How do you increase horsepower on a 1965 Pontiac 389?

Answer 1

There are many ways to increase HP on older engines. The improvement depends on your wallet and what you're willing to do yourself.

1. Make sure the air filter is clean. Dirty filters don't flow as much air and choke the engine which also wastes gas.
2. Run a cold air intake hose to a point alongside the radiator or below it. This draws cooler, denser air into the engine.
3. Ensure that the engine is tuned as perfectly as possible. A 1965 will have ignition points. Set the dwell angle between 28-32 degrees. Outside the range will cause the spark to be too weak or burn the points which also weakens the spark.
4. Buy quality spark plugs and wires. They don't need to be racing grade, but cheaper wires leak voltage through the sheath which may cause them to ground on exposed metal nearby. Ensure the plug gap is correct.
5. Install a 4-barrel carb on the engine. This may require installation of a larger fuel pump and fuel line. Do your homework first.
6. Swap in a more aggressive camshaft and intake manifold. If you're swapping the carb you've done half the work for removing the intake too.
7. Install headers and dual exhaust. While pricey, this provides the largest increase in HP.
8. The Nuclear Solution is to overhaul the engine entirely: cam, lifters, intake, carb, pistons, etc., complete with blueprinting and balancing. If you go this route be prepared to spend over $5000. An engine of this type was listed on Ebay for $8000.