Forged Small Block Chevy Rotating Assembly, 421 Flat Top, 350 Mains, 6 Rod

Speedway introduces forged rotating assemblies, with an optional balance job. Includes new 2-pc rear main seal crank, rods and pistons. Cranks are new so they use standard size bearings.

All Scat 4340 cranks are 2-piece rear main seal, internally balanced and weigh approximately 51-55 lbs.  All balancing is done with our state-of-the-art Hines balancer by race mechanics with over 30 years of experience!  A kit purchased with the optional balance job will ship in 24-48 hours (must be purchased separately, part # 91510200). These rotating assembly engine rebuild kits may require additional charges for heavy metal.

If you are going to run this crank in a sprint car motor, you must have the crank flange turned down prior to balancing the crank to allow it to go through the motor plate. 

NOTE: A balance rotating assembly option is currently not offered for this package but the proper balancing service can be determined after your order is placed.  If you would like our balancing option service for 395 and 421 engine builds, contact customer service.

NOTE: Piston rings are not included and must be purchased separately. Use Style C rings.

50 cc 14.0:1 compression ratio

Kits feature:

• Scat 4340 Forged Steel Crankshaft
  • Standard size journals
  • Straight shot and chamfered oil holes
  • Nitride hardened and shot peened
  • Lightening holes in all rod throws
  • Large radius on all journals
• KB Signature Series Forged Pistons
  • 2618 aluminum alloy construction
  • T-6 heat treated
  • 4.000 " bore pistons available in standard, .030, .040, or .060 sizes
  • 4.125 " bore pistons available in .030 or .040 sizes
• Speedway 4340 H-beam Connecting Rods
  • Full floating pin in silicon bronze bushing
  • Precision bolt bushings to positively locate cap
  • 6.0 " lengths
  • 634 grams
  • Weight matched set of 8 rods
• King HP Series Main and Rod Bearings
  
  • 0.015 " thick top layer for superior macro particle embedability and conformability
  • 40 Vickers hardness to resist overlay migration and extrusion
  • 450°F heat threshold for superior protection against friction and overheating
  • Mains are 3/4 grooved for improved oiling to the rod journals
  • Bi-metal aluminum silicon alloy featuring fine micro-bore finish

Kits feature:

• Scat 4340 Forged Steel Crankshaft
  • Standard size journals
  • Straight shot and chamfered oil holes
  • Nitride hardened and shot peened
  • Lightening holes in all rod throws
  • Large radius on all journals
• KB Signature Series Forged Pistons
  • 2618 aluminum alloy construction
  • T-6 heat treated
  • 4.000 " bore pistons available in standard, .030, .040, or .060 sizes
  • 4.125 " bore pistons available in .030 or .040 sizes
• Speedway 4340 H-beam Connecting Rods
  • Full floating pin in silicon bronze bushing
  • Precision bolt bushings to positively locate cap
  • 6.0 " lengths
  • 634 grams
  • Weight matched set of 8 rods
• King HP Series Main and Rod Bearings
  
  • 0.015 " thick top layer for superior macro particle embedability and conformability
  • 40 Vickers hardness to resist overlay migration and extrusion
  • 450°F heat threshold for superior protection against friction and overheating
  • Mains are 3/4 grooved for improved oiling to the rod journals
  • Bi-metal aluminum silicon alloy featuring fine micro-bore finish

• 415/421-ci SBC (3.875-inch stroke)
  • Displacement: 421 ci
  • Bore x Stroke: 4.155 x 3.875 inches
  • Compression: 10.7:1
  • Rod: 6.00-inch