ATK HP107M GM 383 Stroker 525 HP Stage 2 Mid-Dress LB Long Block Crate Engine

Description

Dominate local bracket drag races using the ATK HP107M GM Crate Engine 383 Stroker Mid-Dress package. Engineered for classic Chevrolet muscle cars, hot rods, and street-strip machines, this 6.3-liter small block produces 525 brake horsepower at 5,800 RPM. Complete with aluminum cylinder heads, intake manifold, distributor, water pump, harmonic balancer, and flexplate, this mid-dress long block accelerates project completion.

Engine builders select seasoned GM cast iron four-bolt main blocks, precision align-honing main journals and squaring block decks. A 4340 forged steel stroker crankshaft rotates inside a one-piece rear main seal with internal-external balance weighting. Forged 4340 H-beam connecting rods attach to 4.030-inch forged aluminum pistons across a 3.750-inch stroke. A 10.2:1 compression ratio pairs with high-breathing aluminum cylinder heads. Oil capacity holds 5.0 quarts. Dry long block weight totals 435 lbs.

Key Features of ATK HP107M

Street machine builders buy ATK HP107M crate engine mid-dress units to match 525 stroker horsepower with their own carburetor or EFI selection. The long block drops flush into classic GM engine bays using factory motor mount perches.

• 3.750-inch forged stroker crankshaft expands displacement to 383 cubic inches for massive acceleration.
• High-velocity aluminum cylinder heads optimize high-RPM airflow while reducing vehicle nose weight.
• Dual-plane aluminum intake manifold distributes balanced air-fuel charge to all cylinder runners.
• Billet electronic distributor provides stable spark timing across the entire 6,200 RPM range.
• Aggressive hydraulic roller camshaft profile produces broad power without excessive valvetrain wear.
• Cast iron water pump circulates coolant through factory cooling systems without modification.
• External-internal balanced harmonic balancer counters crankshaft torsion during hard acceleration pulls.
• Balanced ATK HP107M rotating components protect bottom-end bearings from destructive vibration.

Dynamic Mid Dress Dyno Output

Operating across an explosive 2,800 to 6,200 RPM power band, this mid-dress 383 stroker generates 525 brake horsepower and 490 lb-ft torque on 93-octane premium pump gasoline. The performance hydraulic roller camshaft specifies 236 degrees intake duration at 0.050-inch lift with 0.550-inch valve lift. Manifold vacuum measures 13 in-Hg at an 850 RPM curb idle. Hot oil pressure holds between 45 to 65 PSI, keeping rod journals and high-rate valvetrain hardware lubricated with pressurized oil under hard acceleration.

Engine Bay Subframe Fitment Clearances

This small-block Chevrolet engine utilizes standard GM 90-degree V8 transmission bellhousing patterns, bolting straight to TH400, 700R4, and manual transmissions. The included flexplate matches performance torque converters. Motor mount pads align with factory GM chassis crossmembers. The rear-sump passenger-car oil pan clears front suspension steering linkages and crossmembers without modification.

Break-In Protocol Maintenance Duty Limits

Pre-lube engine oil passages with high-zinc 10W-30 mineral oil using a mechanical primer before initial starter cranking. 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 6,500, 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.