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tech notes

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.


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-BOSS35192 except allows for bigger bore by deleting coolant crossover holes between cylinders
  • 4.185" bore capacity (sonic check recommended), finished at 4.12" rough bore
  • 9.2" deck height, finished at 9.200" plus .010" to .015"
  • Maximum recommended stroke 4.00", 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
  • 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-X306/307/Z304DA heads
  • Designed for M-6049-X306//X307/C3/D3/Z304DA 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
  • Retains clutch cross shaft pivot hole
  • Original Style oil filter location
  • Original motor mount boss locations
  • Original bell housing pattern
  • Weighs approximately 195 lbs.
  • Great price and value
  • The foundation for big bore 9.2" deck engine projects

 Ford Racing BOSS Blocks 


Package Dimensions:
15 x 19.5 x 23
Package Weight:
214 lbs
Part Type:
Engine: Engine Blocks
Instruction Sheet:
Not Available
Warranty Availability:
Not Available
Country of Origin:
United States
UPC Code:
Catalog Page Number: