ATK Engines SP15NB Chevy 377 Stroker Short Block, 18cc Dish

The ATK SP15NB is a short block for a Chevy 377 stroker, built on a new American-made, 1-piece-seal block with heavy-duty 2-bolt main caps that go beyond a stock GM 2-bolt casting. Scat parts make up the rotating assembly here, a nodular-iron crank and forged I-beam rods on ARP 8740 bolts, under 18cc dished hypereutectic pistons.

Who this short block suits

Because a dished piston trims less chamber volume than a flat-top would, compression here runs lower for a given head: roughly 9.1:1 up to 10.3:1 depending on chamber size, which can vary with deck height and gasket thickness. That makes it a fit for a buyer planning a larger-chamber aluminum head or a boosted combination rather than chasing maximum static compression.

What comes with it

• The cam bearings arrive pre-installed and clocked to spec, with the freeze plugs and oil galley plugs sealed at the factory.
• No cylinder heads, camshaft, intake, oil pan, or timing cover ship with a short block; you supply the top end.
• Flexplate and flywheel use an externally balanced 168-tooth pattern matched to the Scat rotating kit.

Common questions

Does this include heads or a cam? No, a short block covers the bottom end only; heads, camshaft, and induction are yours to add.

What break-in oil should I run? ATK calls for non-synthetic 10W30 across the first 3,000 miles, filter brand left to your preference.

Is the block heavy-duty? Yes, it uses upgraded 2-bolt main caps rather than a stock GM casting. California requires BAR compliance for engine swap installations.