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4.5" Bore Space Iron Chevy Small Blocks

Part Number 3152
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4.5" Bore Space Iron Chevy Small Blocks
4.5' Bore Space Iron Chevy Small Blocks
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Retail Price:  $3,406.30
Your Savings:  $170.31
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4.5" Bore Space Iron Chevy Small Blocks

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.


  • 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 Service:
Cobra Power is a state of the art machine shop. For an additional $430 we will fully prep your block the right way. This will include:

  • Honing the cylinders on our Sunnen CV616 with torque plates.
  • Square decking the block.
  • Check all lifter bores and hone if necessary.
  • Check line hone, adjust if necessary.
  • Install cam bearings, freeze plugs, hard & soft plugs
  • Wash block thoroughly.

We ship all of our engine blocks through Unishippers, We will only ship to commercial locations with loading docks and or forklift trucks. If this is not an option we can also set the freight for customer pick up at the shippers terminal. Call 305-893-5018 for an accurate shipping price.

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