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400 Blocks (406-495 cu. In.)
Pontiac V8 400 Blocks (406-495 cu. In.)
One Block, Three Directions — 400 Blocks (406-495 cu. In.) for Pontiac V8s
The 400 is the most common Pontiac V8 block on the bench, and it is the one with the widest range of outcomes. The same casting can go back together as a stock-stroke 400 or come out as a 495 ci super stroker, and the rotating assembly is the part that decides which.
Butler splits 400 block work into three shelves — stock-stroke rebuilder assemblies and kits, stroker assemblies up to 4.250", and super stroker assemblies up to 4.500" — with both Butler/Ross custom packages and Eagle Competition and Street/Strip kits, all balanced through the Butler Process.
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More About 400 Blocks (406-495 cu. In.)
1. Pick the shelf that matches your build
Everything under the 400 block is organised by stroke, because stroke is what separates these three groups.
| 400 Engine Rebuilder Assemblies — stock stroke | Re-ring kits, complete rebuild kits with cast hypereutectic or forged pistons, and balanced 406-413 ci assemblies on the stock 3.750" stroke, including a build-your-own version for shops that do their own assembly. |
| 400 Stroker Rotating Assemblies — up to 4.250" stroke | The deepest shelf in the tree. Butler assemblies at 4.000", 4.210" and 4.250" stroke, plus Eagle Competition and Street/Strip kits at 461 and 468 ci. |
| 400 Super Stroker Rotating Assemblies — up to 4.500" stroke | 4.375" and 4.500" stroke packages taking the 400 block to 471-480 ci and 487-495 ci. |
2. Butler assemblies and Eagle kits are not the same product
| Butler/Ross assemblies | Built around genuine Ross forged pistons on Butler's exclusive true-Pontiac strut-style forging, with long rods sized to the stroke, Total Seal rings, bearings selected for clearance and internal balancing done here. Compression is specified to your heads. |
| Eagle kits | Fixed combinations at defined bores and displacements, with forged 4340 rods, ARP 8740 capscrew rod bolts, forged Mahle pistons and file-fit plasma-moly rings. Competition kits use H-beam rods and a forged crank; Street/Strip kits use a cast crank and Butler's exclusive FSI I-beam rods. |
3. Three block facts worth checking first
| 557 castings | Butler does not recommend long-stroke combinations in blocks whose casting numbers end in 557 — thinner main webbing. We suggest limiting those to 4.000" stroke and under 500 hp. |
| Bore starts at .030" over | That is deliberate, so the block cleans up and the rings seat within spec. Larger bores are available, and displacement is quoted as a range because it moves with the bore. |
| Everything must be balanced | Every rotating assembly Butler sells, regardless of brand, has to be balanced before it goes in an engine. Eagle kits ship unbalanced by design; our shop balancing is available on any of them. |
Most 400 owners end up choosing between a fresh stock-stroke rebuild and a 4.250" stroker, and the deciding factors are usually the heads you already have and the fuel you plan to run. Tell us both and the shelf picks itself.
400 Stroker Rotating Assemblies- up to 4.250 Stroke
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.