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What Is the Discontinued BluePrint Engines BP3556 355 C.I.D. Small Block Chevy Engine?

The BP3556 was a BluePrint Engines 355 cubic inch Small Block Chevy crate engine built around a roller-cam compatible 350 block with a forged rotating assembly. While this engine has been discontinued, customers may still encounter BP3556 engines in older builds, restoration projects, used vehicle purchases, or when sourcing replacement components.

 What Are the Basic Specifications of the BP3556 Engine?

The BP3556 was built using a traditional Gen I Small Block Chevrolet platform and included:

  • 355 cubic inches (5.8L)
  • 4.040-inch bore
  • 3.48-inch stroke
  • 4-bolt main block
  • One-piece rear main seal
  • Roller cam compatible block
  • Passenger-side dipstick provision
  • Mechanical fuel pump provision
  • Externally balanced rotating assembly
These features made the BP3556 a durable street performance engine with an upgraded forged rotating assembly. What Rotating Assembly Was Used in the BP3556? The BP3556 utilized forged components for increased strength and reliability.

Crankshaft

  • Forged SCAT crankshaft
  • External balance rear
  • One-piece rear main seal configuration

Connecting Rods

  • SCAT 4340 forged steel connecting rods

Pistons

  • Probe forged pistons
  • 13.8cc dish design
The forged crankshaft and rod combination offered significantly greater durability than a stock cast rotating assembly. What Bore Size Does the BP3556 Use? The BP3556 was produced with:
  • 4.040-inch bore
  • 3.48-inch stroke
This combination results in 355 cubic inches of displacement. Important: Original manufacturing documentation specifies the block was intended for a .040-inch overbore only. Is the BP3556 a Roller Cam Engine? Yes. The original build specifications identify the BP3556 as being built from a roller-cam compatible Small Block Chevy block. Customers replacing camshaft components should verify the engine's current valvetrain configuration before ordering replacement parts. What Rear Main Seal Does the BP3556 Use? The BP3556 uses a:
  • One-piece rear main seal
Replacement parts should be ordered using a Small Block Chevy one-piece rear main seal application. Is the BP3556 Internally or Externally Balanced? The BP3556 uses an externally balanced rotating assembly. When replacing rotating assembly components, the following must remain compatible:
  • Harmonic balancer
  • Flexplate
  • Crankshaft balance configuration
Using mismatched balance components can cause vibration and engine damage. Can the BP3556 Use a Mechanical Fuel Pump? Yes. The original block specifications include:
  • Mechanical fuel pump mounting provisions
  • Fuel pump pushrod hole
  • Traditional Small Block Chevy fuel pump compatibility
Customers converting to EFI systems should follow the fuel system requirements of their chosen EFI manufacturer. What Information Should Be Verified Before Ordering Replacement Parts? Before ordering service parts for a discontinued BP3556 engine, verify:
  • Engine serial number
  • Block casting number
  • Bore size
  • Rear main seal configuration
  • Harmonic balancer type
  • Flexplate or flywheel balance style
  • Current camshaft and valvetrain configuration
Verifying these details helps ensure proper replacement part selection.