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Aftermarket Block
Pontiac V8 Aftermarket Block
Built To The Block — Aftermarket Block for Pontiac V8s
Aftermarket Block pistons are a different conversation than a factory Pontiac rebuild. An IA II block does not share a production bore spacing chart, so there is no shelf part number. Every piston is specified to the finished bore, the stroke and the compression ratio the build is aiming for.
Butler covers this with fully custom Ross Racing Pistons in any bore and any stroke, flat, dish or dome, and DSS custom 2618 forged sets up to a 4.200" bore in any stroke. Both are specified by Butler's engine techs against the rest of the rotating assembly.
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1. Why there is no off-the-shelf part number
An aftermarket Pontiac block is bored to what the builder wants, not to a factory size. That makes the piston a made-to-order part every time.
| Ross custom | Any bore, any stroke, flat top, dish or dome, sold in sets of four or eight. Ross builds these on the Pontiac-specific forging developed for Butler, in 2618-T61 aluminum. |
| DSS custom | 2618-T6 forgings up to a 4.200" bore in any stroke, in flat top or dish, with your choice of rings and pins. |
| Specified, not guessed | Butler asks for the bore, the stroke, the rod length, the chamber volume and the compression ratio you want. The piston is then designed to land on it. |
2. Where the numbers usually land on an IA II build
Butler's own aftermarket block packages give you a sense of the territory, and they are the best reference point for what the rest of the assembly will look like.
| Bore | Butler's IA II builder kits are specified around a 4.350" bore with Ross pistons built for Butler, and the Total Seal ring sets stocked for aftermarket blocks run 4.310", 4.350" and 4.375". |
| Stroke | 4.250" to 4.500" on a forged or billet crank, which is what pushes those packages into the 505 to 541 cubic inch range. |
| Rods | 6.800" H-beam rods with ARP 2000 bolts on the Butler kits, which fixes the compression height the piston has to be cut to. |
| Pins | Butler's aftermarket block packages list a .990" pin, which is the size most large-bore custom pistons here are built around. |
3. Before you order
| Finish the block first | Bore and hone with a torque plate, then order pistons to the measured bore. Custom pistons are not returnable. |
| Rings are file fit | At these bore sizes the ring sets Butler stocks are file fit, so the ring gap is set to the application on the bench. |
| Lead time is real | A fully custom dish piston is a made-to-order part with a real production window. Build that into the schedule. |
Call Butler with the block, the crank and the heads you have committed to. The piston is the last part of the rotating assembly that should get locked in, because everything else defines it.
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.