The Pontiac 389 was a 389-cubic-inch V8 produced for the 1959 through 1966 model years. Its bore and stroke were 4.0625 by 3.75 inches, but its horsepower depended on model year and configuration—notably vehicle, compression and carburetion. The familiar GTO figures illustrate the difference: General Motors lists 325 hp for the 1964 GTO’s standard 389 and 348 hp for its optional Tri-Power engine.
What is the Pontiac 389 V8?
Pontiac introduced the 389 for the 1959 model year. It became a widely used engine in Pontiac cars, including the GTO and full-size models. The 400 replaced it for 1967; the Automotive History Preservation Society describes the 400 as derived from the 389 architecture with a larger bore.
The 389 is best understood as an engine family used in multiple years and applications, not one fixed-output specification. Carburetion, compression and vehicle application all matter when identifying a particular version or comparing factory ratings.
What are the Pontiac 389’s bore and stroke?
| Specification | Value |
|---|---|
| Displacement | 389 cubic inches, nominal |
| Bore | 4.0625 inches |
| Stroke | 3.75 inches |
| Main journal diameter | 3.00 inches |
| Rod journal diameter | 2.25 inches |
| Production years | 1959–1966 model years |
These dimensions are useful starting points, especially for parts research, but they do not replace checking the actual engine. Wear, previous machining and the specific application can affect what fits a rebuild.
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- Compatibility: Fits for Pontiac 1965-1979 326 350 389 400 455 V8 Engine fit for: 7280 Gaskets
- Part Number: 7156,EDL-7156 //Basic Operating RPM Range: 1,500-6,500 //Intake Manifold Height: 7.450in
- Intake Style: Dual Plane //Part Type:Intake Manifolds,Carbureted //Intake Section Included:Complete
- Engine Block Deck Height:Standard deck //Carburetor Mounting:4-barrel square bore //Intake manifold Color: Natural
- Intake Material: Aluminum(stain) //EGR: No //Package included: 1*intake manifold
How much horsepower does a Pontiac 389 have?
There is no single horsepower rating for every Pontiac 389. Ratings varied by model year, vehicle line and engine specification, so a useful comparison identifies the particular application and cites a source for that year.
| Model year and application | Configuration | Published rating | Source |
|---|---|---|---|
| 1964 Pontiac GTO | Standard 389 | 325 hp | General Motors Heritage Collection |
| 1964 Pontiac GTO | Optional Tri-Power 389 | 348 hp | General Motors Heritage Collection |
| 1965–1966 Pontiac GTO | GTO versions summarized by the source as 335- and 360-hp configurations | 335 hp and 360 hp | Automotive History Preservation Society historical account |
The 1964 figures are GM’s historical claims for the GTO, not universal outputs for every 389. The 1965–1966 figures come from a specialist historical account; consult year- and application-specific documentation when identifying a particular engine. Factory ratings should not be treated as a promise of the output of an aged, modified or rebuilt engine.
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- Vehicle Fitment: Compatible with Pontiac V8 engines including 301, 326, 350, 389, 400, 421, 428, and 455.
- NOTE: Not fit for Pontiac vehicles equipped with Chevy/Oldsmobile engines.
- Important Fitment Note: The HEI distributor cap is approximately 5.5 inches in diameter—larger than the original 4" points-style cap. If converting from a points distributor, please ensure adequate clearance in your engine bay before installation.
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What did the 389 have to do with the GTO?
For 1964, the GTO was an option package for the Pontiac Tempest/LeMans, rather than a separate model line. GM’s Heritage Collection says the package included a high-performance 389, with a more powerful Tri-Power engine available. GM records 32,450 Tempests sold with the GTO package for the 1964 model year.
GM describes the 1964 Pontiac Tempest LeMans with the GTO option package as “the car that started the ‘muscle car’ era.” The 389 helped make that package significant, but its GTO association should not obscure its use in other Pontiac applications.
