Check out our dyno sidebar to see how it all did.
With efficiency that stems from years of experience, Tony McAfee and Jeff Lake had our street-friendly 427 test mule strapped down and hooked up in the dyno cell in short order, plumbing it with a set of Kooks long-tubes with primaries large enough to take advantage of the heads' cavernous exhaust ports. To be honest, little time was spent "perfecting" the combo--it wasn't necessary.
We started with a 650-cfm Demon carb, made two or three pulls while experimenting with ignition timing (the combo seemed to prefer about 31 degrees total timing), then bolted on an 850 Demon for a couple final pulls. As you can see, the result is oodles of torque and better than 1.4 peak horsepower per cubic inch. This is excellent performance from a naturally aspirated bullet with pump gas-friendly 10.5:1 compression and civilized cam specs. Equally important, however, is the longevity that can be expected from the high-quality components and fastidious assembly of the Dart 427 short-block.
|w/650 Demon||w/850 Demon|