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The SP53NB covers the same ground as ATK's other new 377 short block, minus the dish: flat-top forged pistons here push static compression well above what the dished-piston version offers, for someone finishing a stroker build around their own heads rather than buying a full long block.
Dropping the piston dish raises compression for any given chamber size, which suits a buyer chasing more static compression on pump gas or race fuel without changing heads. Everything above the deck, heads, intake, carburetor, distributor, valve covers, is still left for the installer to choose.
ARP-bolted forged H-beam rods ride on a forged Scat 4340 crankshaft, both finished to work with the 5cc flat-top pistons at the top of each cylinder. Bore and stroke measure 4.000 and 3.750 inches for the 377 cubic inches of displacement. ATK installs and seals the Dura-Bond cam bearings and brass freeze plugs at the factory, and the rotating assembly is externally balanced with a 168-tooth flexplate or flywheel ring to suit the Scat kit.
Q: How much compression will I actually get? Expect somewhere around 10.3:1 to 11.9:1, depending on the chamber volume of the heads you choose to run.
Builders chasing more static compression on pump gas or race fuel are the obvious audience for this version over the dished-piston alternative.
Full terms: 30-day startup warranty · returns
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