How to Build Killer Chevy Small-Block Engines. Mike Mavrigian
block is legal for 305 Racesaver Sprint Series racing and is suitable as a stock replacement or performance upgrade block. To accommodate race classes that require stock displacements, this block features non-siamesed 3.750-inch cylinder bores and also has priority main oiling, thicker decks, blind head bolt holes, and splayed four-bolt main caps. It accepts standard SBC parts and has a rear external oil feed, crossover and restrictor provisions, an open lifter valley, and enlarged lifter bosses.
Iron Eagle 4.500 BS
The Iron Eagle is targeted at advanced engine builders for unlimited late-model or off-road truck maximum competition. The spread-bore spacing of 4.500 inches requires special 4.500-inch cylinder heads and components. The 4.500-inch bore spacing (as opposed to the standard 4.400-inch spacing) allows larger bore diameters and gasket sealing surface between bores. The maximum recommended bore size is 4.250 inches.
This block features a 0.391-inch raised cam tunnel, but an optional 0.434-inch raise is also available. Oil pan rails are spread out 0.400 inch at each side for reduced windage and added stroker clearance. Oil pan bolt holes are in line with the main caps to eliminate interference with stroker setups. Other features include big-block cam bearings, dual starter mounts to provide a choice of left or right location, front and rear external oil inlets, and crossover and restrictor provisions.
Aluminum Billet Block
In addition to the wide variety of iron and aluminum cast blocks offered by Dart, the firm also offers an aluminum billet block that is machined from one huge chunk of dense forged 6061 aerospace aluminum alloy. These full-water-jacket blocks are custom ordered to your specs in terms of bore diameter, bore centerline, standard or 4.500-inch bore spacing, the deck height of your choice, the standard or raised cam bore location, cam tunnel options up to 60 mm, and custom lifter bore diameter and location. They are equipped with either steel or optional aluminum main caps. For a block that can be custom engineered to a builder’s custom specifications, this is the trick pony.
Dart’s Iron Eagle small-block iron block is shown here. (Photo Courtesy Dart Machinery)
This is an example of a Dart billet block that is ready to ship. The builder then final-hone-sizes the cylinder bores, cuts decks to desired height, and sizes lifter bores to accommodate the lifters of choice. (Photo courtesy Dart Machinery)
Brodix
All Brodix blocks are CNC machined from A-356 high-strength virgin aluminum castings and are popular choices for drag, late-model, and sprint car racing applications. A wide variety of deck heights, bore sizes, and main cap materials is available in addition to CNC-lightening options that carve unneeded material from the blocks, effectively skeletonizing to reduce weight where possible.
Some block manufacturers, such as Dart, offer the option of billet aluminum blocks that are CNC machined starting with raw dense aluminum forged billets. Shown here are raw billets and semi-finished CNC machined blocks. (Photo Courtesy Dart Machinery)
Main bore and cylinder bore options include a 400 main/4.125-inch bore, 350 main/4.125-inch bore, 400 main/4.000-inch bore, and 350 main/4.000-inch bore.
Cam bearing choices include a small-block babbit, a big-block babbit, a standard 2.250-inch OD roller bearing or 50-mm roller bearing, and standard or +0.391-inch raised cam bearing locations. Note that the use of babbit-style cam bearings requires the use of wide cam bearings with 1/4-inch locks in the center bearing locations and spiral locks on the two end bearings. Roller cam bearings require spiral locks on all five bearings.
A host of custom-order versions of blocks are offered, including those with either wet or dry sump applications, with or without the fuel pump boss, standard or wide-pan rails, side water reverse cooling, front oil scavenging, lifter bore locations, spark plug holes, 350 or 400 mains, standard light steel or titanium main caps, deck heights of 9.000 to 9.300 inches, 9.000 to 9.500 inches, and 9.020 inches.
Stroker clearance is provided for 4.125-inch crank strokes if the block has a standard cam location. For raised-cam blocks, clearance is already set for a 4.250-inch stroke. The 410 sprint car blocks are clearanced for a 3.800-inch stroke.
Note: As shipped, cylinder sleeves are left slightly above the deck intentionally, allowing the builder the choice of surfacing the sleeves flat with the deck or not. As you can see, Brodix blocks are intended for serious pro-level racing applications with a multitude of options available to suit specific build requirements.
Brodix blocks are cast aluminum and intended for racing applications. Standard platforms are weight relieved via CNC cutouts, but additional weight relief is available as an option. (Photo Courtesy Brodix)
An example of optional block side lightening is shown where material has been removed without compromising block strength. (Photo Courtesy Brodix)
Brodix offers specific head stud kits for their blocks based on the builder’s choice of specific Brodix cylinder heads.
Note that block versions are also available in solid form with no water jackets for extreme drag applications.
Basic order part numbers for blocks, not including the many options mentioned earlier, are as follows:
400 main/400 bore……………8011000
350 main/350 bore……………8011001
Donovan
All Donovan blocks are made from high-strength aluminum castings with incredibly intensive and intricate CNC milling and feature priority-main oiling. Each block is custom made to suit the engine builder’s requirements. All blocks include a head stud kit, core plugs and dowels, ductile iron sleeves, main caps, and main cap studs, washers, and nuts. When first examining a Donovan block, it seems as if it was milled from a chunk of billet aluminum. The entire block (decks, lifter valleys, sides, front, main webs, etc.) is precision milled on CNC stations with the exception of the rear face, which is the only area that gives a hint that the block began as a casting. These are serious blocks intended for racing only (sans fuel pump and filter bosses, lightened exterior sides, etc.). All holes are threaded to accept –AN straight thread O-ring fittings.
Note the as-cast block side. Although weight is reduced, blocks can be ordered with additional material removal for further lightening. (Photo Courtesy Brodix)
Aftermarket racing blocks typically feature added material at the lifter bore bosses to allow the builder to enlarge the bores to accommodate the lifter diameter of choice. When using roller lifters, lifters must stay in plane with the cam lobes and cannot be allowed to rotate, requiring either individual lifters guided in plane with dog bone guides or lifters that are paired together with a link bar. Note that this block features tapped holes between lifter bores, allowing the option of using individual or link-bar roller lifters. (Photo Courtesy Brodix)
Three basic configurations are available, including the HC400, 410, and 350/400.
HC400 Block
The basic features of the HC400 block include a weight of 105 pounds, the cam tunnel raised 0.390 inch, the deck height available to 9.500 inches, the pan rail 1/2-inch wider