Engine blew up
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Joined: Jul 2002
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From: Long Island, New York
Plug electrodes don't usually break off. They glow, melt, and etch away with each firing stroke.
Think of a cube of steel. Hold a torch in the middle, it will take quite a while to get it hot enough to glow, or melt. Yet if you torch the corner, you can get it to glow, and melt instantly.
The spark plug electrode is the "corner" of the cube in this situation. It is the first part to glow and melt in the combustion chamber when things lean out.
If you have a torched coil pack, then a loose plug is the cause 100%.
There is nothing on the combustion side of the plug to cause a torched coil pack, except for loose plugs. It also torches the spark plug threads and destroys them.
Think of a cube of steel. Hold a torch in the middle, it will take quite a while to get it hot enough to glow, or melt. Yet if you torch the corner, you can get it to glow, and melt instantly.
The spark plug electrode is the "corner" of the cube in this situation. It is the first part to glow and melt in the combustion chamber when things lean out.
If you have a torched coil pack, then a loose plug is the cause 100%.
There is nothing on the combustion side of the plug to cause a torched coil pack, except for loose plugs. It also torches the spark plug threads and destroys them.
Moderator
Joined: Jul 2002
Posts: 22,392
Likes: 1,854
From: Long Island, New York
Originally Posted by robrob' timestamp='1353946789' post='22172006
I have to admit I'm confused here. How does a loose plug lead to damaged valves and pistons?
I could see if you break a valve retainer and drop a valve into the cylinder it could strike the spark plug and damage it and the coil pack but I'm having trouble seeing the reverse happen. Wouldn't a loose spark plug lead to gas blowing by the spark plug and blowing the coil pack off? Once that happened there would be no more spark in that cylinder.
I could see if you break a valve retainer and drop a valve into the cylinder it could strike the spark plug and damage it and the coil pack but I'm having trouble seeing the reverse happen. Wouldn't a loose spark plug lead to gas blowing by the spark plug and blowing the coil pack off? Once that happened there would be no more spark in that cylinder.
Question is how much can leak by plug that is hand tight like my was. It is not like plug was hanging on one thread or blown out.
My guess is plug negatives broke due to ignition/detonation and probably got jammed between valve and seat which in turn can break retainer and valve drops in.
I will know more once I get head of, hopefully in next couple weeks.
Even if you sucked up a lug nut and got it stuck between the valve and seat, it will not break a retainer. It doesn't work that way.
Thread Starter
Joined: Apr 2012
Posts: 907
Likes: 0
From: Reno, NV
Plug electrodes don't usually break off. They glow, melt, and etch away with each firing stroke.
Think of a cube of steel. Hold a torch in the middle, it will take quite a while to get it hot enough to glow, or melt. Yet if you torch the corner, you can get it to glow, and melt instantly.
The spark plug electrode is the "corner" of the cube in this situation. It is the first part to glow and melt in the combustion chamber when things lean out.
If you have a torched coil pack, then a loose plug is the cause 100%.
There is nothing on the combustion side of the plug to cause a torched coil pack, except for loose plugs. It also torches the spark plug threads and destroys them.
Think of a cube of steel. Hold a torch in the middle, it will take quite a while to get it hot enough to glow, or melt. Yet if you torch the corner, you can get it to glow, and melt instantly.
The spark plug electrode is the "corner" of the cube in this situation. It is the first part to glow and melt in the combustion chamber when things lean out.
If you have a torched coil pack, then a loose plug is the cause 100%.
There is nothing on the combustion side of the plug to cause a torched coil pack, except for loose plugs. It also torches the spark plug threads and destroys them.
It does not have to start with loose plug. Loose plug can be step in process.
I have seen it many times on bike engines where plug was still tight, just missing prong.
See spots on valves in #4 where plug is still good and tight.
Thread Starter
Joined: Apr 2012
Posts: 907
Likes: 0
From: Reno, NV
Maybe not as easy on this engine but again seen it on bike engine with aluminum retainer and buckets over them.
Agree once plug is loose pressure will go through it but don't think that is 1st thing that happen here. Maybe plugs are not good, or fuel was bad or ethanol in it, or just running at high revs all the time, or combination of them.
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