Burned valves

Decolliber · 12-16-2002, 08:27 AM

A recent thread on valve adjustment mentioned that making them too tight could cause burned valves. Now I am obsessively wondering if I checked my adjustments enough times last time I did the valves. Can someone tell me exactly what this means? Is it the stems or the heads of the valves that get burned? What are the long term consequences? Are there noticeable symptoms of burned valves?

JWest · 12-16-2002, 08:51 AM

If the valve is adjusted too tight, then the valve head does not contact the seat (remain closed) for as long a time as a correctly adjusted valve. This time of contact is when the heat is transferred from the valve to the seat and on to the head to be disipated by the fins/cooling air.

The valve head could overheat and cause a burned valve.

Superman · 12-16-2002, 08:53 AM

Relax. If you got your feeler gauge between the adjusting foot and the top of the valve, then you won't have this problem. Do not remove spark plugs as part of the process, since this can drop carbon onto the exhaust valve seat, resulting in adjustment that is WAY too tight. If you ever had to turn the adjusting screw in too far, I would hope you would stop and check things out.

The valve head has to return to the seating surface on the head. It rests there, and delivers its heat into the head that way. If it were not returning to the seat, then it would stay hot and burn.

Valves that are adjusted too tight, or burned valves, do cause engines to run poorly. Popping and knocking and stuff like that. Unless you remove plugs, or unless you failed to get your feeler gauge between the valve stem and the adjuster, I'd suggest yo find something else to worry about.