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Are Performance Camshafts Legal in the UK?

Conditional

Fitting performance camshafts is legal in the UK as long as the car still meets its emissions standard and passes the MOT. Mild cams are usually fine; very aggressive ones can push emissions or idle quality past the limit.

Why?

Uprated camshafts change valve timing and lift for more power, and there is no rule against them in themselves. The legal test is the same as for other engine work: the car must still meet the exhaust-emissions standard it was type-approved to, and pass the emissions and nuisance checks at the MOT.

Mild fast-road cams generally keep the car within those limits. The risk is at the aggressive end: a big-lift, long-duration cam can lump the idle and raise emissions enough to fail, especially on a car with tight modern emissions targets.

So the summary is that performance cams are legal if the finished car still passes emissions and runs cleanly; a cam so wild that it fails the tailpipe or nuisance test is not. As an engine change, tell your insurer too.

What decides if it's legal

  • The car must still meet its exhaust-emissions requirement.
  • It must still pass the MOT emissions and nuisance checks.
  • Aggressive cams can roughen idle and raise emissions, which is the risk.
  • Declare the change to your insurer.

Does it depend on your car?

How much cam a car can take before emissions suffer depends on the engine and its management. The legal bar, meeting emissions and passing the MOT, is the same for all of them.

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Sources

This page is general guidance, not legal advice, on the rules in the UK for performance camshafts. The detail varies by exact vehicle and changes over time - confirm with your insurer and the latest DVSA and GOV.UK guidance before modifying.