495ci Pontiac Stroker V8 and TH400 Automatic Transmission

The 495ci Pontiac Stroker paired with a TH400 (Turbo-Hydramatic 400) is the ultimate “torque monster” combination for Pontiac purists. While Chevy fans usually go for a Big Block (454/502) to get this kind of displacement, the Pontiac 495 is a “Large Small-Block” design that fits in the same physical space as a 350 or 400, but delivers massive power.

In 2026, this combination is the gold standard for high-end GTO, Firebird, and Trans Am builds.

1. The Engine: 495ci Pontiac Stroker

A 495 is typically built using a 400ci block (4.12″ bore) with a 4.50″ stroke crankshaft. Unlike Chevy, all Pontiac V8 blocks (326–455) share the same external dimensions.

2026 Engine Valuation:

• Full Crate Build (e.g., Butler Performance): $16,000 – $22,000

• DIY Build (Parts & Machining): $9,000 – $13,000

2. The Transmission: TH400 Automatic

The TH400 is the only factory-style automatic that can reliably handle the 600+ lb-ft of torque generated by a 495 stroker without constant failure.

• Modifications for 2026: For a 495ci build, a standard TH400 isn’t enough. You need a “Stage 2” or “Stage 3” build featuring:

  • Forward Pattern Valve Body (or Manual Valve Body for street/strip).

  • Anti-Ballooning Torque Converter (2,800–3,200 stall speed recommended).

  • Hardened Input Shaft.

• Estimated Price (2026): $2,500 – $4,500 (depending on torque capacity).

3. Critical “2026 Health Check” & Build Tips

• The “Thin Wall” Problem: Pontiac blocks (especially the later mid-70s 400s) have thinner cylinder walls than older units. Before building a 495, sonic check the block to ensure it can handle the side-loading of a 4.50″ stroke.

• Oil System: Pontiacs have a unique oiling system. For a 495, a high-volume oil pump and a baffled 7-quart oil pan are mandatory. At 6,000 RPM, a 495 can suck a stock oil pan dry in seconds.

• Cooling: A 495ci engine generates immense heat. In 2026, you must use a high-performance 4-core aluminum radiator and dual electric fans (minimum 3,500 CFM) to keep it street-driveable.

• TH400 Fitment: If you are swapping this into a car that originally had a TH350 or Powerglide, you will need to shorten the driveshaft and move the transmission crossmember back.