How can you increase HP in an 1986 Corvette without getting into the engine?

You can't significantly increase the horsepower of a 1986 Corvette without modifying the engine itself. Any gains outside of engine work will be minimal and potentially even negligible. Things you *can* do that might *slightly* improve performance (and might be perceived as a HP increase, though it's not actually a horsepower gain at the crank) include:

* Improve Air Intake: A better air filter (high-flow, but make sure it's properly sized and doesn't negatively affect air metering) might allow slightly more air into the engine. This is a minor gain at best.

* Improve Exhaust: A less restrictive exhaust system (headers, cat-back system) can slightly reduce back pressure, leading to a small improvement in power. However, this is more noticeable in terms of throttle response and feeling more powerful rather than a significant HP increase on a dyno.

* Optimize Ignition System: Ensure your ignition system is in perfect working order with new wires, plugs, and a properly functioning distributor. A weak ignition system robs power, so fixing it *restores* lost HP, rather than adding it.

* Lightweighting: Removing unnecessary weight from the car (spare tire, heavy sound system, etc.) improves the power-to-weight ratio, making the car *feel* faster, even if the engine's HP remains the same. This is not a horsepower increase but an improvement in acceleration and handling.

It's crucial to understand that these modifications are relatively minor and won't drastically increase the horsepower output. Any noticeable HP gain requires internal engine modifications such as camshaft upgrades, performance heads, or forced induction (turbocharger or supercharger).