Butler Performance 407-413 ci Balanced Rotating Assembly Stroker Kit, for 350 Block, 4.250" str.

Our long-rod assemblies offer the ultimate in durability and performance.

Butler's balanced 407-413 ci long-rod stroker assembly for the Pontiac 350 block — a 4.250" stroke built around a true-Pontiac Ross forging and internally balanced in our shop. Nitrous-safe and ready to build a strong, dependable bottom end.

What's Included

• New Cast or Forged Crank 4.250" Stroke
• Choose Desired Bore Size and Ring Type
• Forged Flat Top Ross Pistons, Dish, or Dome Available
• Specify Desired Compression Ratio
• Aftermarket 990 wrist pins
• Bushed/Full Float H-beam 6.800" rods
• Pin Fitted
• Total Seal Classic Race Rings
• Rod Bearings selected based on proper clearance- verified by our shop
• Butler Process- Balanced Internally

Choose Your Options

• Crankshaft — Cast or Forged. New cast steel cranks are an excellent, affordable upgrade over a 30+ year-old factory crank (great for street engines without power adders). Step up to a 4340 forged crank for maximum strength and durability — cheap insurance that leaves the door open to add power later.
• Bore. We start bore options at .030" over so the block cleans up and the pistons and rings seat within spec. Larger bores are available. We recommend having the pistons in hand when the cylinders are honed to set piston-to-wall clearance off the actual parts.
• Pistons — Flat Top or Custom Dish. Butler/Ross forged pistons on our exclusive true-Pontiac "strut-style" forging — some of the lightest, strongest pistons available, and nitrous-safe. Choose a flat top or a custom dish machined to your target compression ratio.
• Compression Ratio. Tell us your heads and desired compression; our techs work with Ross to design the piston to hit it. Custom dish pistons run a 10–12 week lead time.
• Rings. Total Seal, standard on all assemblies. Classic Race (CR) plasma-moly; upgrade to AP Advanced Stainless (CS) for longer life and tighter tolerance, or Gapless Top (M) to seal cylinder pressure between the top and second rings.
• Wrist Pins. Standard Ross 5115 chromoly pins are rated to 800 hp naturally aspirated; upgrade to .220" wall bearing-steel pins for higher-horsepower and power-adder builds.
• Rods & Rod Bolts. 4340 forged H-beam or I-beam rods, full-floating and bushed. Standard ARP8740 bolts (190,000 psi); upgrade to ARP2000 (220,000 psi).

Bearings & Clearance

Bearings are included. Rod-bearing clearance is checked and verified in our shop at no charge. Main-bearing clearance depends on your crank journal size, bearing brand, and finished main-bore size — it can't be verified here because it has to be torqued into your block — but we'll gladly swap for -1 or X bearings (in new condition) if you need them. We recommend having the crank and main bearings in hand when the mains are machined.

The Butler Process — Balanced In-House

Every rotating assembly we sell, regardless of brand, is internally balanced in our shop by our own machinists. We weigh and pin-fit the rods and pistons, computer-balance the crank to the assembly, and document it all on a balance card that ships with your kit. This assembly is internally balanced and requires a neutral-balanced flexplate/flywheel and harmonic balancer.