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350 Block
Pontiac V8 350 Block
Standard Through .060 Over — 350 Block for Pontiac V8s
350 Block rings run their own bore range, from a 3.875" standard bore out to 3.935" at .060" over. That is smaller than every other Pontiac V8 ring set Butler carries, so a 389 or 400 part number will not cross over no matter how close the numbers look.
Butler stocks Sealed Power moly-faced replacement sets in standard, .030", .040" and .060" over for a stock rebuild, and Total Seal Classic Race sets in both drop-in and file fit for performance builds.
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More About 350 Block
1. The four stock replacement sizes
The Sealed Power Speed-Pro sets cover a normal Pontiac 350 rebuild, each one cut to a specific finished bore.
| Standard bore, 3.875" | For a block that cleaned up without an overbore. |
| .030" over, 3.905" | The most common rebuild size on a 350. |
| .040" over, 3.915" | The next step when a cylinder needs more cleanup. |
| .060" over, 3.935" | The practical limit on most factory 350 castings. |
| Ring pack | All four use a 5/64" top, 5/64" second and 3/16" oil ring, with a moly-faced top ring, sold as a complete set for all eight cylinders. |
2. Total Seal Classic Race, drop in or file fit
| 3.905" drop in | A Classic Race set pre-gapped for a 3.905" bore in a 1/16, 1/16, 3/16 pack. Less work on the bench, no gap adjustment available. |
| 3.905" file fit | Supplied as a 3.910" ring so you can file the end gap to your combination. |
| 3.935" file fit | Supplied as a 3.940" ring for a .060" over 350. |
| Which to pick | A drop-in set is fine on a mild street rebuild. Go file fit if you are running a power adder, a lot of timing or a lot of rpm, because the gap needs to be set for the heat the engine will actually make. |
3. Matching the ring to the piston
| Groove thickness rules | The Sealed Power sets are 5/64, 5/64, 3/16, which suits a stock or replacement piston. Total Seal Classic Race sets here are 1/16, 1/16, 3/16, which suits a performance forged piston. They are not interchangeable. |
| Metric grooves | Some DSS forged 350 pistons use a 1.0-1.0-3.0mm or 1.2mm, 1.2mm, 3mm pack and include the rings. Do not buy a second set until you have read the piston listing. |
| Measure, then order | Butler's own advice on these sets is to match the ring set to the finished bore and to call if you are unsure what the block came out at. |
If you do not see your exact bore or ring thickness, Butler either stocks it or can get it. Give them the piston part number and the honed bore size and the ring set sorts itself out.
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.