By spreading the cylinder bore centerlines from the standard 4.400” to 4.500”, large bore sizes can be achieved with adequate head gasket sealing space between the cylinders.

Bosses are added at the ends of the decks to accommodate two extra head studs, increasing clamping loads and improving gasket sealing. (The extra studs are also provided for in Dart’s new 4.500” bore space cylinder heads). These new blocks are ideal for big inch competition engines. The cam location is raised .391” and oil pan rails are spread .400” per side on both the iron and aluminum blocks, providing lots of room for stroker crankshafts while eliminating the need for fragile small base circle camshafts. Big block cam bearing journals are standard, and 350 or 400 main bearings are available.

It is recommended that you contact a Dart technical representative before placing an order for this item. Detailed information about your planned engine build will help to ensure that you choose the right configuration for your motor and that any special parts and considerations are taken into account.

Features:
- Premium alloy: Dart aluminum blocks are cast from 355-T61 aerospace alloy for superior strength and durability.

- 8.850", 9.025", 9.075", 9.325" and 9.500" deck heights allow for greater versatility.

- 4.500" bore spacing comes with 4.180" bore size standard, larger bores available on request, please call.

- Raised camshaft .391" (4.912" camshaft to crankshaft centerlines) provides more clearance for stroker cranks and eliminates need for fragile small base circle cams. Option for .434 raised cam also available.

- Relocated oil pan rails are spread .400" per side (.800" wider than stock) to increase crank/rod clearance and reduce windage losses.

- Oil pan bolt holes are relocated in line with main caps to eliminate interference with rotating assembly.

- Main bearing bores are available for 350 (2.45") and 400 (2.65") bearings allow engine builders to maximize crankshaft strength and minimize friction.

- 4 bolt billet steel main caps have splayed outer bolts minimize bearing bore distortion.

- Big block camshaft bearings allow use of cams with larger base circle diameter to improve strength and rescue twisting with cam driven pumps.

- Dual starter mounts allow starter to be mounted on either side of block for chassis and oil pan clearance.

- Front and rear external oil inlets, crossover and restrictor provisions to simplify plumbing with external pump.

- Scalloped outer water jacket walls improve coolant flow around the cylinder barrels to equalize temperatures.

- Coated cam bearings, freeze plugs and dowels are included.

Block Prep Options
Dart blocks are optionally available fully finish prepped. If you choose to order your block this way you can specify a final lifter spec and a final hone spec. Your block will be finish machined to your specs, final prepped and washed, pipe plugs and freeze plugs will be installed, then it will be bagged and boxed. Your block will arrive finished and ready to use!