BIG BLOCK CHEVY 612 620 632 638 Short Block

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Looking for Professional quality and Reliable Performance? CNC-Motorsports will give you just that!

Here at CNC-Motorsports our short blocks start with new Dart Tall Deck Big M sportsman block. We start by seasoning the new Dart block, we run each block threw 7 to 10 heat cycles before we do any machine work. New blocks have a tendency to change .001 to .002 thousands after the heat cycles are complete. All blocks are checked and then line honed if needed to get a baseline for all of the BHJ blueprinting fixtures. From this point we square up the decks using BHJ’s Blok-Tru to get the desired deck heights. Once this is done we bore the block using BHJ’s Bore-Tru to get the desired spacing.

The next step is the honing process. We install main caps and torque plates to ensure cylinder bores ends up as true to actual running conditions as possible. In our honing process we aim for around 30º crosshatch to achieve the most compression while still allowing the rings to travel. Bores are measured with plates still attached and recorded on the blue print sheet.



Once all the machine work is completed, the block is washed and prepped for assembly. During the assembly process, all components are measured and corrected to obtain correct clearances. All of these measurements are recorded on the blueprint sheet.



Rotating assemblies in these short blocks are all weight matched within +/-2 grams, and the crankshaft is balanced with in ½ of a gram.

Here at CNC Motorsports we strive for excellence in our craftsmanship to provide our customers with the best possible product money can buy



Big Block Chevy Short Block Assembly



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New Eagle 4340 forged steel crankshaft
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New Scat/Eagle H-Beam connecting rods ( Bushed Fit Pins )
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New JE forged high performance aluminum pistons, with pins and locks
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High performance plasma moly piston ring set

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ACL/Clevite 77 Rod & Main Bearings
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Dura Bond Cam Bearings
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Dura Bond Finishing Kit
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Freeze Plugs
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Victor Reinze Rear Main Seal
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New Dart Big M Sportsman Tall Deck Block – Has 3 Centered 4 Bolt Splayed Caps

Total Seal Gapless Top Rings (add $ 170.00)
TriArmor Coated Bearings (add $ 140.00)
ARP 2000/L19 Rod Bolt Upgrade (add $ 90.00)
Dart Big M Competition Block (add $ 425.00)