Aftermarket Block Buyer's Guide

Dart Machinery Big MDart's Big M big-block is a no-compromises design that reinvents the Rat motor. The oiling passages feature a true priority main system that lubricates all of the main bearings before oiling the lifters. The stepped main oil gallery increases the flow of oil at high rpm, and the front oil crossover eliminates oil leaks around the distributor shaft. And unlike factory big-blocks, head-gasket failures have been greatly reduced with the addition of two head-stud bosses on both sides of the lifter valley to provide extra clamping force.

PN: Call for specific applicationBlock material: Cast-iron alloyDeck height: Available with 9.800- or 10.200-inch deckBearing-cap type: Steel four-boltMain-journal diameter: 2.937 inchesOil system: Wet or dry sumpCylinder-bore range: 4.250 to 4.625 inchesMaximum stroke: 4.750 inchesMaximum displacement: 632 ci (10.200-inch deck)Weight: Starts at 262 pounds with a 4.250-inch borePrice: $2,485

World Products Merlin IIIThe Merlin III big-block is a seriously stout piece that can withstand up to 2,000 hp. The block has much thicker decks, beefier cylinder walls, nodular-iron caps with splayed bolts, and can easily accommodate up to 638 ci. While it's a pricier initial investment, the block holds no surprises, comes fully machined, and is compatible with any off-the-shelf Chevy components.

PN: Call for specific applicationsBlock material: High-density cast ironDeck height: Available with 9.800- or 10.200-inch deckBearing-cap type: Nodular-iron four-boltMain-journal diameter: Standard ChevroletOil system: Wet or dryCylinder-bore range: 4.250 to 4.625 inchesMaximum stroke: 4.750 inchesMaximum displacement: 638 ci (10.200-inch deck)Weight: 270 poundsPrice: $2,049

GM Performance Parts SBC Bow TieGM Performance Parts' siamese-bore Bow Tie small-block can be stroked up to 447 ci with a 4.155-inch bore and 4.125-inch stroke, while retaining a minimum 0.275-inch wall thickness. All blocks are precision CNC-machined and do not require additional blueprinting for correct production tolerances.

PN: 10185047Block material: Cast ironDeck height: 9.025 inchesBearing-cap type: Steel iron four-bolt on center three main capsMain journal diameter: 2.45 inchesOil system: Wet sumpCylinder-bore range: 4.000 to 4.155 inchesMaximum stroke: 4.125 inchesMaximum displacement: 447 ciWeight: 200 poundsPrice: $2,336.31

Dart Machinery Dart Little MDart's Little M block comes fully machined and ready to be assembled with any off-the-shelf small-block components. It features extra-thick cylinder walls, four-bolt main caps with the choice of nodular-iron or billet-steel caps, and you get the choice of using either standard 350 or 400 main bearings.

PN: Call for specific applicationBlock material: Cast-iron alloyDeck height: Available with 9.020- or 9.325-inch deckBearing-cap type: Steel four-bolt for center three main capsMain-journal diameter: 2.450 inches (standard Chevrolet 350) or 2.650 inches (400 style)Oil system: Wet or dryCylinder-bore range: 4.000 to 4.185 inchesMaximum stroke: 4.125 inchesMaximum displacement: 454 ciWeight: 185 poundsPrice: $2,184

Ford Racing Performance Parts FRPP R302The original aftermarket A4302 four-bolt block has been offered by Ford since the '90s. The rugged block now features a siamesed cylinder bore, standard 302ci 2.249-inch main journals, and nodular iron caps, and it can be bored and stroked to 360 ci. It's important to note that the block is shipped with semi-finished lifter and main bearing bores, which will set you back an additional $500 to $700 worth of machining before assembly can begin.

PN: M-6010-R302Block material: Cast ironDeck height: 8.200 inchesBearing-cap type: Steel four-bolt on Nos. 2, 3, and 4 mainMain-journal diameter: 2.249 inches (standard 302 diameter)Oil system: Wet or dry sumpCylinder-bore range: 4.00 to 4.125 inchesMaximum stroke: 3.400 inchesMaximum displacement: 360 ciWeight: 160 poundsPrice: $1,695