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3.25" Main- Forged Crankshafts for 421/428/455 Blocks
Pontiac V8 3.25" Main- Forged Crankshafts for 421/428/455 Blocks
Stroke on Top of Stroke — 3.25" Main- Forged Crankshafts for 421/428/455 Blocks for Pontiac V8s
A 421, 428 or 455 already has the big 3.25" main journal and a long factory stroke. A forged 4340 crank in that block is how you add cubic inches on top of cubic inches, or simply put a crank under a 455 that will survive rpm the factory piece never saw.
Butler stocks Eagle, Scat, Molnar and Ohio here from 4.000" through 4.500" of stroke, on both the factory 2.250" Pontiac rod journal and the 2.200" big-block journal, with Eagle's ESP Armor finish available on the 4340 line.
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1. What is on the shelf, and for which block
The big-journal forged range is tighter than the small-journal range, because the 455 starts with a long stroke already.
| 4.000", 2.250" Pontiac journal | Molnar's forged crank in this stroke is catalogued specifically for the 421-428 block. That is the forged replacement for a 421 or 428 keeping factory geometry and 6.625" rods. |
| 4.210", 2.250" Pontiac journal | Eagle's forged crank at the factory 455 stroke with the factory rod journal, listed against a 6.625" rod. A forged 455 crank that does not force a rod and piston change. |
| 4.250", 2.200" big-block journal | Eagle, Scat and Ohio all build this one. Eagle lists a 6.800" rod, Scat lists 6.700" or 6.800". |
| 4.500", 2.200" big-block journal | Eagle and Scat. This is the biggest stroke Butler catalogues on the 3.25" main and it puts real cubic inches under a 455 block. |
2. Keep the Pontiac journal or move to big-block
On the big-main blocks this decision has a specific consequence, because the factory 455 stroke is available both ways.
| Stay on 2.250" Pontiac | The 4.000" and 4.210" cranks here. You keep the 6.625" rod length and Pontiac-journal rod bearings, which makes this the least disruptive forged upgrade available for a 455. |
| Move to 2.200" big-block | Required for the 4.250" and 4.500" cranks. Lighter big end, far wider rod selection, and big-block rod bearings — but the rods and pistons change with it. |
| Hub register | 2.75" throughout, same as the rest of the Pontiac range. |
3. Why forged on a big-inch Pontiac
Butler's position on this is consistent and worth reading before you decide to save money on the crank.
| The case for it | Butler describes forged cranks as a tremendous advantage in strength and durability over cast, and as inexpensive insurance to protect the engine even if it is not strictly needed at your current power level. |
| Room to grow | A solid bottom end means you can raise the power later without worrying about a costly breakdown. On a 455 that already makes torque, that headroom matters. |
| Scat's spec | Premium non-twist 4340 forgings, precision ground and micro polished, heat treated and ion nitrided, with straight shot and chamfered oil holes and large radii on all journals. |
| Eagle ESP Armor | A surface finishing process unique to Eagle — not a coating, not a chemical etch. It reduces bearing friction, slows oil heating, reduces windage losses and improves corrosion resistance, and carries a one year limited warranty against breakage on 4340 cranks and H-beam rods. |
4. Ordering and balancing
The crank is one line on an order that really has four lines in it.
| Bearings | A new forged crank takes standard mains out of the 421-428-455 group, and rod bearings sized to whichever rod journal you chose. |
| Rods and pistons | Rod length and piston compression height fall out of the stroke. Order them together or expect to order twice. |
| The Butler Process | Every rotating assembly Butler sells is balanced in house. Rods and pistons are weighed and pin fitted, the crank is computer balanced to the rest of the assembly, and a balance card with the weights ships with it. Butler also balances cranks to a customer-supplied bob weight. |
If you are building a 455 for the street and want it to stay together at rpm, the 4.210" forged crank on the Pontiac journal is the low-drama answer. If you want the cubic inches, plan the rods and pistons at the same time.
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.