455 Swap
Short answer: A 455 swap is simple — all Pontiac V8s since 1967 share the same external dimensions (except the 301). Move your timing cover, water pump, pulleys, accessory brackets, and exhaust manifolds onto the 455 and it bolts right in. (Car Craft, Feb. 2001, covers a 326→455 swap with good photos.)
Watch these:
- Flywheel/flexplate: Pontiac used several crank-flange diameters — measure and confirm your flywheel/flexplate bolts on, or use the 455’s.
- Intake sealing: intake ports changed around 1972, so a later engine needs correct gaskets; block the heat crossover (thin metal) to prevent leaks if using a 1972-or-earlier intake.
- Weight: a 455 is heavier than a 326 — you may need new front springs if the suspension bottoms.
- Front dress: 1967–68 used an 8-bolt timing cover/pump; 1969 went to an 11-bolt with two pump heights (different pulleys/brackets). Source the cover, pump, pulleys, and brackets all from one engine to avoid pulley misalignment and thrown belts.
- Mount bosses: 1969-and-earlier blocks have two mount bosses; 1970+ blocks were cast with five (to fit early or late chassis) but may not be drilled/tapped — drill/tap as needed using a correct bracket as a guide, or use engine-change brackets (Year One, Performance Years, AMES).
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Content last modified: June 13, 2026 at 10:06 am
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