Chevy 502 HO - Big CI Displacement!

GM performance Parts started with the 454 Chevy crate engine that runs very well and revved it up to a 502 cubic inch powerhouse. This GMPP 502 HO big block crate motor delivers the goods with low-end torque and top-end horsepower.

The 502 HO bottom end has the strong cast iron four-bolt block, forged steel crankshaft, forged steel connecting rods that have been shot-peened for durability and forged pistons. A high-lift roller camshaft controls the airflow through legendary rectangular-port cast iron cylinder heads. This combination provides more than enough air to fill all 502 cubic inches! Another selling feature is that the final compression ratio comes in at 8.75:1 allowing your performance GM car to make tremendous power from just pump gas.

GM Performance provides an aluminum dual-plane intake manifold, 6-quart oil pan (with windage tray), damper, cast iron water pump and a 14" flexplate. You add your carburetor, starter, and ignition system.


  • Add a stroked big block motor
  • Get low 11-second bracket racing
  • Heavy metal thunder!

*Applications have not been validated. They are merely suggestions of how you might enjoy your GM Performance Parts crate engine. Some applications may affect engine warranty. See specific warranty information. Some applications may not be emission legal; check state and local ordinances.

Part Number: 12568778
Engine type: Chevy big-block V-8
Displacement (cu in): 502
Bore x stroke (in): 4.47 x 4.00
Block (P/N 10237292): Cast iron with 4-bolt main caps
Crankshaft (P/N 10183723): Forged steel
Connecting rods (P/N 10198922): Forged steel, shot peened
Pistons (P/N 12533507): Forged aluminum
Camshaft type (P/N 24502611): Hydraulic roller
Camshaft lift (in): .510 intake / .540 exhaust
Camshaft duration (@.050 in):211'c1 intake / 230'c1 exhaust
Cylinder heads (P/N 12562920): Iron rectangular port; 118cc chambers
Valve size (in): 2.19 intake / 1.88 exhaust
Compression ratio: 8.75:1
Rocker arms (P/N 12523976): Stamped steel
Rocker arm ratio: 1.7:1
Water pump (P/N 12484890): Cast iron, long-style
Flexplate (P/N 10185034): 14"
Recommended fuel: 92 octane
Ignition timing: 36'c1 total @ 3600 rpm, with vacuum advance disconnected
Maximum rpm: 5500

502 HO engine

Part #:12568778

502 HO Dyno

Installation Notes

  • NOTE: Distributor with melonized steel gear MUST be used with long blocks and partial engines with steel camshafts, or engine damage will occur. GMPP distributor P/N 93440806 is recommended.
  • Requires addition of carburetor, fuel pump, starter, distributor and ignition system.
  • Clutch linkage boss is cast into block, but must be drilled and tapped. When using cast iron exhaust manifolds, lower head bolts may need to be replaced with bolts with shorter heads, for clearance.
  • Requires electric fuel pump because the Gen VI block has no mechanical fuel pump boss.
  • Comes with a 14" automatic transmission flexplate; use flywheel P/N 14096987 and 11" clutch assembly for manual transmission.
  • Intended for pre-1977 street vehicles or all off-road vehicles.
  • Not intended for marine applications.