Projected nose plug caused ?

[Tom68]

550HP 6 litre LS.
Did the plugs eat themselves because they were inappropriate and caused detonation ?
Did detonation caused by whatever eat the plugs ?
Or was it simply too lean under load ?

20221024_173007.jpg

[mag2555]

Can't tell crap from that picture!

Need a much more close up shot of the ground electrode and a very close up shot of the center porcelain.

[Tom68]

Can't tell crap from that picture!

Need a much more close up shot of the ground electrode and a very close up shot of the center porcelain.

They're all but gone.

They would have started out like this.

s-l500.png

[1980RS]

How much total timing? if you are not running nitrous then I would say it's pretty lean to do that.

[F-BIRD'88]

So. how much nitrous was that?

[Walter R. Malik]

550HP 6 litre LS.
Did the plugs eat themselves because they were inappropriate and caused detonation ?
Did detonation caused by whatever eat the plugs ?
Or was it simply too lean under load ?

20221024_173007.jpg

In past experiences, extended reach spark plugs do not last very long in engines that are run at long periods of Wide Open Throttle.

Drag Racing or other type racing where wide open throttle is limited to short bursts, they seem to be just fine on those plugs but, with engines used in land speed engines or offshore type boat racing and such, the tips go away and won't last for whatever reasoning.

[rebelrouser]

How close was the strap to the top of the piston? I have seen the spark jump to the piston if too close. And what was the gap when installed new? It looks like you had a very good ignition system to arc that large of a gap. Remember as the gap increases the KV of the spark increases, more voltage more energy more heat. I don't know about what everybody else does, but on a performance engine, I like .032 to .035 gap on plugs. The .055 to .065 gaps on newer stock engines as mentioned are not that good for WOT performance. And all you need is enough spark to light off the mixture, over building ignition and gaps in my experience does not get you increases in performance. Large KV loads on ignition components also reduces their lifespan. When working on stock vehicles with coil on plus systems for example, almost every failed coil I have seen is hooked to a 150,000 mile spark plug with a huge gap. If you hook a scope and measure the amperage draw of the coil before and after it is easy to see why the coil burnt up.

[Schurkey]

I've seen center electrodes erode. I've seen side electrodes erode.

I've never seen the porcelain erode. I've seen it break, but not erode.

That's new to me. I thought at first the porcelain had been shoved "up" in the shell, but the ink-stamp above the shell doesn't seem to be overly-high.

[Tuner]

That is the result of preignition = extreme heat and detonation = extreme shock both going on at the same time.

As either one can lead to the other it is chicken or egg which first started the situation. The cause may be determined from more information, heat range, load, A/F, ignition timing, engine temp, etc.

[hysteric]

Why is there oil on the threads?

[Tom68]

Why is there oil on the threads?

Installed with a drop of oil on the threads.

[Roundybout]

Surprise it ran as long as it did with 1/4” gap

That’s not a few cycles of detonation or pre-ignition. Whatever the cause it was a lot of heat in that chamber.

[BillK]

Were the last few threads hanging out into the combustion chamber or are they black from the excess heat ??

[Tom68]

Were the last few threads hanging out into the combustion chamber or are they black from the excess heat ??

Heat I guess.

I didn't build it and haven't looked inside yet.

[Tom68]

Can't tell crap from that picture!

Need a much more close up shot of the ground electrode and a very close up shot of the center porcelain.

20221025_182432.jpg