How long time and how extensive much the piston be exposed to detonation before you can se trace on the plugs?
Is one small tip-in detonation enough to leave marks on the plugs? And is plug reading for detonation "fool proof"?
Is detonation the only condition that leaves the classic signs as, black dots or even metal flakes on the plugs? Or can something else leave the same kind of signs, worn vavleseals, bad rings and blow-byes, etc etc, and foul you?

Thanks

 

1) Depends on how severe it it.

2) Depends on the experience of who's reading them, not to metnion lighting, and having good enough vision. There are a few guys, that are just incredible.

3) Oil can at times be a fooler, but usually there's enough evidence to qualify the specks as detonation when it is in fact detonation. The trouble with oil is that it also promotes deonation, so understanding all that you're seeing is important.

 

I wish I had more GOOD plugs to look at . Instead I'm usually subjected to some mechanical problem. I get black, wet black, chalky white, and grounded electrodes all the time .
The one thing that I haven't seen much talk about is plug temperature selection. How does one go about picking a spark plug for a custom engine? Are there any pictures showing the difference between a hot, good, and cold spark plug? It tooke me years to finally break down and go to a step cooler spark plug. I don't know why it likes it but it does... maybe I'm burning some oil that I don't know about or the 87 octane is catching up to me, .
Do you have any books that go into detail about plug readings?

 

In general, run the coldest plug that doesn't foul. This can also mean swapping plugs if going racing instead of street driving.

RBob.

 

Thanks. That's what I've been doing. The larger duration cams do seem to be more sensative to spark plug selection. It makes sence that they would since at idle the have poor cylinder fill (would want a warmer plug) and under peak power, need a cooler plug.
I wonder if the newer longer lasting plat tiped plugs have a better resistance to fouling. Or maybe it's my weak ignition system that's given me the most headaches.

 

That's why they went to the projected nose design.

Not that I've seen, they're strickly in response to the EPA low maintance mandate. The logic seems in part to be charge enough to replace them at least once under warranty, to get the 100K mile service life, IMO. I've never seen any advantage to them in a car with a good ignition system.