Are Performance Camshafts Legal in the US?

Conditional

Performance camshafts are legal in the US only if the engine still meets its emissions standard afterward. Cams change how the engine breathes, so in California and CARB states they need a CARB Executive Order, and anywhere a cam that raises emissions is not compliant.

Why?

A camshaft swap alters valve timing and lift, which changes the combustion and the emissions the engine produces. That places it under the aftermarket-parts emissions rules rather than treating it as a free internal change.

In California and the CARB states, an emissions-relevant part like a performance cam generally needs a CARB Executive Order (EO) to be street-legal, and a smog check can reject a car running non-approved cams. Outside CARB states the federal test is whether the car still meets its emissions standard.

So mild cams that keep the car within its emissions limits, and that carry an EO where one is required, can be road-legal; aggressive cams that push emissions past the standard or fail a smog check are not. This is one where a rolling-road tune and the emissions result matter as much as the part.

What decides if it's legal

Camshafts change how the engine breathes, which is emissions-relevant.
The car must still meet its emissions standard after the change.
In California and CARB states, performance cams need a CARB EO to be street-legal.
A cam that raises emissions or defeats controls is not compliant.

Does it depend on your state?

Yes. In CARB states performance cams need a CARB Executive Order to be street-legal; in non-CARB states the test is whether the car still meets its emissions standard. Either way a cam that raises emissions is not compliant.

Related legality guides

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Sources

This page is general guidance, not legal advice, on the rules in the US for performance camshafts. The detail varies by exact vehicle and changes over time - confirm with your insurer and the EPA, NHTSA and your state DMV before modifying.