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Crankshafts
Pontiac V8 Crankshafts
Cubic Inches Start Here — Crankshafts for Pontiac V8s
The crankshaft decides the displacement and sets the limit on how hard the engine can be run. On a Pontiac V8 the first question is never brand — it is main journal size, because the 326 through 400 use a 3.00" main and the 421, 428 and 455 use a 3.25" main, and nothing crosses over.
Butler splits this section by main size and then by material: cast, forged 4340, and billet, with cranks from Eagle, Scat, Molnar, Ohio and Bryant, plus factory Pontiac cranks turned and blueprinted by Lunati.
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More About Crankshafts
1. Which main journal does your block have
Get this wrong and nothing else on the page applies to you. It is the top-level split in this whole category.
| 3.00" main | 326, 350, 389 and 400 blocks, and the aftermarket blocks machined to match. Butler stocks cast and forged cranks in this size. |
| 3.25" main | 421, 428 and 455 blocks. Same idea, separate pages, separate parts. |
| Billet | A separate page, because a billet crank is specified rather than selected. |
2. Factory, cast, forged or billet
Butler's own crankshaft copy is direct about where each one belongs.
| Turned factory cranks | Butler starts with stock Pontiac cores that have had no spun bearings or other damage and sends them to Lunati to be cleaned, shot peened, crack checked, turned and blueprinted — turned no more than .020/.020, with the undersize confirmed once the order is placed so the right bearings go with it. |
| Cast | New cast pieces made with modern material and casting processes, recommended for street engines without power adders. Butler's reasoning for buying new: many factory cranks they check have stress cracks. |
| Forged 4340 | Described by Butler as a tremendous advantage in strength over cast, and as inexpensive insurance that leaves room to add power later. |
| Billet | Milled from 4340 chromoly or EN30B bar stock and CNC machined to your specification. |
3. Stroke changes more than displacement
Adding stroke reaches into the rest of the rotating assembly.
| Rod journal | Factory cranks use a 2.250" Pontiac rod journal. Most aftermarket stroker cranks are cut with a 2.200" big-block journal instead, which changes the rod and the rod bearing. |
| Rod length | Longer strokes pair with 6.700", 6.800" and 7.100" rods against 6.625" on stock-length combinations. |
| Balancing | Every rotating assembly Butler sells is balanced in its own shop and ships with a balance card. A neutral balanced crank must use a neutrally balanced flexplate, flywheel and balancer. |
Tell us the block, the displacement you are after and whether a power adder is in the plan. Those three answers narrow this section to one page.
3" Main- Cast Crankshafts for 326/350/389/400/Aftermarket Blocks 3" Main- Forged Crankshafts for 326/350/389/400/Aftermarket Blocks 3.25" Main- Forged Crankshafts for 421/428/455 Blocks Billet Crankshafts
Not sure what your Pontiac needs?
Email our tech team at tech@butlerperformance.com. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.