Dart 31521322 4.5 Bore Spacing Block
4.5" Bore Spacing Aluminum Chevy Small Block
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 Darts 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.
- 8.850, 9.025, 9.075, 9.325 and 9.500 deck heights allow for
- 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
- Relocated oil pan rails are spread .400 per side (.800 wider
than stock) to increase crank/rod clearance and reduce windage
- 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
- 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 recue twisting with cam
- 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.
- Dart blocks are available fully finish prepped.