Listing Title:1965 Chevy L78 Block Bored to 427 (+.030) 431ci Short Block - Cast 3855962 Stamp T0717IEItem Description : Up for sale is a legendary piece of Chevrolet muscle history: a freshly machined 1965 Mark IV L78 Big Block Short Block package. This is the highly coveted, heavy-wall 3855962 casting block. It has been sonic-checked and safely punched out from its original 396 configuration to a 427 bore size, finalized at .030 overbore (4.280" cylinder bore). Combined with the factory 3.76" stroke, it displaces 431 cubic inches of pure period-correct power. Machine Status & Clearance Specifications: Block Work: Professionally bored and honed by an automotive machine shop. Crankshaft: Factory GM 6223 Forged Steel Crank turned .010/.010 and freshly polished. Assembly Status: Block features brand new cam bearings, new main bearings, and a new rear main seal. The crank has been personally installed to precise tolerances. Specs Available: All exact micrometer clearance measurements were carefully recorded during assembly and are written down for the buyer's review. Connecting Rods: Professionally checked, sized, and ready for final assembly. Block Casting & Identity Specs: Block Casting Number: 3855962 (Famous early thick-wall block capable of 427 overbore)Casting Date Code: E 19 5 (Cast on May 19, 1965)Front Pad Stamp: T0717IET: Assembled at the Tonawanda, NY engine plant0717: Assembled on July 17, 1965IE: Original factory code designating the highest-tier Special High Performance 425 Horsepower L78 configuration (solid lifter, rectangular-port setup paired with a manual transmission)Pad Condition: The front pad stamp features the factory-correct surface appearance; no deck altering was performed during machine work to strictly preserve the authenticity of the numbers.Included High-Performance Components (Not Yet Installed):Cylinder Heads: Pair of original, ultra-rare 1965 Casting #3856208 "Porcupine" Rectangular Port, closed-chamber iron heads. Both are factory date-coded F165 (June 16, 1965), matching the block's timeline perfectly.Pistons: Vintage TRW L2236 forged aluminum dome pistons, yielding a period-correct, high-performance 11.0:1 compression ratio build.Logistics & Shipping:Terms: Local pickup preferred.Freight: Willing to secure safely to a heavy-duty wooden pallet and ship via freight carrier at the buyer's expense.Serious collectors and vintage hot rod builders only. Please message me with any questions or if you want to see the physical components and spec sheet.
