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428 Block
Pontiac V8 428 Block
The Big-Journal Block — 428 Block for Pontiac V8s
The 428 is the big-journal factory Pontiac block: 3.25" mains and a larger standard bore than a 400, which is why it takes stroke so well. An assembled 428 short block arrives as a finished, internally balanced bottom end on a machined 428 block, waiting on your cam, heads and induction.
Butler builds it as a Custom Short Block with a long-rod H-beam rotating assembly in three strokes. All three run a cast or forged crank, Ross pistons in your choice of flat top, dish or dome, file-fit rings and a Viton rear main seal, assembled by a Butler engine specialist.
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More About 428 Block
1. Why Builders Start With a 428
The 428 is not just a 400 with more displacement. Its 3.25" main journals and larger factory bore change what the bottom end will tolerate, and they change what parts fit.
| Big mains | the 428 shares its 3.25" main size with the 421 and 455, so it takes the large-main cranks and the large-main rear main seal, not the 3.00" main parts that fit a 350, 389 or 400. |
| Bore room | Butler works the 428 around a 4.211" bore, which is more cylinder than a 400 gives you at the same stroke. |
| It is a core, not a catalog item | the 428 was built for a handful of years and good ones are finite. That is the argument for having it machined and assembled correctly the first time. |
2. The Three Strokes
Each stroke is a different crank in the same prepped block, and the displacement Butler lists comes with it.
| 4.210" stroke, 455-462 cu. in. | the mild stroker. A strong, streetable combination that does not need exotic clearance work. |
| 4.250" stroke, 455-462 cu. in. | the long-rod favorite, and the stroke most of Butler's 6.800" rod parts are built around. |
| 4.500" stroke, 487-495 cu. in. | the deep stroker. Butler recommends 4-bolt billet main caps at this stroke, because that much crank swing loads the main webbing hard. |
3. What Comes Assembled, and What You Still Owe
The short block covers the bottom end only. It is an SBK by Butler's definition: block plus rotating assembly, no cam and no heads.
| In the assembly | cast or forged crank, H-beam rods, Ross flat top, dish or dome pistons, file-fit rings, performance rod and main bearings, internally balanced, Viton rear main seal. |
| In the block | cleaned, magnafluxed, sonic tested, deburred, bored and honed with a torque plate, line honed with ARP main studs, deck squared, cam bearings and brass freeze plugs installed. |
| Still to buy | camshaft and lifters, timing set, cylinder heads, valvetrain, intake, oil pan and pump, and a neutral-balance flexplate or flywheel to suit an internally balanced assembly. |
Send Butler your head casting number or chamber cc with the order. Compression gets confirmed off your actual heads before the pistons are ordered, and on a 428 with a long stroke that is not a detail you want left open.
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.