In the world of racing and performance, BIGGER is always better.  Ford Racing gets it -  and that's why it offers BOSS small blocks in Big Bore versions.  The Ford Racing BOSS blocks are designed to be a replacement for the legendary BOSS 302 and BOSS 351 blocks using the latest technology and manufacturing techniques available.  Cast from diesel grade iron with siamese bores, thick cylinder walls and decks, BOSS block strength is far superior to any Ford production block ever offered. 


Ford Racing Big Bore 351 blocks make it simpler and more economical to build really BIG small blocks.  To insure the most precise bore location, concentricity and integrity, the BOSS Big Bore blocks are machined an additional .125" during the initial block fixturing and boring stage.  With an unfinished bore size of 4.120", Ford Racing BOSS 351 Big Bore blocks make really BIG small blocks - as big as 460 cubic inches!


The Ford Racing BOSS block capability has been proven around the world, both on the track and on the street.  And, all Ford Racing BOSS blocks are cast and machined to the highest industry standards in the USA. 

  • Same as M-6010-BOSS35195 except allows for bigger bore by deleting coolant crossover holes between cylinders
  • Finished at 4.120" rough bore. Designed for minimum bore wall thickness .180" @ 4.125" (Sonic check recommended for bores greater than 4.125")
  • 9.5" deck height, finished at 9.500" plus .010" to .015"
  • Maximum recommended stroke 4.250", clearance dependent on crankshaft/connecting rod manufacturer
  • Splayed 4-bolt main on 2, 3, 4, main caps
  • 2-bolt main on 1 and 5 main caps
  • Main bearing bores finished to low limit
  • 2.749" main journal diameter (stock 351C size)
  • Finished lifter bores
  • Machined to accept factory roller lifter guides and lifter guide retainer
  • NASCAR inspired front oil feed on both lifter galleys
  • Revised cooling system passageways
  • 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 M-6049-X306/X307/X2/C3/D3/Z304DA/Z2 cylinder heads. Not designed for production 302/351W or M-6049-Y302/Y303/X302/X303/X304/X305 cylinder heads
  • Uses common OD cam bearings M-6261-J351/R351
  • Unique cam plug M-6026-S351 included
  • Designed to be compatible with the original 302 and 351W blocks and includes the following features:
  • Designed to use stock type timing cover, 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 197 lbs.
  • Great price and value
  • The foundation for big bore 9.5" deck projects

 Ford Racing BOSS Blocks 

Part Type
Engine: Engine Blocks
Instruction Sheet
Warranty Availability
Not Available
Package Dimensions
25" x 24" x 31"
Package Weight
221 lb(s)
UPC Code
Country of Origin
United States