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- Engine Fitment - This HEI Ignition Distributor Fits For Pontiac Small Block SB Big Block BB 301 326 350 389 400 421 428 455.
- Reference Number - PE326, 1040011, JM6504R.
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What does Tri-Power mean on a Pontiac 389?
Tri-Power refers to an induction setup with three two-barrel carburetors. Pontiac offered it on selected 389 configurations; it is not a separate engine displacement. On the 1964 GTO, GM lists the optional Tri-Power 389 at 348 hp, compared with 325 hp for the standard 389. The Automotive History Preservation Society reports a 360-hp GTO Tri-Power version for 1965–1966. Tri-Power ended with the 389 in 1966.
What years did Pontiac make the 389?
Pontiac produced the 389 for the 1959 through 1966 model years. The 400 followed for 1967. When identifying a car or engine, use the model year and vehicle application rather than relying on the displacement alone; equipment and ratings changed during the 389’s production run.
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- This Bolt Kit Fits All Pontiac V8 326 350 389 400 421 and 455 Engines.(Non-EFI). This is a high quality stainless steel hex bolt kit. The kit includes individually packaged and labeled component kits for the following items:
- Kit comes with components for the Intake Manifold- Valley Cover- Timing Cover- Water Pump- Oil Pan- Oil Filter Housing- Thermostat Housing- Distributor- Coil Bracket- Fuel Pump- Valve Covers- Headers- Crank Pulley – Fan Pulley- Carb Stud Kit.
- The carb stud kit fits Carter, Edelbrock, or Holley Carbs. The studs have an internal hex used to install them in your intake manifold. If you are using a Quadrajet carb, just let us know and we will include a mounting bolt kit for you!
- Header Bolts (3/8-16 x 1 Allen Bolts) And Our Special Small OD Header Washers Are Included With Each Kit! These washers are designed to Clear Large Tube Headers.
What to verify before buying 389 rebuild parts
A rebuild kit may be a useful starting point, but a listing’s compatibility should not be assumed from “Pontiac 389” alone. Confirm the engine’s year and application, then check the dimensions of the engine being rebuilt.
- Identify the model year and vehicle application as closely as possible.
- Measure the bore; the published original dimension is 4.0625 inches, but a previous rebuild may have altered it.
- Verify crankshaft main and rod journal dimensions against the actual crankshaft and the parts being considered.
- Confirm the exact contents and fitment with the seller or manufacturer before ordering; a generic rebuild-kit description does not establish that a specific listing is in stock or fits your engine.
The technical reference lists 3.00-inch main journals and 2.25-inch rod journals as 389 specifications. Use those as reference points, not substitutes for measurement when selecting rebuild parts.
Quick Recap
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- Complete Ignition Distributor in Box (Cap & Rotor Included), E-Z One Wire Hookup; All Electronic Module Components Are Computer Tested Before And After Assembly
- REPLACE PART NUMBER: 1040011, JM6504R, PE326
- COMPATIBILITY: The ignition distributor replacement for Pontiac 301ci 1977-1979, 326ci 1963-1967, 350ci 1968-1977, 389ci 1963-1970, 400ci 1967-1979, 421ci 1963-1970, 428ci 1963-1970, 455ci 1970-1976 small block(SB) and big block(BB)
- SPECIFICATION: This ignition distributor is a magnetic trigger style, mechanical and advanced vacuum type, male cap, and includes an internal coil. One wire installation with high-grade aluminum housing and hardened steel double bushing construction utilizing 4-pin ignition
- FUNCTION: The HEI distributor uses the timing of the rotor to ignite each spark plug, transferring high pressure from the ignition coil to the correct cylinder; The ignition distributor cap houses and protects this rotor and connection
Sources
- General Motors Heritage Collection, 1964 Pontiac Tempest information
- Pontiac technical reference for 389 dimensions and chronology
- Automotive History Preservation Society historical account of Pontiac 389 and 400 engines
- 1964 model reference for Pontiac engine specifications
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