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Dart Machinery's Little M Sportman Chevy Small-Block - Quick Tech
From the October, 2010 issue of Car Craft
By John McGann
Photography by John McGann
Ccrp 1010 Dart Machinerys Little M Sportman Chevy Small Block Engine
Dart's Little M Sportsman
Dart Machinery was founded in a backyard garage nearly 30 years ago by Richard Maskin. The company makes aftermarket engine blocks at a variety of price points for small and big Chevrolets and Fords. We have access to one of its Little M Sportsman Chevy small-blocks and thought we'd take the opportunity to compare it side-by-side with a production Chevy small-block at JMS Racing Engines in El Monte, California.
A. Siamesed Bores
That's JMS' block machinist Sal Alcaraz shining his flashlight down the water jacket of the production Chevy block. Look into the core plug opening-see the sliver of light between the cylinders? This block is nonsiamesed: The barrels of the cylinders do not touch. All production small-blocks except for the relatively rare 400s are cast this way. The Dart block has siamesed cylinders-they touch each other in a row at the 3 o'clock and 9 o'clock positions. This makes the cylinders very rigid, which results in a better ring seal.
B. Deck Thickness
The Dart block has a deck thickness of 0.675 inch. With a production block, you'd be lucky to find one with a 0.400-inch-thick deck. You get a better head gasket seal, perfect for high-compression or power-adder applications. All the cylinder head bolts in the Dart block are blind-they don't open into the water jackets like a production block. This prevents any chance of coolant from seeping up the head bolts and eventually creeping into the cylinders.
C. Cylinders
You can get a Dart Little M Sportsman block in either 4.00- (350) or 4.125-inch (400) bore sizes. However, you can bore the Dart blocks out to a maximum 4.185 inches. That's bigger than you could ever dare go with a production block. The deck height is 9.025 inches-the same as a production, as are nearly all the other dimensions of this Little M. You have a choice of either standard 350 main bearing journal sizes, which are 2.450 inches, or the slightly bigger journals of a 400 at 2.650 inches. The rear main seal for all Little M Sportsman blocks is the early two-piece design.
D. Crankcase Clearance
A production 400 engine came with a 3.75-inch stroke, and that crankshaft is what guys use to build 383s out of a 350 block. The maximum stroke Dart recommends is 3.875 inches. Combine that with a maximum 4.185-inch bore, and you will have a 426.4ci engine. Better call it a 427, though.
E. Main Caps
Most small-blocks came with two-bolt main caps from the factory. You don't need a lot of clamping force in a 175hp Malibu engine. The Little M also has four-bolt main caps, but notice that the outer bolts are situated at an angle rather than straight like the production caps. This splayed bolt design is superior because it spreads the clamp load over a much wider surface than the straight cap design. The caps themselves are made with ductile iron rather than the cast-iron alloy used at the factory. It is stronger and less resistant to fatigue and cracking than the factory material.
Oiling
One of the biggest improvements over a stock block is Dart's oiling system. Dart's block deviates from the production block by sending filtered oil from the pump to the main bearings first. After building pressure at the mains, oil goes to the cam bearings and lifters, then on to the cylinder heads through the pushrods. This priority main oiling system differs from a production block that sends oil to the cam bearings first before the main bearings. Priority main oiling is better because the crankshaft is subjected to much greater forces than a camshaft. There are additional bosses cast into the lifter valley that can be drilled for a dry-sump scavenging.
Which One to Buy?
Dart's tech guys told us sales are split right down the middle for 4.00- or 4.185-inch blocks. Since the price for either bore size is the same, we wondered why anyone would buy a 4.00-inch-bore block when the 4.125-inch block costs the same. Some racing classes limit bore size to 4.00 inches, some guys have a bad block but good 4-inch internals, and some guys just want a 4.00-inch-bore block to build a 327 or 350 to match the badges on their fenders. Otherwise, buy the 4.125-inch Little M Sportsman and build yourself a big small-block.
