400ci Dart Aluminum Small Block Engine Build - Aluma-Mouse

This All-Aluminum Small-Block Demonstrates That Light Makes Might

Bill McGuire Apr 1, 2010 0 Comment(s)

All-aluminum small-blocks have mystique. Even today, when production V-8s come with aluminum blocks straight from the showroom, there is still something magical about an all-alloy Gen I Mouse motor. Back in the '60s they were the acme of high technology, the signifiers of high-level factory connections, generally found only in exotic racers like Jim Hall's Chaparrals and Mickey Thompson's Indy cars. Here in the 21st century, aluminum small-blocks, now available to one and all straight off the rack, continue to dominate in venues where good power and light weight are key-sprint cars, to name one example.

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All this is exactly what famed Detroit race car fabricator Ron Fournier was thinking when he went shopping for a new engine for his personal, handbuilt track roadster. Fournier designed his 1,600-pound bomb as a tribute to the great track roadsters of the '50s, and also as a sort of street-legal sprint car-he likes to hot-lap the roadster at local dirt tracks when he gets the chance. An all-aluminum small-block was the perfect choice for his rod, so he called his buddies at Dart Machinery in nearby Troy, Michigan, leading purveyors of aluminum Chevy blocks. The build for Fournier's engine was performed in-house at Dart's engine shop by Jeff Lake and Tony McAfee, the company's Pro Stock specialists.

Though the piece is cast in aluminum rather than iron, the Dart block bears some dimensional similarities to the Chevy-based Olds Rocket block originally marketed by GM Performance Parts. So while the Dart casting is somewhat non-standard compared to a conventional SBC, parts channels are still comfortably wide. To accommodate big stroker cranks, the oil pain rails have been spread outboard 0.400-inch on each side, while the camshaft is raised 0.391-inch in the block, rolling on big-block Chevy journals. Thus configured, the casting can accept bores of up to 4.185 inches and strokes of up to 4.125 inches, for as much as 454 ci. While Dart's block is most typically used in oval racing, the casting was designed from the start to support street hardware, including a mechanical fuel pump, a conventional distributor, and a wet-sump oil system. There are a few wrinkles involved in setting up the Dart block for road use, however, and we'll cover them here.

Fournier's roadster may be a dirt sprinter in spirit, but for the engine buildup Lake and McAfee deliberately went 180 degrees from the typical high-revving, no-flywheel, light-switch combination employed in the circle-track world. Instead, they opted for real-world street performance, with good driveability and a big, fat torque curve. Sidestepping the more expensive and exotic reciprocating components, they set the displacement at 400 ci with a 4.125-inch bore and a 3.75-inch stroke. Since that's still on the biggish side for a small-block, their cylinder head choice for this engine may raise an eyebrow or two in some quarters: the Pro1 Platinum series with 180cc intake ports, the smallest offered by Dart.

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Among his other duties at Dart, McAfee heads the company's advanced wet-flow bench research program, where he has developed some firm convictions about what works and what doesn't for a given combination. "This is the smallest port we offer and I would say it's way underestimated," he says. "The 180 has the best overall performance for the street and it's absolutely ideal for hydraulic roller cams. For power peaks below around 6,400 rpm and displacements up to 400 inches, this is the head you want." To finish off the conservative, high-velocity airflow combination, a 650-cfm Demon carburetor and a dual-plane Dart intake manifold were selected.




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