Ok, here's an easy one for you guys. I know what pinging sounds like, I even have some idea of what causes it, e.g., timing, low octane fuel, etc.

I accept the oft-mentioned precaution that excessive pining does engine damage - get rid of it.

But, what causes the noise, and why (how?) does it damage the engine. Is it valves being slapped against the seats, is it wrist pins? What is tapping against what?

Just wonderin'

(No, my truck doesn't ping)
Thanks.

Raul
w/ 81 F-100, I6, SROD, Carter 1V non-feedback carb, no A/C, no PS, no PB, but it gets me where I need to go

 

The noise you hear is the fuel/air mixture being ignited before a particular piston reaches top dead center . The piston is trying to get to tdc but because the spark occurs too early the resulting explosion is trying to drive it back down . Continued pre detonation is very hard on the tops of the pistons .

 

So the noise emanates from where? Piston, wrist pin, rod connection? Or does the explosion actually make the noise, not some physical pieces tapping against each other?

Raul
w/ 81 F-100, I6, SROD, Carter 1V non-feedback carb, no A/C, no PS, no PB, but it gets me where I need to go

 

My understanding is that the sound you are hearing is actually the combustion pressure wave hitting the top of the piston and the cylinder walls. It almost acts like a little hammer. Usually, detonation occurs at a hotspot on the edge of a valve or a piece of carbon in the combustion chamber an then eminates out to the walls and piston top. This pressure wave is what you hear.

In normal combustion you don't hear the wave because it moves the piston instead of hitting it.

This is how I understand it.

Randy

 

Ohhhhhhhh. That makes sense. Thanks.

Raul
w/ 81 F-100, I6, SROD, Carter 1V non-feedback carb, no A/C, no PS, no PB, but it gets me where I need to go

 

In my opinion and from articles I have read... Pinging is a light and usually occasional knocking sound. It doesn't sound very loud and will usually come and go, mostly go, during driving where the engine is under a little more load than usual. this might be going up a hill, hot weather, towing a light load. Most magazines a say occasional pinging is not harmful to the engine, some even say it is a good sign that your computer has advanced to the edge where fuel economy and power is best.

Knock is a stronger variety of ping and usually is nore persistent and is much louder and kind of has a rattle to it. Knock over long periods will pound your bearings, crank, rods and piston tops, eventually it will destroy the crank and or melt the top of the piston. The sound comes from the hammer like effect on the top of the piston resonating through the rods, crank and cylinder walls. Think of ping as a gentle tap with a small hammer, knock as a good thwack with a big hammer.

I personally don't worry about an occasional pinging, and the magazines seem to agree. Over time an engine will get carbon deposits whcih will make it more prone to ping/knock. You might try a gas additive, most magazines recommed using Techron periodically to eliminate the deposits. Most $1 special additives are said to not work according to the magazines. I haven't noticed any benefit to the $1 specials but the Techron does seem to work for me.

If the ping/knock persists you could move up a grade or two in octane. If the knock persists even with premium gas, then there is probably something wrong with the engine, probably heavy deposits or timing issues.

Hope this helps.

Jim Henderson