Cast Iron S/B Chev Engine Block, 4.125" Bore 9.025" Deck Height 400 Mains 4 Bolt

Cast Iron S/B Chev Engine Block, 4.125" Bore, 9.025" Deck Height, 400 Mains, 4 Bolt

Elevate your small-block Chevy build with a robust, semi-finished foundation designed for serious street and performance use. Cast from premium Class 32B iron, this block delivers exceptional strength while minimizing machining. Its Siamese cylinder bores, splayed billet steel four-bolt main caps, and a priority main oiling pathway work together to keep bearings fed under demanding conditions. Built to seal reliably with standard off-the-shelf components, it’s the ideal starting point for a high-performance street build.

Key features

• Siamese cylinder bore design for compact, race-ready blocks
• Billet steel, four-bolt main caps with a splayed design for added hold-down strength
• Main Priority Oiling system (can be paired with dry sump) for dependable oiling under load
• Thick deck height enhances head gasket sealing and accommodates common, off-the-shelf components
• Compatibility with standard camshafts, timing chains/gears, and oiling systems to minimize bespoke machining
• Premium cast iron (Class 32B) and name-brand engineering designed for street and performance builds
• Finish-machining required by qualified machinists; factory tolerances apply and may be adjusted for your components

Specifications

• Bore: 4.125 in (max bore: 4.185 in)
• Stroke: 4.000 in
• Deck height: 9.025 in; Deck thickness: 0.675 in
• Cylinder wall thickness: 0.275 in (min at 4.185 in bore)
• Cam journal OD: 1.869 in (STD)
• Cam plug: 2.375 in press-in cup
• Lifter bores: 0.842 in
• Main bearing size: 2.650 in (400); Main bearing bore: 2.849 in (400)
• Main caps: Billet steel, 3 center caps; 4-bolt splayed design
• Main cap bolts: 7/16 in & 3/8 in on Caps 1 & 5; 7/16 in on Caps 2, 3 & 4 (splayed)
• Main cap register: Deep stepped (no dowels required)
• Oil system: Main Priority Oiling (can use dry sump)
• Oil pump shaft: 350.481 in
• Oil filter: STD; Uses 2-bolt adapter
• Oil pan: STD 350
• Rear main seal: STD 400 2-piece
• 2-piece serial number location: Left front & main caps
• Starter: STD
• Stud holes, head: Blind holes
• Timing chain/gears: STD
• Timing cover: STD
• Weight: 92 kg (205 lbs)

Why builders choose this block

• Provides a robust, semi-finished foundation that minimizes machining while delivering durability for high-performance combinations.
• The combination of Siamese bores, 4-bolt splayed main caps, and priority oiling helps maintain reliability under aggressive street performance and track usage.
• Extra-thick deck height supports dependable head gasket sealing and broad component compatibility with off-the-shelf parts.
• Designed to work with standard street components, reducing bespoke machining while still allowing precise clearance and tolerances when finished by a qualified machinist.

Machining & assembly guidance

This block is intended to be finished by a professional machinist. Expect factory tolerances that may require adjustment for your specific components. Key guidance includes:

• Deburr cam bearing OD before installation; when removing main caps, de-burr both caps and block to maintain correct bearing sizes.
• Cylinder bores may require honing and pistons may need width/skirt clearance adjustments; oversized pistons are common and require appropriate skirt clearance.
• Very few aftermarket components drop in without additional checking and machining—verify all tolerances and clearances with a qualified machinist for reliable performance.
• Ensure head gasket sealing and oiling pathways align with your chosen components; consider compatibility with a dry sump system if desired.

Applications

Ideal for serious street-performance builds where strength, oiling efficiency, and compatibility with off-the-shelf parts matter most. This block offers a solid, proven platform for modern small-block Chevy combinations, balancing rugged cast-iron durability with practical assembly considerations for reliable, long-term operation.