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Aftermarket Block
Pontiac V8 Aftermarket Block
Past The Factory Range — Aftermarket Block for Pontiac V8s
Aftermarket Block rings start where the factory Pontiac bore range ends. An IA II block gets bored to what the build calls for, typically in the 4.310" to 4.375" range, and no production Pontiac ring set reaches that far. Every set on this page is file fit, because at these sizes the end gap is always set on the bench.
Butler stocks Total Seal file fit sets in Classic Race, gapless top with a Napier style second, and AP stainless top, alongside the Butler IA II short block and builder kit packages those rings go into.
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1. The bore sizes an aftermarket block actually runs
These are not overbores of a production casting. They are the sizes an IA II block is built at from the start.
| 4.310" | Total Seal Classic Race file fit, supplied as a 4.315" ring, 1/16, 1/16, 3/16. |
| 4.350" | Classic Race file fit as a 4.355" ring. This is the bore Butler's own IA II builder kits are specified around with Ross pistons built for Butler. |
| 4.375" | Classic Race file fit as a 4.380" ring, the largest set on this page. |
| Why no drop in sets | At these bores the engines are making serious cylinder pressure. The end gap has to be chosen for the application, so the rings arrive oversize and get filed. |
2. Ring face options at big bore
| Classic Race | The baseline file fit set, available at 4.310", 4.350" and 4.375". |
| Gapless top with Napier style second | Total Seal builds this at 4.350" and 4.375". The gapless top closes the path blow-by takes past the top ring, and the Napier second is shaped to scrape oil down the wall. |
| AP stainless top | A C-33 chrome nitride coated stainless top ring in file fit at 4.350", for a harder duty cycle. |
3. What the rest of the combination looks like
Butler's aftermarket block packages give you the context these rings live in.
| Displacement | Butler's IA II short block and builder kit packages run 505 to 541 cubic inches. |
| Crank and rods | 4.250" to 4.500" stroke forged or billet cranks on 6.800" H-beam rods with ARP 2000 bolts. |
| Pistons | Ross pistons built for Butler at a 4.350" bore, with compression ratio specified to the heads. |
| Block prep | Sonic tested, completely deburred, bored and honed with a torque plate, line honed, deck squared, cam bearings installed. A torque plate hone is what makes a file fit ring gap mean anything. |
4. Ring thickness and what the piston dictates
| 1/16, 1/16, 3/16 | The pack every Total Seal set on this page is built in, and the groove a custom Ross piston for a big bore Pontiac is normally cut for. |
| Confirm against the piston | A custom piston can be ordered in a different groove thickness. The block does not decide the ring pack, the piston does, so have the piston part number in hand. |
| Buy them together | On an aftermarket block build the pistons are made to order anyway. Specifying the rings at the same time avoids a mismatch that only shows up at assembly. |
5. Fitting file fit rings
Square each ring in the cylinder it will live in, measure the gap with a feeler gauge, file it square, deburr it and keep it with that bore. The gap you choose should reflect what the engine will actually see, and on a 500-plus cubic inch Pontiac that usually means more gap rather than less. If the bore size or ring thickness you need is not shown, Butler will either have it in stock or can get 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.