Hom much hp in a 78 trans am?

The horsepower of a 1978 Pontiac Trans Am varied significantly depending on the engine option chosen. There wasn't just one horsepower rating. The most common engines and their approximate horsepower ratings are:

* 400 CID (cubic inch displacement) V8: This was the most common engine and usually produced around 180-220 horsepower. The exact output varied slightly based on the specific carburetor and other factors.

* 6.6 Liter (403 CID) V8: A less common option, this engine might have produced slightly more horsepower than the 400 but the exact figures are hard to pin down without a specific model configuration.

Therefore, there's no single answer. You need to know the specific engine installed in that particular 1978 Trans Am to determine its horsepower.