086515 BMP LS Block Chevy LS 4.125 Bore

The ultimate in replacement for Chevrolet LS1, LS7 or C5R blocks, The BMP LS  block is cast from 357-T6 aluminum, the absolute strongest available, and has important improvements that even factory race blocks don’t have. This translates into engine builders being able to obtain more power and enjoy improved reliability with BMP LS based engines.

Let’s start at the bottom end. Main caps made of 1045 alloy steel billet are employed. This material is tougher than the 1020 steel used by others. The caps are located by ring dowels and secured with 200,000 psi tensile strength 7/16” ARP main studs and 8mm cross-bolts. It’s important to note that the BMP LS uses a priority main oiling system, which feeds the crankshaft first and the top-end last. Others feed the top-end first and can starve the main bearings. Water jackets are redesigned to provide more support around the cylinder – important for big boost applications. They also enhance cooling.

Bill Mitchell Products also recognized that in order for engine builders who employ power adders to maintain high combustion pressures with complete reliability it was essential to improve the sealing of the LS. With this in mind BMP’s engineering team added provisions for the optional use of two extra head studs per cylinder. They are designed to work in concert with the BMP LS 12° LS7 cylinder heads, which also have the extra bolt holes. Please note that the cast iron GM LSX block and the Bill Mitchel Products LS block do not have identical locations for the extra head bolts, however, standard 4-bolt GM LS heads will fit.

Another way that BMP has improved upon the quality of its LS block is through the machining process (which is to QS9000 standards). All BMP LS blocks are CNC machined in only two fixturing positions, which prevents the problems that can occur with production line blocks that are machined in multiple operations and the tolerances stack from one machine to the next. Bottom line, The BMP LS is the most advanced, precision made block on the market for LS applications!

TECHNICAL SPECS

MATERIAL: 357-T6 aircraft aluminum alloy 
DECK HEIGHTS: 9.240 or 9.800"(.600" minimum deck thickness)
MOTOR MOUNTS: LS1 and early small block Chevy
HEAD STUDS: Provisions to use 2 extra studs per cylinder (optional)
BORE SIZES: 4.000" and 4.125" (w/.100" dry sleeves & .300" support
CAM BORES: Can be machined up to 60mm
MAX BORE SIZE: 4.155
STUD HOLES: Counter bored to eliminate distortion
COMPONENTS: Accommodates all standard GM LS-series
OIL SYSTEMS: Can accommodate dry sump (scavenge p/u at rear)
CRANK CLEARANCE: 4.500" stroke
MAIN CAPS: Billet steel C5R-style with 200,000 psi ARP main studs
MAIN CAP DESIGN: All 5 Caps are 4 Bolt Design w/ all 5 caps side bolted as well.
MAIN CAP LOCATORS: Stock Register & Ring Dowels at the center studs
MAIN CAP HARDWARE: ARP ½” Stud Kit
REAR MAIN SEAL: One piece Chevy LS
LUBRICATION: Priority main (feeds crankshaft first and top-end last)
WEIGHT: Approximately 130 lbs. with sleeves