My LS1 developed a valvetrain tick — is it serious?

Not an emergency, but don't ignore it. A tick from the valvetrain is usually a clearance problem: a lifter not pumping up fully, a worn lifter, a bent pushrod or a loose rocker. Left alone, a failing lifter can wear the cam lobe or rocker it rides on, and in the worst case come apart and send pieces through the engine — that's where the real cost comes from.

Quick checks to tell a lifter tick from something worse:

• Where it comes from: a lifter tick is up in the valve-cover area; rod knock is deep in the block or oil pan. A long screwdriver (tip on the valve cover, ear on the handle) or a mechanic's stethoscope helps.
• Cold vs hot: lifter ticks are often loudest on a cold start and fade as oil pressure comes up. Rod knock doesn't change much with temperature.
• Load: rod knock gets louder under load and with rpm. A lifter tick is usually most obvious at idle and may quiet down with rpm.
• Kill one cylinder at a time: if the noise drops out when one coil is unplugged, suspect that cylinder's rod bearing. A lifter tick keeps going because the valvetrain still moves.
• Rule out an exhaust leak: a leaking manifold gasket can sound just like a tick, especially cold. Look for soot at the ports.

First things to try for a lifter tick: check the oil level (too low or overfilled — overfilling can aerate the oil and collapse lifters), change the oil and filter with the correct grade, and pull a valve cover to look for anything obviously broken or loose.

If the tick stays after fresh oil, or you find a loose rocker or bent pushrod, plan to fix it before it takes the cam with it. More: piston slap vs lifter tick vs rod knock.