How much real power?

430 HP? Although rated at 430 horsepower by the old method, Chevrolet never released actual power figures for the as-installed production ZL-1 engine. Numbers were tossed around for years until Bill Porterfield decided to find out. Bill had acquired an original block from one of the cars and enough NOS parts to complete another engine. The engine was subjected to 5 levels of test. RPM was limited to 6750.

Engine                       Test
Configuration                Result
---------------------------- --------
All accessories, production  375.7 HP
exhaust manifolds, Camaro
chambered exhaust system,
36 degrees timing

As above with 2-1/8" headers 418.9 HP
replacing the manifolds

Air cleaner, alternator, AIR 447.2 HP
pump removed

Carb re-jetted, timing set   444.2 HP
to 39 degrees

Chambered exhaust system     523.6 HP

The ZL-1 was a legitimate 500+ horsepower engine.

Others have recently built ZL-1's with similiar or higher results. Several have dynoed in the 540-550 HP range. Modern components like piston rings may be the cause of the slightly higher performance.