Pontiac 455 V8 Engine for Sale | OEM 7.5L 455ci Big-Inch Motor

Description

Engine Background

Pontiac’s 455 is the biggest production V8 the division ever released. It debuted for the 1970 model year when engineers opened the bore on the existing 428 to 4.155 inches and lengthened the stroke to 4.21 inches, yielding 457.6 actual cubic inches and producing one of the strongest torque curves of the muscle era. The 455 HO at its high point delivered 370 hp and 500 lb-ft of torque, placing it among the most muscular street engines on sale anywhere during that period.

A distinguishing characteristic worth noting: every Pontiac V8 from the 326 through the 455 uses identical external block dimensions and matching motor mount locations. That detail means a 455 will drop into any chassis that originally carried a Pontiac V8, provided the supporting components are correct, which keeps swap projects manageable.

From its launch through 1976, the 455 motivated the GTO, Firebird, Trans Am, Grand Prix, LeMans, Catalina, Bonneville, and Grand Ville. For any serious Pontiac restoration today, a documented used OEM unit with verified casting numbers and a known variant is the right starting point.

When Replacement Becomes Necessary

• Audible knock or rattle under load, typically pointing to rod or main bearing wear on high-mileage cores
• Blue exhaust smoke at startup or under throttle, usually traced to valve stem seals or worn rings
• Lost compression in one or more cylinders, often from scored bores, broken rings, or a failing head gasket
• Oil pressure dropping at warm idle, indicating main bearing clearance has opened past spec
• Coolant mixed with oil or white exhaust vapor, frequently the result of head gasket failure on late-emissions blocks that have been run hot
• Rough idle that worsens as temperature climbs, a recognized symptom of cam lobe wear on aging Pontiac V8s
• Heavy oil usage past one quart per 1,500 miles, pointing to ring or valve seal failure

Known Weak Points

• Reduced output on late-emissions blocks: 1975 and 1976 455s could be as low as 200 hp with 7.6:1 compression. Acceptable as a stock-for-stock swap but not the right core for a performance program. We confirm the year and trim before anything ships.
• 2-bolt mains on 1973-onward base blocks: Beginning in 1973, standard 455 blocks moved from 4-bolt to 2-bolt main caps. Super Duty units kept the 4-bolt setup. If your build calls for 4-bolt mains, flag it during the quote.
• Round-port versus D-port head conflict: The 1970 base 455 ran D-port heads. From 1971, HO engines used round-port heads requiring an entirely different intake. Head castings are documented on every shipped unit.
• Oil pump driveshaft wear: High-mileage Pontiac V8s commonly develop wear in the oil pump drive area. Each unit is inspected and oil pressure noted.
• Two-piece rear main seal seepage: Older units with two-piece rear mains will seep. Gasket surfaces are checked and any seepage is disclosed prior to shipment.

Known Variants by Year and Output

Common Casting Numbers

What Ships and What Does Not

INCLUDED (Long Block): Block, crankshaft, pistons, connecting rods, camshaft, cylinder heads, valve train, oil pan, timing cover, and water pump where present.

NOT INCLUDED: Intake manifold, carburetor, exhaust manifolds, distributor, ignition system, alternator, power steering pump, A/C compressor, starter, flexplate or flywheel, accessory brackets.

Core policy: No core return required. Your existing engine stays with you.

Direct-Fit Vehicle Applications

Swap compatibility: The 455 bolts into any 1967-and-newer Pontiac originally equipped with any Pontiac V8. Transmission pairings: TH400 (strongest), TH350, and Muncie 4-speed M20/M21/M22.

Search Terms Buyers Use

Pontiac 455 | 455 Pontiac engine | Pontiac 455 motor | 455 HO engine for sale | 455 Super Duty for sale | Pontiac GTO engine for sale | Pontiac Trans Am 455 engine | Pontiac Firebird 455 | 455 Pontiac big block | Pontiac 7.5L engine

Used OEM Versus Professional Rebuild

Used OEM is generally the better path for a GTO, Trans Am, or Firebird restoration where period-correct hardware matters. Our 455 units are compression tested and ship with casting numbers and variant identification documented. A specialist rebuild makes more sense for a show car or a build with precise tolerance requirements. Expect rebuilt HO and SD units in the $5,000 to $9,000-plus range from established Pontiac shops. Contact us if you want to discuss sourcing strategy.

Inspection Workflow

• Compression measurement on all 8 cylinders with per-cylinder pressure logged
• Block walk-through covering cracks, deck condition, journal scoring, and thread integrity
• Leak-down check on every gasket surface for active oil or coolant seepage
• Valve cover removal to assess sludge accumulation and any cam wear indicators
• Casting number, date code, and variant verified with D-port or round-port head identified
• Main cap configuration confirmed (2-bolt versus 4-bolt) before shipping

Pre-Purchase Buyer Notes

• Identify your variant: HO units (round-port heads, 1971-1973), Super Duty (1973-1974, rarest), and base 455s each behave differently. Tell us what you need on the call.
• D-port versus round-port intake: An HO engine requires a round-port-specific intake manifold. A D-port intake cannot mount on an HO block without swapping heads.
• 4-bolt versus 2-bolt mains: All pre-1973 standard 455s and all Super Duty blocks use 4-bolt mains. Post-1972 base engines moved to 2-bolt. Specify if 4-bolt is mandatory.
• Crankshaft cross-compatibility: The 455 crankshaft interchanges with the 400, opening up stroker build possibilities.

Why Part Nests

• Variant identification before payment, with HO, SD, or base confirmed alongside head type and main cap configuration
• Casting numbers and date codes recorded for every unit in inventory
• Compression results logged across all 8 cylinders and shared before order confirmation
• Fitment verified against your specific Pontiac chassis before shipment
• No core return required, keep your existing engine
• Free freight pallet delivery to every state with no hidden surcharges
• 15 day replacement warranty covering internal engine defects
• Call (240) 306-7051 to speak with someone fluent in 455 variant differences, casting identification, and Pontiac restoration practice