The Stovebolt Site Forums The Shop Area Engine Shop Can valves affect pinging?

Dumb question for the day... I know pinging is mostly about timing, but if valves are not adjusted properly, can that cause pinging?

Dennis

Nope- - - -"ping" is slang for detonation- - - -the noise caused by two flame fronts traveling opposite directions across the combustion chamber. The second flame front is caused by something called "pre-ignition"- - - -burning of the fuel begun by something other than the spark plug. The source of the preignition can be a glowing piece of carbon in the combustion chamber, too lean mixture which causes the fast-burning flame front to push a pressure wave ahead of it and cause the mixture to "diesel", or several other factors. Too-early ignition timing and/or too low octane gasoline for the compression ratio can also contribute to detonation. Once the second flame front begins, the noise created by the flame fronts slamming together is loud enough to be beard through the cylinder walls, coolant, and cylinder head structure.

Gasoline engine detonation is the most powerful destructive force (other than nuclear) known to science. It is much more destructive than an equivalent weight of Dynamite, TNT, C-4, etc.
Jerry

Thanks teach. A thorough answer as always.

Dennis

I think he heard something like "increasing your valve lash will delay intake valve closure, and increase cranking compression".
It will, but not enough to ping unless:
1. 1/16" lash
2. engine is already borderline

"Delay"??????? I'd like to see that demonstrated. It seems that it would shorten duration and make the valve close sooner- - - - -which could increase the compression stroke and compression pressure- - - -in theory.
Jerry

Lash will effect the opening timing and closing timing of the valve. More lash equals shorter time valve is open, less lash, valve is open longer.

A valve itself can cause pinging, ONLY if it has a carbon build up enough to glow just as Jerry explained, usually around the edges. I could see how to much lash could possibly cause some pinging if the valve doesn't open enough to fully fill the cylinder, thus causing a lean condition, but, it would have to be pretty far off I suspect.

Ooppsss!
Shorten is of course correct.

I recall reading somewhere that a heat riser valve stuck in the closed position can cause excessive pinging under load. is this possible?

Yes- - - -it raises the temperature of the intake mixture to the point the fuel/air mixture is easier to compression ignite before the spark plug fires. It's similar to how glow plugs in a Diesel engine preheat the air so the compression can raise the temperature enough to light off the fuel. Diesels need to raise the combustion chamber temp to around 1,000 degrees F. before the fuel will light off. Preheating the intake air in cold weather helps that happen, and it's also why starting fluid should never be used on a glow plug equipped engine. Ether and red hot glow plug filaments don't play well together!
Jerry

Valves that have been ground to a point where the edges are thin can cause pre-ignition.
George