For mild street engines, stock valve springs are more than adequate. But if you've screwed in a big bumpstick for strip-banging or banzai runnin', then pay attention. Our plan was simple: Install a ...

We may receive a commission on purchases made from links. Is your car misfiring, having trouble starting, or idling rough? Are you wondering if the problem is one of your coil packs? If you're like ...