Ford Racing M6010-BOSS351BB Boss 351 Big Bore Engine Block 9.5 In. Deck Height

The Ford Racing M-6010-BOSS351BB Boss 351 Big Bore Engine Block is the ultimate foundation for a high-displacement small-block Windsor build. Engineered using the latest racing and production technologies, this bare block is designed as a modern replacement for the legendary Boss 302 and Boss 351 blocks, capable of supporting displacements up to 460 cubic inches.

Cast from diesel-grade iron with Siamese bores and thick cylinder walls, this block delivers strength far beyond any Ford OEM production block. The Big Bore version (M-6010-BOSS351BB) differs from the standard 9.5" deck block (M-6010-BOSS35195) by deleting the coolant crossover holes between cylinders, allowing for a larger finished bore size and maximizing your cubic inch potential. To ensure precise bore location and concentricity, the Big Bore blocks are machined an additional .125" during the initial block fixturing and boring stage. All Ford Racing Boss blocks are cast and machined to the highest industry standards in the USA.

Key Specifications:

• Rough bore: Finished at 4.120"
• Maximum bore capacity: 4.125" (minimum bore wall thickness .180" @ 4.125" — sonic check recommended for bores greater than 4.125")
• Deck height: 9.5", finished at 9.500" + .010" to .015"
• Maximum recommended stroke: 4.250" (clearance dependent on crankshaft/connecting rod manufacturer)
• Main journal diameter: 2.749" (stock 351C size)
• Splayed 4-bolt mains on caps 2, 3, and 4
• 2-bolt mains on caps 1 and 5
• Main bearing bores finished to low limit
• Finished lifter bores; machined to accept factory roller lifter guides and retainer
• Revised oiling and cooling system passageways
• Increased bulkhead material for added rigidity
• Threaded core and galley plugs (straight-thread port plugs with O-ring)
• NASCAR-inspired front oil feed on both lifter galleys
• Supports displacements up to 460 cubic inches
• 1-piece rear main seal

Compatibility Notes:

• Designed for use with M-6049-X306, X307, C3, D3, and Z304DA cylinder heads
• Not designed for production 302/351W or M-6049-Y302/Y303/X302/X303/X304/X305 cylinder heads
• Requires special length 1/2" head bolts M-6065-BOSS or head studs M-6014-BOSS
• Compatible with stock-style 302/351W timing cover (M-6059-D351 recommended)
• Fits factory Mustang oil pan with custom oil pick-up tube M-6622-BOSS302
• Compatible as a dimensional replacement for original 289–351 Windsor-style blocks

The Boss 351 Big Bore block is sold as a bare block and ships via LTL truck freight. Whether you're building a dedicated race engine or a street/strip powerhouse, the M-6010-BOSS351BB provides the strength, precision, and displacement potential to support your most demanding build.