Ford Performance Engineers have designed the replacement for the legendary BOSS 302 and 351 blocks using the latest technology and manufacturing techniques from both the production and racing worlds.  The BOSS block capability has been proven abound the world – both on the track and on the street.  By preserving many of the dimensions and features from the original 289-351 blocks, the BOSS blocks are compatible as replacements for use in just about any vehicle that used a Windsor style engine.  Cast from diesel grade iron and designed with added material in key areas, BOSS block strength is far superior to any Ford OE block ever produced. 


• 4.125" bore capacity, finished at 3.990" to 3.995" rough bore. Also available in big bore version, part number: M-6010-B302BB
• 8.2" deck height, finished at 8.200" plus .010" to .015"
• Designed with optimized cylinder wall length for stroker applications up to 3.5" with no grinding or clearancing.  (Depends on crank/rod manufacturer)
• Splayed 4-bolt main on 2, 3, 4, main caps
• 2-bolt main on first and fifth main caps
• Main bearing bores finished to low limit
• Finished lifter bores
• Machined to accept factory roller lifter guides and lifter guide retainer
• Fits factory 1979 - 1995 Mustang oil pan with custom oil pickup tube, part number: M-6622-BOSS302
• NASCAR inspired front oil feed on both lifter galleys.
• Revised cooling system passageways
• Siamese bore with drilled coolant crossover holes (Except on M-6010-B302BB)
• Increased bulkhead material
• Threaded core and galley plugs (straight thread port plugs with O-ring)
• Requires special length 1/2" head bolts M-6065-BOSS or head studs M-6014-BOSS recommended with M-6049-X306/X307/X2/Z304DA/Z2 heads
• Designed for use with the following heads-
• X306
• X307
• X2
• C3
• D3
• Z304DA 
• Z2
• GT40P
• Not designed for the following heads 
• Production 302/351W [GT40P is compatible]
• M-6049-Y302
• Y303
• X302
• X303
• X304
• X305
• Uses common OD cam bearings M-6261-J351/R351
• Unique cam plug M-6026-S351 included
• M-6051-S331 or M-6051-CP331 head gasket recommended
• Designed to be compatible with vehicles equipped with the original 302 and 351W block
• Designed to use stock type timing cover, M-6059-D351 recommended (includes fuel pump provision)
• Fits factory Mustang oil pan with custom oil pick-up tube M-6622-BOSS302
• M-6026-A Service Replacement Plug and Dowel Kit available separately: 
• Includes O-ring threaded plugs, black anodized aluminum plugs with Buna "O" rings for the oil galleys, water drains and core holes, and dowels for front cover, clutch housing and cylinder heads
• Retains clutch cross shaft pivot hole
• Original Style oil filter location
• Original motor mount boss locations
• Original bell housing pattern

• Weighs approximately 175 lbs.
• Great price and value
• The foundation for 8.2" deck projects

Proven performance - used in Ford Performance sealed 347cid race engines and Ford Performance high performance crate engines, a proven winner out of the crate with thousands of laps to demonstrate durability. 

Ford Performance BOSS Blocks 

For cylinder head compatibility questions, please contact the Ford Performance Techline.