ATK HP21M Ford 408 Stroker 430 HP Stage 2 Mid-Dress LB Long Block Crate Engine

Description

Eliminate small-block torque deficiencies with the ATK HP21M Ford Crate Engine 408 Stroker Mid-Dress package. Engineered for classic Mustangs, Broncos, and restomod trucks, this 6.7-liter Windsor stroker V8 produces 430 brake horsepower at 5,400 RPM. Outfitted with high-flow aluminum cylinder heads, dual-plane intake, distributor, water pump, balancer, and flexplate, this mid-dress long block accelerates vehicle project completion.

Machinists hand-select seasoned Ford 351W cast iron blocks, clearance-notching cylinder bottoms before align-honing main journals. A 4340 forged steel stroker crankshaft rotates with external 28-ounce imbalance weighting inside a one-piece rear main seal casing. Forged steel connecting rods attach to 4.030-inch forged aluminum pistons across a 4.000-inch stroke. A 10.0:1 compression ratio pairs with high-breathing aluminum cylinder heads. Oil capacity holds 5.0 quarts. Dry mid-dress weight totals 445 lbs.

Key Features of ATK HP21M

Restoration builders buy ATK HP21M crate engine mid-dress units to combine high-displacement stroker torque with their chosen induction system. The long block installs flush into vintage Ford engine bays using factory motor mount perches.

• 4.000-inch stroke crankshaft expands displacement to 408 cubic inches for massive torque gains.
• High-flow aluminum cylinder heads optimize high-RPM airflow while shedding front-end engine mass.
• Dual-plane aluminum intake manifold ensures balanced air-fuel distribution across all intake ports.
• Billet electronic distributor provides stable spark timing across the entire powerband.
• Performance hydraulic roller camshaft profiles produce aggressive valve lift without excessive valvetrain wear.
• Cast iron water pump circulates coolant through factory cooling systems without modification.
• External 28-ounce harmonic balancer counters crankshaft torsion during sudden acceleration pulls.
• Balanced ATK HP21M rotating parts isolate destructive vibration under sustained track loads.

Dynamic Mid Dress Dyno Output

Operating across an authoritative 2,200 to 5,600 RPM power band, this mid-dress 408 stroker produces 430 brake horsepower and 475 lb-ft torque on 91-octane pump gasoline. The performance hydraulic roller camshaft specifies 224 degrees intake duration at 0.050-inch lift with 0.540-inch valve lift. Manifold vacuum measures 15 in-Hg at an 800 RPM curb idle. Hot oil pressure runs between 45 to 65 PSI, keeping crank journals and overhead valvetrain hardware lubricated with pressurized oil during hard street acceleration.

Engine Bay Subframe Fitment Clearances

This Ford Windsor small block uses the classic Ford six-bolt bellhousing pattern, bolting straight to C6, AOD, and Tremec manual transmissions. The included 28-ounce balance flexplate accommodates automatic converters. Factory motor mount bosses align with stock frame brackets. The front-sump oil pan clears steering linkages and front crossmembers without chassis modifications.

Break-In Protocol Maintenance Duty Limits

Pre-lube engine oil passages with high-zinc 10W-30 mineral oil using a mechanical primer shaft before initial starter engagement. Fill and bleed coolant through the thermostat housing to eliminate trapped air pockets. This engine package is not engineered for supercharger boost exceeding 6 PSI, continuous RPM past 6,000, or raw marine sea water cooling.

• Drain break-in motor oil after the first 50 road miles.
• Renew synthetic or conventional motor oil every 3,000 miles.
• Inspect ignition timing, spark plugs, and distributor advance every 12 months.

Warranty Coverage Pallet Crate Manifest

A 12-Month limited warranty protects against material and manufacturing defects. The banded wooden pallet crate houses the mid-dress long block, aluminum cylinder heads, intake manifold, distributor, water pump, harmonic balancer, flexplate, oil pan, valve covers, dyno verification printout, and installation guide. Components ship sealed against oxidation.