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3.25" Main- Cast Crankshafts for 421/428/455 Blocks
Pontiac V8 3.25" Main- Cast Crankshafts for 421/428/455 Blocks
Big Journal, Fresh Casting — 3.25" Main- Cast Crankshafts for 421/428/455 Blocks for Pontiac V8s
The 421, 428 and 455 all ride on a 3.25" main journal, and a cast crank for those blocks is a different casting from anything that fits a 400. This page is where a big-journal Pontiac gets a fresh crank without stepping up to forged.
Butler stocks Eagle cast cranks here in the 4.210" stroke on a 2.250" Pontiac rod journal — the factory 455 stroke, on stock-length rods — and a 4.250" version on the 2.200" big-block journal, plus the standard Pontiac crank key.
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More About 3.25" Main- Cast Crankshafts for 421/428/455 Blocks
1. Two strokes, two very different builds
The stroke numbers on this page are close together. What they ask of the rest of the engine is not.
| 4.210" on the 2.250" Pontiac journal | The factory 455 stroke with the factory rod journal, listed by Eagle against a 6.625" rod length. This is the replacement crank for a 455 going back together on stock-length rods, and it is the one a 421 or 428 owner uses to pick up the full 455 stroke. |
| 4.250" on the 2.200" big-block journal | Forty thousandths more stroke, but a different rod journal entirely, which means big-block-journal rods and a different rod bearing. Treat it as a stroker build, not a swap. |
| Hub register | 2.75", same as the rest of the Pontiac crank range. |
2. Cast on a 455 — where the line is
The 455 makes torque without trying, which is exactly why the crank choice matters.
| Street, naturally aspirated | Butler recommends cast cranks for street engines without power adders. A 455 built for torque and driven on the street sits comfortably inside that. |
| Why new instead of the original | Butler's crankshaft copy notes that many factory cranks they inspect carry stress cracks. A big-journal core that has been in service since the early seventies is worth replacing rather than gambling on. |
| Where it stops | Add boost, nitrous or sustained high rpm and the forged 3.25" main page is the answer. Butler frames forged as inexpensive insurance that leaves room to add power later. |
3. Ordering around the crank
Three things to settle at the same time as the crank itself.
| Main bearings | A new cast crank takes standard mains from the 421-428-455 group. A turned crank takes the matching undersize — order to the measured journal, not the engine. |
| Rods | The 2.250" Pontiac journal keeps the stock 6.625" rod length available. The 2.200" big-block journal moves you into the stroker rod groups. |
| Balancing | Every rotating assembly Butler sells is computer balanced in house to the rest of the assembly, and ships with a balance card documenting the weights. Butler will also balance a crank to a bob weight you supply. |
If you already have the block and the heads, the stroke question comes down to which rods you want to run. Call with the rod length and it takes one minute.
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.