Dart Big M Cast Iron Block

DART Big "M" Cast Iron Block
BB Chevy
Dart has reinvented the Rat motor!
The lubrication system has been re-designed to create a true "priority main" system that oils all the main bearings before the lifters for extra reliability. The stepped main oil gallery (9/16" to 1/2" to 7/16") increases the flow of oil to the crank at high rpm, while the front oil crossover eliminates internal oil leaks around the distributor shaft. The result: more oil at the bearings and pushrods where it's needed, and less power-robbing crankcase windage.
Big-blocks are prone to head gasket failure in the long spans between head bolts.
DART has added two head stud bosses on both sides of the lifter valley to take the place of the "missing" head bolts. The bosses are slotted so you can use studs instead of the hard-to-install bolts.

The Big "M" is engineered to be the strongest, most reliable, and easiest to build big-block on the market. It's time to step up to the Big M!

Dart Big M Block Features:
Siamesed extra-thick cylinder walls resist cracking and improve ring seal (minimum .300" thick with 4.625" bore).
Scalloped outer water jacket walls improve coolant flow around the cylinder barrels to equalize temperatures.
Standard 9.800" and extra-tall 10.200" deck heights available for stroker engines.
Four-bolt main bearing caps in steel or ductile iron have splayed outer bolts for extra strength.
Crankshaft tunnel has clearance for a 4.500" stroke crank with steel rods without grinding.
True "priority main" oil system lubricates the main bearings before the lifters.
Oil filter pad is drilled and tapped for an external oil pump.
Rear four-bolt cap uses standard oil pump and two-piece seal - NO adapter required
Lifter valley head stud bosses prevent blown head gaskets between head bolts.
External block machining reduces weight without sacrificing strength.
Mechanical fuel pump boss, clutch linkage mounts, and side and front motor mounts simplify installation in any chassis
Dual oil pan bolt patterns fit standard and notched oil pans.
Bellhousing flange and rear main bearing are reinforced with ribs to resist cracks

Big "M" Block Specifications:
Material: Superior Iron Alloy
Block Height: 9.800" & 10.200"
Bore: 4.250" or 4.500" unfinished
Bore & Stroke: 4.625" x 4.750" max recommended
Main Bearing Size: Std. BBC
Main Caps: All 4-Bolt Steel or Ductile Iron
Weight: 240lb.
Largest Recommended Bore: 4.625"
Camshaft Bearing Diameter: Std. BBC
Camshaft Position: Std. BBC
Cam Drive: Std Timing chain, gear drive, or belt drive
Cylinder Wall Thickness (min): .300" @ 4.625" Bore
Deck Thickness (min): Adequate for all apps
Torque Specs/Main Caps: 1 - 5 1/2" bolts/2 - 4 1/2" splayed
Cubic Inch: 632" max recommended
Fuel Pump: Mechanical Fuel Pump provision
Freeze Plugs: Press-in cup plugs
Oil Filter: Std. oil filter location
Rear Main Seal: Std. 2-piece seal

Part #	Description	Price/Each
31263344	Steel Main Caps - 9.800" Deck - Std. Main - 4.250" Bore	$2475
31263354	Steel Main Caps - 10.200" Deck - Std. Main - 4.250" Bore	$2475
31263444	Steel Main Caps - 9.800" Deck - Std. Main - 4.500" Bore	$2575
31263454	Steel Main Caps - 10.200" Deck - Std. Main - 4.500" Bore	$2575
31263644	Steel Main Caps - 9.800" Deck - Std. Main - 4.600" Bore	$2575
31263654	Steel Main Caps - 10.200" Deck - Std. Main - 4.600" Bore	$2750
31273344	Ductile Main Caps - 9.800" Deck - Std. Main - 4.250" Bore	$2075*
31273354	Ductile Main Caps - 10.200" Deck - Std. Main - 4.250" Bore	$2075*
31273444	Ductile Main Caps - 9.800" Deck - Std. Main - 4.500" Bore	$2149*
31273454	Ductile Main Caps - 10.200" Deck - Std. Main - 4.500" Bore	$2149*
31273644	Ductile Main Caps - 9.800" Deck - Std. Main - 4.600" Bore	$2149*
31273654	Ductile Main Caps - 10.200" Deck - Std. Main - 4.600" Bore	$2149*