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389 Engine Rebuilder Assemblies- Stock Stroke
Pontiac V8 389 Engine Rebuilder Assemblies- Stock Stroke
Put It Back Together Right — 389 Engine Rebuilder Assemblies- Stock Stroke for Pontiac V8s
389 Engine Rebuilder Assemblies are the stock-stroke path: the 389 goes back together as a 389, with new parts chosen to work with each other instead of whatever the last machine shop had on the shelf. This is the shelf for a numbers-matching GTO, a Bonneville that still has to drive like a Pontiac, or any 389 that simply wore out.
Butler covers it three ways — a re-ring kit, a complete rebuild kit with cast or forged pistons, and a Butler/Ross custom balanced rotating assembly on the stock 3.750" stroke — all with Federal Mogul bearings and Butler-selected parts.
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1. Re-ring, rebuild, or full rotating assembly
How far down the engine came apart decides which of the three you need.
| 389 Re-Ring Kit | Rings in .030 over, Federal Mogul main and rod bearings in standard, .010" or .020" over, and a complete gasket kit with rear main seal and oil pan gasket options. For a 389 whose pistons and bores are still good and only needs to be freshened. |
| 389 Rebuild Kit | Pistons, pins, rings, rod and main bearings and the complete gasket kit, offered with cast hypereutectic or forged pistons in .030, .040 or .060 over. There is also the option to add a new cast or forged crank. |
| Butler/Ross balanced rotating assembly, 3.750" stroke | A cast or forged 3.750" crank, Ross forged flat top, dish or dome pistons, I-beam 6.625" rods, 980 wrist pins, Total Seal Classic Race rings, Federal Mogul or Clevite Performance bearings, internally balanced by Butler. |
2. Piston choice sets your compression — and your fuel
The rebuild kits publish their estimated compression by chamber size, which is the number that decides what you can pour in the tank.
| Cast flat top (-3.5cc) | Estimated 11.1-11.3:1 with a 68cc chamber and 10.7-10.9:1 with a 72cc chamber. Those figures require high-octane fuel — do not plan a pump-gas driver around them without talking it through. |
| Cast dish top (-17cc) | Offered in .058" over only, estimated 9.7-9.9:1 with 68cc chambers and 9.3-9.5:1 with 72cc. This is the pump-gas answer in the cast kit. |
| Forged flat top (-2cc) | Estimated 10.73:1 at 72cc, 10.07:1 at 78cc and 9.41:1 at 85cc. |
| Forged dish (-14cc) | Estimated 9.50:1 at 72cc, 8.99:1 at 78cc and 8.47:1 at 85cc. |
3. Things that catch rebuilders out
| Know your chamber cc before you order pistons | The same piston lands two full points apart between a small-chamber and a large-chamber head. Measure or identify the heads first. |
| Bearing sizes | Main and rod bearings come standard, .010" and .020" over, so the crank can be turned before the parts are ordered. Have the crank checked first. |
| Balancing | The Butler/Ross assembly is internally balanced in our shop and needs a neutral-balanced flywheel or flexplate and balancer to match. |
If the block is going out for boring anyway, the rotating assembly is usually the better buy, because the stroke, piston and balance work all get settled at once. If it is a hone-and-ring job, the re-ring kit does exactly what it says.
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.